| Starting on my first amp, have some questions - Click HERE for Original Thread |
| Saurav |
Well, that was a pretty obvious thread title :) The amp I'm building is the JE Labs/Angela SE 2A3 with the SRPP 6SL7 driver and "my own" PS using a 5AR4. Questions:
* What do you think of this layout?
I had no idea the transformers would be that big, or I would have ordered a 17"x14" chassis (that's a 17"x10"). I was thinking about a layout that's symmetrical around a center line with the PS in the middle, but since I can't put the PS transformer, rectifier tube and PS choke in a straight line without making everything almost touch, I think that option is out (I could still leave the rectifier offset from the line of the transformer/choke, but that won't look very nice). With this layout, I'd put the power switch on the left front, and IEC connector and fuse on the left back. Haven't decided how to do the binding posts and RCAs yet, they'll be somewhere on the rear right. Maybe RCAs on the inside and binding posts on the outside. The filament transformers will be under the hood, probably on the left wall or between the PS transformer and choke.
The other layout option would be to move the 6SL7s closer to each other, and then put my hum balance pots on the outsides of the 6SL7s, in front of the 2A3s. That would let me adjust them without having to reach around hot tubes, but would that bring heater currents too close to the 6SL7s?
* Transformer polarity/phase - how important is it to have the 2 filament transformers in phase? Is there any way to tell other than hooking them up and measuring the voltage difference between leads? For the PS choke, does it matter which way I connect it?
* 125ESE wiring diagram - mine didn't come with any, but I'm assuming that I'll be able to find one online somewhere, probably at the Hammond site.
* Transformer grounding - this is important, right? The PS transformer and choke seem to have paint on the outside casing, so I'm not sure if just using bolts and toothed metal washers will make electrical contact. Do I need to scrape the paint off near one of the bolt holes?
* Power up test sequence - does this make sense?
- Power up with no tubes. Make sure secondary voltages are as expected, i.e. the secondaries have been wired correctly.
- Power off, insert all tubes except rectifier, power up. Verify that all filaments light up, filament voltages look good, and HT secondary voltages look good.
- Power off, remove all tubes, insert only rectifier tube, power up. Verify rectifier filaments heat up, and B+ looks correct at output and driver tube plate pin sockets. Voltages will be high because no current is being drawn (this is the step I'm not sure about... is this a good idea?)
- Finally, power up with all tubes inserted.
Thanks a lot in advance, and I'm sure this will be the first post of many.
Saurav |
|
|
| Magnetmaz |
I'm not so cool with all the Trafos so close to the tubes, but.....i think you can pull it off. At least the 6SL7's arent sitting on TOP of any of them.
Good luck to you, Saurav,
-Maz |
|
|
| Saurav |
| Well, I could get another enclosure and make that the PS and use this one only for the audio circuitry. I'd rather do it right the first time than have to re-do everything because it's too noisy. |
|
|
| PassFan |
| If you have any doubt about having enough room, order what you need now. You can probably return the chassis before you punch holes in it. Keep us informed :) |
|
|
| Colt45 |
| looks like plenty of room to me. |
|
|
| JOE DIRT® |
your layout looks good to me....all your wiring will be short which is important...I dont feel that the transformers will affect the tubes....and on another question you asked the transformers dont need to be grounded...just the chassis
DIRT® |
|
|
| Saurav |
OK, if I move the transformers right to the edge of the chassis, I can just about fit the rectifier between the PS choke and transformer. That gives me around 3/4" clearance on both sides of the paper box for the rectifier tube, so it'll be a hair more for the actual tube.
Is that better? I could also rotate all transformers and have the 125ESEs along the back edge. That would put them a little closer to the PS trafo, but give a little more room for the 2A3s.
I'm sorry about the flash reflection off the chassis, the protective plastic layers are still on.
And this is the largest aluminum chassis that Angela carries, I double checked that. So I could exchange it for a bigger steel chassis (which would be harder to drill and Morgan Jones recommends against using steel), otherwise returning it will be a little difficult, since the first thing I did was to tear up my invoice and throw it away :) (it had my credit card number on it). |
|
|
| Wardsweb |
You should be fine. A trick for determining the best alignment of the power and output iron is to power up the power transformer and hook a volt meter to the input side of the output iron and measure mV AC. Your looking for the lowest number you can achieve by turning them in different configurations. This is help to minimize induced hum.
Here is a heavely modified Dynaco Mark 3, and you thought yours was close. :bigeyes: |
|
|
| Saurav |
| quote: | | Here is heavely modified Dynaco Mark 3, and you thought yours was close. |
Well, yes, but that was probably designed by someone with a little more experience than me :)
I'll try out the voltmeter solution, though it would make me nervous to have all the secondaries unconnected. I guess I could wire-nut each one individually. |
|
|
| Ryder |
I don't have the experience of a lot of folks here but how bout a breadboard instead of committing it to final form. It is a nice way to experiment with placement, wire length ectc...and how it effects things. I've been messing around with this stuff for a year and while I got it off the drawing board I have not gotten off the breadboard to date. It makes those almost inevitable mistakes easier to handle, allows you to focus on sonics, and makes tweaks and changes less traumatic too. At least, I think, for a beginner.
Cheers
Craig Ryder |
|
|
| arnoldc |
saurav,
try this
+--------------------------------+
|................................|
|..OOO........PPPPP.........OOO..|
|..OOO........PPPPP.........OOO..|
|................................|
|...6.........CCCCC..........6...|
|...2.. ........R............2...|
|................................|
+--------------------------------+
where OOO is the OPT, PPP is the power trafo, CCC is choke, 6 is 6SL7, 2 is the 2A3 and R is the rectifier.
it seems to me you have enough room ;)
here's the wiring diagram of the 125ESE - http://users.starpower.net/je2a3/125SE-1.jpg
* Transformer grounding - *
I didn't do that
* Power up test sequence - does this make sense?
- Power up with no tubes. *
right
- Power off, insert all tubes except rectifier, power up. *
right
- Power off, remove all tubes, insert only rectifier tube, power up. *
Yes, your B+ will be off
- Finally, power up with all tubes inserted.
I'd like to add that you do some resistance checks just to make sure you don't have a cold solder.
Good luck, it will be fun. |
|
|
| Saurav |
| quote: | | where OOO is the OPT, PPP is the power trafo, CCC is choke, 6 is 6SL7, 2 is the 2A3 and R is the rectifier. |
Would you mind explaining why you suggest this layout? I had R between PPP and CCC because that's how the wiring will flow. Also, why do you recommend placing the 6SL7 closer to OOO than the 2A3?
| quote: | | I'd like to add that you do some resistance checks just to make sure you don't have a cold solder. |
Of course, that's before I power it up for the first time.
So it looks like many people don't bother with grounding the transformer frame?
Ryder,
I was thinking about breadboarding, but I don't have a dedicated space to work in, so that will be difficult to pull off. I'm toying with the idea of a "semi-breadboard" kind of a thing, where I fix the locations of the components, but hook them up using clip leads first to make sure everything's correct, and solder the connections later. That will make it easier to leave everything in a corner of the living room when I'm not working on the amp. |
|
|
| Saurav |
OK, I think I get it - that way the rectifier will have more airflow around it, because it doesn't have iron on two sides. And it's probably the same reasoning for the 2A3 as well.
I'll try that out and see how it looks. |
|
|
| EC8010 |
I liked the layout of your second set of photos better, but how about doing it like this? The (hot) 2A3's are now at the edge of the chassis and can cool better, you have shorter wiring in the PSU, the input valves are close together (makes input wiring and earth busbars easier) and a long way away from the PSU, it's symmetrical (almost) and all the glowing glass is at the front where it belongs. The slight downside is that the rectifier is still in the middle of the chassis, but it won't get as hot as the output valves. If you were confident of your metalwork, and worried about its temperature, you could drill ventilation holes around it. I probably wouldn't bother.
My drawing suggests that the mains transformer's coil points at the input valves. Of course it doesn't. Its coil should point horizontally. |
|
|
| Joel |
Although it often has no audible effect, you should as a rule make sure the power transformer 'bell' ends are grounded to the chassis. Just scrape the paint off the bottom of one "foot" on each side. I do this in all my amps, and it sure doesn't hurt.
Joel |
|
|
| Saurav |
You know, that's almost exactly how the amp is laid out on the Angela website. My only hesitation with that layout is that the RCA connectors and binding posts would need to be on the sides of the enclosure, and the power switch would need to be in the back. I think I can live with that though - the 2A3s are taller than I expected, and this amp won't fit in my audio rack, so it'll have to go on the top shelf. That will help with cooling, and it'll also be easier to reach around to the back of the amp.
| quote: | | If you were confident of your metalwork |
That's the thing I'm least confident about, followed by my spray painting skills. Would you recommend ventilation holes around the 2A3 tubes? I think I could manage that if I didn't put the holes too close to the socket hole.
| quote: | | My drawing suggests that the mains transformer's coil points at the input valves. Of course it doesn't. Its coil should point horizontally. |
Could you explain that please? I'm assuming that the large rectangle in the middle indicates the laminations, and the two smaller rectangles on the sides indicate the bell endcaps? |
|
|
| EC8010 |
| Agreed. This comes into the category of, "It doesn't cost anything to do it, and I'm not sure if it makes a difference, but I certainly wouldn't like to spend hours finding that its absence was the cause of a problem." |
|
|
| Saurav |
OK, I was looking through the Bottlehead boards about transformers and metal top plates because I remember seeing some discussions on this in the past. It seems like a lot of people there mount the transformers on rubber/vinyl grommets to mechanically and electrically isolate it from the chassis, and run a drain wire from the frame to earth/safety ground. That seems to make sense to me, and a ground lug placed under the transformer's foot with the paint scraped off the underside would be an easy way to implement that ground connection. That will also allow me to paint the chassis without worrying about masking off the transformer mounting holes to maintain electrical contact.
Thanks for that tip. |
|
|
| EC8010 |
| quote: | Originally posted by Saurav
You know, that's almost exactly how the amp is laid out on the Angela website. |
I didn't look, honest.
| quote: | | My only hesitation with that layout is that the RCA connectors and binding posts would need to be on the sides of the enclosure, and the power switch would need to be in the back. |
What's wrong with having the RCAs at the front, between the input valves, or are you going to put a volume control and selector switch there? The binding posts could go at the sides, or the back (twist the leads to them). The back is the best place for the mains switch, makes you think harder about turning it off...
I wouldn't bother with ventilation holes. With the 2A3s at the edges, they will cool nicely, and drilling ventilation holes exposes less-than-perfect metalwork.
Your assumption is right. For your mains transformer and choke, the coil is oriented along the direction of the laminations. The mains transformer should not point its coil at the input valves, but the choke produces a rather smaller leakage field, so it can. |
|
|
| Saurav |
| quote: | | I didn't look, honest. |
I didn't think you did :) What I was trying to say was, if two people independently arrived at the same (or similar) layout, there's probably a reason behind it.
| quote: | | What's wrong with having the RCAs at the front, between the input valves |
Just the cable routing for the interconnects. Of course, I could rebuild my linestage and put one set of outputs in the front, and run cables up the front of the rack. Right now, all cables are in the back, so putting the RCAs in front would mean running cables beside, or over, the tubes. Most of my interconnects are DIY with fairly stiff coax, so this may not work very well, as it'll be hard to lay the cables down beside the chassis.
| quote: | | and drilling ventilation holes exposes less-than-perfect metalwork |
Good point that I hadn't thought about. |
|
|
| EC8010 |
| quote: | Originally posted by Saurav
Just the cable routing for the interconnects. Of course, I could rebuild my linestage and put one set of outputs in the front, |
Yuck. It's a problem. How about putting the RCAs on the top, in the middle, and curl your interconnects gracefully over the top? Not ideal, I know, but I don't think you're going to get an ideal position for the RCAs. |
|
|
| Saurav |
Either that, or put them in the front corners, or the side surfaces near the front of the chassis, and see if the ICs will bend around the sides of the chassis.
Thanks for the ideas. |
|
|
| jmpsmash |
| you should also consider leaving more space for the 5AR4. if you want to tweak it using larger rectifiers like the 5u4g, you need more space there. |
|
|
| Saurav |
| How much bigger is a 5U4G compared to a 5AR4? And what would be the advantage of using it, i.e., why would it make a better rectifier than the 5AR4? |
|
|
| arnoldc |
| quote: | Originally posted by Saurav
How much bigger is a 5U4G compared to a 5AR4? And what would be the advantage of using it, i.e., why would it make a better rectifier than the 5AR4? |
My RCA 5U4G is close to the size of the 2A3. It did give me a problem on by beta 300B as it nearly touches the choke, so I changed it to a 5AR4 (of course adjustments made to compensate for higher voltage due to lower voltage drop of the rectifier).
If I have a chance and applicable to the circuit, I'd go for a 5AR4 due to the slow voltage rise inherent on this tube. |
|
|
| Saurav |
| That slow B+ rise is why I decided to build my PS around the 5AR4. That way I can have a single power switch, which means maybe my wife won't be too intimidated by the amp to actually use it :) |
|
|
| EC8010 |
If you really want a slow power-up, why not use TV damper/efficiency diodes? They have stunning insulation between their heaters and the cathodes, which slows down their warm-up time. Most have top-cap cathodes, but the 12CL3 brings all its connections out onto a B9D (Magnoval) base. It needs a 12.6V heater though. Perhaps you could use a little 12V toroid under the chassis?
There was a thread on these diodes on this forum recently...
Ah, you should have specified that it was to be used by other people...
How about a rotary mains switch? That way, you can put the electrical switch at the back (where it belongs) and extend it with a 1/4" shaft to the front. |
|
|
| Saurav |
Damper diodes - I read those discussions, but decided to stay with more conventional rectifiers for my first attempt. I can always try that as an upgrade. How large are those tubes?
| quote: | | Ah, you should have specified that it was to be used by other people... |
Well, one can always hope :) Once I'm off the internet, this is a pretty lonely hobby...
The rotary mains switch is a good idea. I thought of another option, I could put the power switch on the side panel of the chassis, in the back near the PSU circuitry. Since this amp is going to be on the top shelf of my rack, that should be fairly easy to reach. Also, it'll make for an interesting look, because I can put binding posts and RCA connectors all on the side panels.
Has anyone made carrying handles for their amps? All I have is a little 300V 200mA Hammond power transformer, and this is already heavier than anything else I own. I thought about screwing on carrying handles to the side surfaces (when I was thinking of putting switches and connectors on the back), but I'm not sure if that will put too much of a flexing stress on the aluminum with the heavy transformers in the middle of the chassis. Also, with the transformers now off to one side, the weight distribution becomes uneven. Maybe I should just not worry about this. Or put in one handle in the back, close to where the weight will be. |
|
|
| EC8010 |
12CL3 is remarkably small - smaller than a 6SL7.
Experience with unenlightened/unenthusiastic users shows that that the on/off switch has to be at the front or it will not be used...
Just you wait (weight). Bigger amplifiers require even weight distribution and handles. This is a problem for the future. |
|
|
| Saurav |
FWIW, here are images of the amp from the Angela website:
As you can see, almost identical to your layout, just with all the iron rotated by 90 degrees. |
|
|
| Saurav |
| quote: | | 12CL3 is remarkably small - smaller than a 6SL7. |
Hmm... then the hole I drill for the 5AR4 socket will probably be too large. I think I'll try this later... unfamiliar territory.
| quote: | | Experience with unenlightened/unenthusiastic users shows that that the on/off switch has to be at the front or it will not be used... |
Well, then I guess she'll continue to listen to music on the computer like she does now. Makes me feel a little guilty, but not too much ;) |
|
|
| EC8010 |
There's very little difference. Their version allows better cooling, but if you move the 2A3 up the chassis, my layout might be almost as good. In terms of electromagnetic induction, I think my layout may be better. There's really not much in it. Moving the 6SL7 closer together is worthwhile because it allows good point to point wiring.
Go for the efficiency diodes now. They're difficult to retrofit.
You need to convert your other half. What are you going to do when you want to introduce a pair of huge transmission-line loudspeakers into the living-room? You will need to be able to convince her that they are worthwhile, and that starts with education now... |
|
|
| Saurav |
| quote: | | In terms of electromagnetic induction, I think my layout may be better. |
That's the one I'm going with. I don't think heat will be that much of an issue, it's hum that I'm more worried about.
| quote: | | Moving the 6SL7 closer together is worthwhile because it allows good point to point wiring. |
I was planning on using both triodes in a single envelope as the upper and lower triodes of the SRPP. So, each 6SL7 serves one channel. Why would having the tubes close together make a difference? I'll be running individual grounds for each channel too, FWIW.
| quote: | | Go for the efficiency diodes now. They're difficult to retrofit. |
I think I'll try that in a future project then, assuming I build any more amps :) I've already bought the 5AR4. Where can I buy a 12CL3? I didn't find any on eBay, nor on Triode Electronics.
| quote: | | You need to convert your other half. What are you going to do when you want to introduce a pair of huge transmission-line loudspeakers into the living-room? |
LOL!! Well, she's living with this right now, so...
I think I'm pretty lucky, in the overall scheme of things :)
Those are the sealed "bookshelf" versions of the Adire HE12.1s. 96-97dB, 12" woofer with coaxially mounted 1" compression driver. |
|
|
| fragman56 |
How do you like them? I've seen some good reviews. Please tell more about the speakers.
Interested,
Rick |
|
|
| EC8010 |
| quote: | Originally posted by Saurav
I was planning on using both triodes in a single envelope as the upper and lower triodes of the SRPP. So, each 6SL7 serves one channel. |
I think you might do better to use one valve to cope with the low cathode voltage stuff, and another where the cathode is at a higher voltage. Stereo crosstalk within valves is much exaggerated.
A quick search brought up 12CL3 at very reasonable prices.
Education is a wonderful thing, and if you can persuade your other half to use the existing kit, who knows what you can get away with later? One step at a time.
Making stereo amplifiers with low hum tends to be awkward unless you have a common earth bus bar, hence the comment about moving the 6SL7s closer together. |
|
|
| Saurav |
| quote: | | I think you might do better to use one valve to cope with the low cathode voltage stuff, and another where the cathode is at a higher voltage. |
That would help because I wouldn't have to use a voltage divider to keep the heater midway between the cathode voltages of the two SRPP triodes. However, that would also require yet another transformer under the hood, because the two triodes would now have their cathodes at very different potentials, and I couldn't feed them from the same heater.
OK, I found 12CL3s at thetubestore.com, and they are cheaper than the 5AR4 that I bought. I'll definitely try that out in the future.
| quote: | | Education is a wonderful thing, and if you can persuade your other half to use the existing kit |
She tolerates it, I'm not sure how much she uses it though. One of her friends told her she's very "accomodating" to allow those speakers in the living room.
Fragman56,
I like them a lot. Their strengths are liveliness and dynamics, especially in the midbass. Compared to my last speakers (GR Research Paradox 1s), they aren't quite as refined in the midrange and treble. I've tweaked mine quite a bit from stock, and those tweaks helped quite a bit. My crossover has been modified to raise the upper treble (12KHz+) by a couple of dB, I've removed the dustcap from the woofer and coated it with shellac, liberally used polyfill on the basket legs and around the motors, and my amps have a 75Hz high pass filter on them (cap between the input RCA and tube grid). IMO all of these have helped, some more than others. |
|
|
| EC8010 |
| quote: | Originally posted by Saurav
However, that would also require yet another transformer under the hood, because the two triodes would now have their cathodes at very different potentials, and I couldn't feed them from the same heater. |
Um. Not quite. Nothing has changed. You've just exposed a slight weakness in the original design. Fortunately, Octal valves can tolerate this treatment, but it would be nicer not to hammer them.
Believe me, education is a good thing. Your other half is perfectly capable of hearing how much nicer your system is - but you're going to have to make it easy to use. This isn't a disadvantage - you get it too! |
|
|
| Saurav |
| quote: | | Um. Not quite. Nothing has changed. You've just exposed a slight weakness in the original design. |
Hmm... are you saying that I still use the voltage divider to raise the 6V winding up to around 80V, and run that to both tubes? Then the heater will be high for one whole tube and low for one whole tube, instead of being high for one triode and low for the other triode in the same envelope. Did I understand you correctly?
| quote: | | Fortunately, Octal valves can tolerate this treatment, but it would be nicer not to hammer them. |
So you're saying that it would be nice if I used a second 6V transformer so that I could keep heater voltage close to cathode voltage on both tubes, but it's not essential? Maybe I should just go ahead and do that... I saw a 6V transformer with sufficient current rating on eBay once for just a few bucks. |
|
|
| EC8010 |
| Yes, right on both counts. |
|
|
| Saurav |
Um... a really dumb question. When I'm looking at a tube pinout like this:
 
Is the pin numbering looking down from above the socket on the side the tube goes, or looking up from under the socket on the side where the solder tabs are? |
|
|
| EC8010 |
It's from underneath. Many years ago, I made some PCBs with ICs. But IC diagrams show their pins from the component side of the board.
Edit: John, I'd never noticed that ICs and valves count their pins in the same direction. You learn something every day. |
|
|
| Saurav |
Thanks a lot. I need this to decide how to orient my sockets so the heater wiring doesn't have to go around the socket, and that will determine where I drill the holes for the bolts.
Do people usually cut transformer leads to size, or leave them at their original size? The latter would facilitate reusing the iron in future projects, but would make for messier wiring dress. |
|
|
| dhaen |
| Valves and IC's both increment pin number clockwise, looking from underneath:rolleyes: |
|
|
| dhaen |
| It's sometimes possible to push some lead length back into the shroud. |
|
|
| EC8010 |
Cutting transformer leads is all down to how confident you are. I try to route them so that there is enough lead left if they have to be salvaged.
The worst possible thing to do with heater wiring is to wire round the socket on one side with the incoming, and round the other with the outgoing. You've just made a loop aerial with the valve in the middle. If you have to loop round to a tag on the far side, do the incoming and outgoing wires on the same side. |
|
|
| arnoldc |
| quote: | Originally posted by Saurav
Do people usually cut transformer leads to size, or leave them at their original size? The latter would facilitate reusing the iron in future projects, but would make for messier wiring dress. |
hi, i guess you've got to make a decision now if you will be re-using your transformer. specially with the 125ESE, i did not cut them because i've used them in 4 different amps already (with positive results on all) with varying physical designs. besides, the wires of the 125ESE are not at all that difficult to coil and have it pinned to the chassis.
my 2 cents |
|
|
| Saurav |
Arnold, I think that's what I'll do to begin with.
I set up the power transformer today, wire-nutted all secondary wires, and tested my OPT with the scope on the primary leads. I got a lot of noise, and finally ended up shorting the OPT outputs, and grounding one of the inputs (the one the probe's ground was connected to). Then I got a consistent reading, and could see the effects of changing transformer orientation. And this is where things got strange. I got the smallest waveform on the scope if the OPT's laminations were oriented the same way as the power transformer's laminations. That's the opposite of everything I've ever read. The waveform also changed shape. It was never a sine wave, it was more like a double triangle/sawtooth kind of a wave.
Since I'm such a smart guy, I had drilled all the holes for the OPTs before I tested this :) That's not a biggie though, the holes can be covered and new holes can be drilled. However, I don't understand why the lowest induced noise happened when the laminations of the two transformers were lined up. Are the coils wound differently in the two? I connected one of the 2A3 filament transformers too, just to make sure that that didn't change things. No current was being drawn from either transformer though, and I don't know how much of a difference that will make to radiated electromagnetic fields. I know the heater wires themselves will radiate noise once they're carrying current. And the PS choke isn't connected either, I don't know if that can have as much of an effect as the PS transformer.
Should I wait and build the whole circuit with clip leads and then test for OPT position? I don't know how much hum I'm getting either, my scope has a gain control with no marking s on it, and several stickers saying it's uncalibrated. I should get hold of a reliable signal generator and calibrate my scope. Anyway, it looks like I have anywhere from 5mV to 8mV of hum. If I don't ground the probe lead, that becomes 50mV of very noisy hum.
If anyone can put all of this together and derive any insights from it, that would be really helpful.
Thanks,
Saurav |
|
|
| dhaen |
Saurav,
| quote: | | And the PS choke isn't connected either, I don't know if that can have as much of an effect as the PS transformer. |
Two things to say about the choke placement:
The choke can recieve field from the mains transformer. With full wave or bridge rectification, this is always destructive to performance. It's got to be be very close and in-line for this to happen.
The choke can transmit field to the audio transformers. This is usually destructive, but can sometimes be constructive, and reduce other hum.
Bottom line: Bolt down the choke last.
Cheers, |
|
|
| EC8010 |
Shorting the OPT outputs will definitely produce odd results! Perhaps you need to earth the chassis of the output transformer and the mains transformer. When you do this test, you should see a nice clean sine wave, with maximum amplitude when the coils are aligned, and far less at the null.
Your oscilloscope sounds very strange. It doesn't need to be calibrated, all you're looking for is a minimum. |
|
|
| Saurav |
I was thinking about this last night, and I think I know what might have happened. When I connected the IEC power socket, I only used the hot and cold terminals and hooked up the PS trafo to those, I did not connect the earth terminal to the chassis. So, my aluminum chassis was floating, and so were the frames of the transformers sitting on it. By connecting the probe ground clip to the chassis (and one of the OPT's leads), what I did was ground my chassis, and the transformers sitting on the chassis, which probably helped clean up the signal.
| quote: | | When you do this test, you should see a nice clean sine wave, with maximum amplitude when the coils are aligned, and far less at the null. |
Potentially dumb question - are the coils aligned when the laminations are aligned? Or can coils be wound/oriented differently w.r.t. the laminations?
I'll try it again with the OPT outputs unshorted. I definitely did not get a sine wave. I got a triangular wave with one large triangle and one small triangle, which changed shape and amplitude as I turned the OPT.
And my power transformer is humming. I can't feel it vibrating when I touch it, but I can hear it. It'll probably get worse once I start drawing current through it, right? I'll probably go ahead and mount it on grommets and use a ring connector to earth it.
| quote: | | Your oscilloscope sounds very strange. |
It's a Tek (forget the model #) 100MHz scope that I picked up for $75 from a local surplus store. 1 timebase unit and 2 dual channel amplifiers included. Pretty good deal, I thought :)
| quote: | | It doesn't need to be calibrated, all you're looking for is a minimum. |
That's what I figured when I bought it.
John,
Thanks for the advice. I'll keep an eye on the choke's effects.
Since it's all 60Hz, can the hum balance pot be adjusted to cancel out electromagnetically induced hum? I know it's meant to balance the filament transformer to be symmetrical around ground, but can it be used after everything's been put together to just minimise the final hum from all sources? I know that's a bandaid, but I'm just wondering if it'll have any effect. |
|
|
| EC8010 |
Coils are not necessarily aligned when laminations are aligned. One coil could be pointing horizontally, and the other vertically (like your output transformers). You should get quite a large signal coupled from a mains transformer into an output transformer when the coils are aligned, perhaps even a volt.
The Tek sounds like a 7000 series. They had very nice tubes with excellent focus. Don't worry about "uncalibrated" labels on oscilloscopes. Oscilloscopes aren't really for measuring, they're for looking at shapes. Try looking your 'scope up on the web. Old Teks are very popular with engineers, some people even collect them! |
|
|
| dhaen |
| quote: | Originally posted by Saurav
snip...
Potentially dumb question - are the coils aligned when the laminations are aligned? Or can coils be wound/oriented differently w.r.t. the laminations?
John,
Thanks for the advice. I'll keep an eye on the choke's effects.
Since it's all 60Hz, can the hum balance pot be adjusted to cancel out electromagnetically induced hum? I know it's meant to balance the filament transformer to be symmetrical around ground, but can it be used after everything's been put together to just minimise the final hum from all sources? I know that's a bandaid, but I'm just wondering if it'll have any effect. |
No, the transformer field is 60Hz with some 2nd and 3rd harmonics, and HF caused by rectifier switching. The choke field is 120Hz, and not sinusoidal. The heater hum is 120Hz, and roughly sinusoidal.
There are 3 possible field planes.
Cheers, |
|
|
| Saurav |
Why would the heater be 120Hz? It's direct AC from the filament transformer, not rectified. Or does the fact that it's "center tapped" through the cathode bias resistor make it 120Hz? I understand that the choke field is 120Hz.
| quote: | | You should get quite a large signal coupled from a mains transformer into an output transformer when the coils are aligned, perhaps even a volt. |
So that would be if I laid the OPT on its side? I'll try that, at least that way I'll have some idea that I'm on the right track :)
| quote: | | Try looking your 'scope up on the web. |
I did, and I think I looked up user manuals for the plugin modules on it too. I just don't remember the model number off the top of my head. |
|
|
| dhaen |
| quote: | Originally posted by Saurav
Why would the heater be 120Hz? It's direct AC from the filament transformer, not rectified. Or does the fact that it's "center tapped" through the cathode bias resistor make it 120Hz? I understand that the choke field is 120Hz.
So that would be if I laid the OPT on its side? I'll try that, at least that way I'll have some idea that I'm on the right track :)
I did, and I think I looked up user manuals for the plugin modules on it too. I just don't remember the model number off the top of my head. |
I should have made clear that the hum pot will null out 60Hz, but there are 120 heating cycles per second. That's where my 120Hz comes in, and that's what you'll have left.
WRT orientation: Most stand-up output and mains transformers are wound so that the windings go up and over. that means they can be orientated at 90 deg just by turning one 90deg, looking from the top. It is then possible to orientate the choke so that it's windings are circular, looking from the top. Thus you can have 3 planes.
A very difficult concept to put into words (for me anyway:rolleyes:) )
Cheers, |
|
|
| EC8010 |
| quote: | Originally posted by Saurav
Why would the heater be 120Hz? It's direct AC from the filament transformer, not rectified. |
The hum comes from the changing AC being partly tracked by the temperature of the filament. Heat doesn't know about positive and negative half-cycles, it just responds to peaks, so it effectively rectifies the AC. (More technically, P = V squared over R, and cos(2A) = 2cos squared(A) -1)
Edit: Calling Planet 10. Is there any way of writing equations so that they make sense? |
|
|
| Saurav |
| Ah. That makes sense. Thanks. |
|
|
| dhaen |
EC8010,
Why not write it out in whatever program you have, and then use a screen area capture prog to make a .gif file. You can then attach it as a picture.
I think we are severely limited in the html world, in terms of what can be transmitted. It would take some Java or suchlike to actually generate it locally.
Cheers, |
|
|
| EC8010 |
| quote: | Originally posted by dhaen
Why not write it out in whatever program you have, and then use a screen area capture prog to make a .gif file. You can then attach it as a picture. |
Sounds like a good ploy. |
|
|
| Saurav |
Doing OK so far...
I liked the copper and black look of PassFan's amp, so I decided to try some copper metallic paint. This is definitely my weakest area, painting metal. I always get blotches on there with spray paint, and sometimes the paint doesn't stick. You can kinda tell from these pictures, the paint's "peeled" off in a few places, and it's pretty uneven. Maybe I'm using the wrong kind of primer, I don't know.
Anyway... I'll probably start on the wiring tomorrow, and maybe take pictures of the underside. |
|
|
| arnoldc |
| whoa! what happened to the 125ESE? :eek: don't you have a source for end bells? sorry, it's just me... :dead: |
|
|
| Saurav |
| Yeah, I decided to just not bother with taking the transformers apart to add bell ends. I thought about putting the 125ESE's under the hood, but it's getting a little crowded in there already. |
|
|
| Morse |
Hi Saurav;
That amp's shaping up fine!
>>>...This is definitely my weakest area, painting metal. I always get blotches on there with spray paint, and sometimes the paint doesn't stick...<<<
One question about the 'sticking problem': did you clean and thoroughly degrease the metal before priming? If not, on your next project you might try something like acetone - and DO NOT touch the chassis with your hands after cleaning it (wear clean gloves or handle the chassis only from the underside). Oils from your skin can cause all sorts of problems with finishes....
The best way I've found to get a good paint finish is to work with several thin coats rather than a single thick one. As far as the blotches are concerned, you can GENTLY sand them down smooth and repaint over top of them. Start with a 400 grit for big nasty runs or brush marks in the paint, 600 grit as the second step, and 1500 grit for the final finishing. During the later steps, you should be very VERY gentle with the sanding. You can get 600 and 1500 grit papers at any auto shop. After you've got a mirror gloss going for you, you can apply a transparent topcoat to help protect the finish.
Good luck and all the best,
Morse |
|
|
| Tom Bavis |
| Just looked at your chassis picture, and I'm wondering if those ceramic 4-pin sockets have any clearance under the chassis. The rivets are connected to the terminals, and you want 1/8" (or an insulator) berween them and the chassis. |
|
|
| Saurav |
| quote: | | did you clean and thoroughly degrease the metal before priming? |
Yup. I'd tried vinegar in the past without much success, so this time I actually bought "metal etch". The primer's bonded to the metal fine, when the paint peels off I see primer underneath. Maybe I have the wrong kind of primer.
Next time I'll try sanding. I wasn't sure if I could do that.
| quote: | | The rivets are connected to the terminals, and you want 1/8" (or an insulator) berween them and the chassis. |
The rivets are a little countersunk though, and are below the surface of the ceramic. Probably not 1/8" though. In any case, I'll double check, thanks for the warning. What kind of insulator could I use? It would have to handle fairly high temperatures, I would think? |
|
|
| Saurav |
Well, I didn't post this last night. I completed it, nothing blew up or caught on fire, and it sounds fabulous. It's the old "I'm hearing things I never heard before" cliche. The music sounds smooth and relaxed, with the little details being more easily audible that before.
I still need to fix a few things. I totally miscalculated the amount of current the 6SL7s would draw, so the B+ on the driver tubes is way too high, I need to buy larger value resistors today. And the wiring's somewhat messy because I decided to leave all transformer leads at their original lengths. I managed to tuck everything away near the rear of the chassis where the PS is, so I hope that won't affect the sound too much. It sounds pretty quiet with just an adjustment of the hum pots. With 97dB speakers, I can barely hear the hum 2' away.
Thanks for all the help, everyone. |
|
|
| Morse |
Hi Saurav!
Great!! Glad to read that your amp's working well and that you're happy!! Isn't it a magical moment, when your creation starts to produce music for the first time? It's addicting though, so you'll soon start thinking of building another - maybe a litlle one for the den or the office..... ;-)
>>>...The primer's bonded to the metal fine, when the paint peels off I see primer underneath. Maybe I have the wrong kind of primer...<<<
Hmmmm, you've got me stumped. I've had troubles in the past with getting things to stick to the metal but not the primer. What kind of paint did you use? I usually use auto body type enamels, though some of my friends who used to build telescopes swear by epoxy paints (they'd use 'em on the tubes and mounts, which can get scraped, etc in handling).
Good luck with your amp and all your projects!!
All the best,
Morse |
|
|
| Saurav |
| Rust-Oleum Metallic Copper, and as far as I remember the primer was Rust-Oleum too. I'm not sure what medium the paint is. |
|
|
| Saurav |
OK, more questions.
How hot should a 10W sandcast resistor get? I put in a pair of 100 ohm 10W resistors in series between the rectifier and the first filter cap/choke, to drop the B+ voltage a bit. Here's my calculation:
RMS current draw from rectifier: ~ 120 - 150mA. Figure 60mA for both 2A3s, about 1.5mA for each 6SL7, 150mA is a good highish figure. For each 100 ohm resistor, that's an RMS power dissipation of 1.5 - 2.5W per resistor. Now these resistors aren't seeing the RMS current draw, they're seeing the current surges as the cap charges during the duty cycle. If I assume a duty cycle of 0.1, that's 1.5A surges, which puts me at 225W dissipation.
Now 225W doesn't seem like a reasonable value to use for the required power rating in this position. Is 10W enough, or should I get higher rated resistors? I ran the amp for a minute or so to measure bias voltages, and these resistors got hot enough that I wouldn't want to touch them for more than a couple of seconds. And based on my voltage measurements, my estimates for the current draw are fairly close.
Or should I re-model the PSU with a lower valued initial cap? Won't adding dropping resistors increase the output impedance of the power supply, and cause it to sag more on transients?
Thanks in advance,
Saurav |
|
|
| Saurav |
And pictures:
That's a red lamp shining on the amp, not its natural color. I added a .022 cap from the input RCA to the grid of the first 6SL7 to roll off the bass going to the 2A3s, 125ESEs and most importantly my speakers. You can also see the extra 125ESE leads just tie-wrapped together in the middle. Any advice about a better way to handle these wires would be appreciated. However, my biggest worry right now are the PS dropping resistors that I mentioned in the previous post.
Thanks,
Saurav |
|
|
| Saurav |
| One more question. Pin 1 on a 5AR4 is usually shown as a dotted line, with N.C/I.C. written on it. I assume that means not connected or internall connected. However, there are other pin positions that aren't used on this tube (and the pins aren't even present), so what is special about pin 1? Is it a shield that I'm supposed to connect to ground? Or should I just ignore it? |
|
|
| EC8010 |
| N.C. or I.C. translates as "don't connect to this pin!" Often, it's a wire going up to help support a heavy structure like an anode, but it can vary between manufacturers, so one valve might use the pin and another not use it. |
|
|
| Saurav |
| Thanks. Could you please help me out with my question regarding B+ dropping resistors? It's about 6 posts up from here :) I think I made 4 posts in a row to this thread. |
|
|
| JOE DIRT® |
I`m not an expert on valve amps but I think if your using a resistor to drop your voltage then that 10 watt resistor is being overworked a wee bit from what you have said....there are more experienced members here with tube audio p/s`s that can assist you further...just be patiant;)
DIRT® |
|
|
| EC8010 |
Those resistors will get hot, which is fine for them, but not so good for anything nearby.
If you are using PSUD for modelling your power supply, you will find that it can give an RMS current (in the table on LHS) for this resistor which you can use for your heating calculation. I doubt if you are disspiating more than 2.5W, but where is the heat going to go? When you use your amplifier, the resistor is enclosed by the chassis and there isn't a free flow of air, so it heats up the internal air until the air heats the chassis, which can then lose heat to the surrounding air. I see you've used metal-clad resistors bolted down to the chassis elsewhere, I'd use some more for the 100R. (And don't forget a thin smear of heatsink compound before fitting the resistor.) |
|
|
| Saurav |
Joe,
Thanks for the encouragement. I took the resistors out for tonight. I figured I'm better off running my tubes a little hot and shortening their life a little, than having my amp catch on fire :)
EC8010,
I thought that with resistors placed before the first filter cap, RMS current didn't apply because the current through the resistor is in pulses, not a steady draw?
The metal-clad resistors are for the 2A3's cathode bias. I saw some that looked like that at the surplus store today, I'll go back there tomorrow and see if I can find something suitable. The heatsink compound is a good idea.
In general, is it better to lower B+ by changing capacitor values? Seems to me that adding resistors would make the PS output voltage sag more during high current demand. Or is that not an issue with a class A SE amp? |
|
|
| EC8010 |
RMS current always applies - it's just that it's usually hard to calculate, and expensive to measure (have a look at the price of proper true-RMS meters). RMS is an equivalent DC current that has the same heating effect as any pulse or AC waveform.
SE amplifiers are more critical of their power supply than PP. Ideally, they would like a regulated HT. Either series resistors or tweaking reservoir capacitor value allow you to drop HT volts. Tweaking reservoir value is slightly better because it doesn't waste power (increasing heat within the chassis). Both methods make the power supply sag more under load. |
|
|
| dhaen |
RMS:
As EC8010 says, RMS always applies. It's the area under the graph line that determines it. The 0.707*peak rule only works for sine-waves, hence his recommendation to use PSUD to do the work for you.
Placement of hot resistors:
Remember that the normal power rating (w) is only usable at or just above ambient. Put them in a hot chassis and they must be de-rated. See attached picture from:
http://www.irctt.com/pdf_files/PWRL.pdf
Keep them away from electrolytics and other heat sensitive components. |
|
|
| Saurav |
OK, I think I understand now. I can't just add up the RMS currents of the tubes to get the RMS current through the PS resistor, or use RMS equations that apply to sine waves. But PSUD will calculate the RMS current for me, so I can use that value for the power calculations. And PSUD says the RMS current is ~ 200mA, which is more than (2x60 + a little bit), so that makes sense now.
| quote: | | Both methods make the power supply sag more under load. |
Didn't know that.
Thanks a lot, this is a lot clearer to me now. |
|
|
| dhaen |
It is true that SE is power supply critical, this being because the power supply is in series with the output signal. But being class A, the current average demand does not theoretically change with signal. This is true only as long as the stage introduces no distortion. So in practice it means that there is hardly any change at normal signal levels, but a significant change when clipping is reached.
If you do not have access to a distortion meter, you can actually use the voltage change to determine the distortion.
BTW Nice work so far ;) |
|
|
| Saurav |
| quote: | | BTW Nice work so far ;) |
Does the winking smiley mean I've actually done a really shoddy job? :)
Thanks for all the help. I'll go buy some more parts today, a lower valued capacitor and some high powered bolt-on resistors if I can find them in the right values. |
|
|
| dhaen |
| quote: | Originally posted by Saurav
Does the winking smiley mean I've actually done a really shoddy job? :)
snip.. |
Hell no! There are a lot of us who've had more experience, and don't turn out something as good.
| quote: | Originally posted by Saurav
snip..
Thanks for all the help. I'll go buy some more parts today, a lower valued capacitor and some high powered bolt-on resistors if I can find them in the right values. |
You're welcome :) (careful with the smile)
Now: How does it sound?
Cheers, |
|
|
| Saurav |
Thank you for the kind words. The amp sounds beautiful. Effortless, relaxed, smooth. Compared to my earlier amps (ASL Waves, *excellent* amps for $200, but nevertheless, there's only so much you can do with $200), sounds decay for much longer, where earlier they'd get lost in the hash. I think this amp handles overload situations better too, because on old vinyl, the music seems to be "visible" through the surface noise much better than before. I haven't yet tried any complex/congested music, that's one area where the ASL Waves were a little weak and I expect this amp to be a lot better.
It took me a little while to relax about the 6SL7's plate voltage being 330 where it should have been 300, and more importantly, it's cathode-heater voltage being 94 where the max allowed is 90. It's hard to set the voltage divider for the 6SL7's heater when my B+ is going all over the place with the changes I was making. Once I've sorted my B+ out, it'll be easier to pick resistor values to get the heater at the potential I want. I figured the 6SL7s would survive for a night or two with the heater-cathode voltage being 4% over spec.
You really don't know what your speakers are capable of until you drive them with a good amp. |
|
|
| EC8010 |
| Glad to hear it sounds good. What next?:) |
|
|
| Saurav |
| LOL! Listening to music, at least for a few days, hopefully, before I start getting itchy again :) |
|
|
| Saurav |
OK, I think this should do it:
My current PSU has a 4.7uF cap in the first position, and both voltages are about 20V too high. I found a 3uF 450V myar cap at the surplus store (Aerovox, is anyone familiar with that name?) It was interesting to see Sprague/Wima MKP caps, Dale resistors etc., looking a little dusty and priced quite a bit lower than online dealers.
You can't see it in the scan, but the peak voltage on C1 is 438 and RMS is 345, so I think a 450V cap should be OK here. I spent a long time looking for 600V caps in the 2-3uF range but couldn't find any. I then remembered that the only time I'd seen the voltage go up above 400V was when I had only the 5AR4 in the circuit, so I think this should be fine. Not 100% idiot proof, but I'm sure there are other areas in this amp where an inexperienced user could cause damage. |
|
|
| EC8010 |
| BHC Aerovox is a British manufacturer, they're on the web. Capacitors care about peak voltages, but RMS currents. You need to find out the Equivalent Series Resistance (ESR) of your capacitors (the manufacturers give values at 120Hz), and compare the reservoir capacitor's ripple current rating to the RMS current predicted by PSUD. You can then replace the 2R default values in PSUD, and if you have not already done so, use accurate values for the transformer winding resistance. You need to be very careful with simulations, they're quite useful, IF they are given accurate data... |
|
|
| Saurav |
| quote: | | and if you have not already done so, use accurate values for the transformer winding resistance |
I should have done that before I wired everything up, I realized that yesterday. I should be able to get a proper reading with the rectifier out of the circuit though, the CT to ground shouldn't make a difference to the resistance seen by the DMM. I measured the choke's DCR and updated my model with it. I'll look up the capacitor's ESR.
| quote: | | You need to be very careful with simulations, they're quite useful, IF they are given accurate data... |
That's good advice.
| quote: | | BHC Aerovox is a British manufacturer, they're on the web. |
I found discussions about their motor run caps. They seem to be a pretty decent quality manufacturer, based on the opinions I read. |
|
|
| Saurav |
Hmm. Here's what the cap says:
Aerovox
AFPS 3 uF
K/450 VDC
Assembled in Mexico
It has 00-48 along one edge. The cap is a 1" long plasticy cylinder with an oval cross-section. Both ends are a blue plasticky material. One lead comes out the center of the oval end face, the other lead runs along the outer surface of the cylinder (I can see the lead under the wrapped cover with the lettering). This lead also has a green line marked in by hand over it.
I can't find an AFPS series on their website. Does the green line mean that's the side which goes to ground? Since that lead's on the outside, I would assume that's what it means?
It kinda looks like the middle cap in the top row here, except the ends are blue:
Looking through the tables, all the 3uF caps here have similar ESR and ripple current ratings, so I'll use these. Does anyone have any idea what the green line means?
Here's the HTML catalog: http://www.aerovox.com/catalogs/arpt_afpt/index.htm |
|
|
| EC8010 |
| The green line means "outer foil" and should be connected to the lowest impedance to ground. That means that if you are using it as a coupling capacitor, the foil goes to the output of the preceding stage. |
|
|
| Saurav |
| Thanks. That's what I thought it meant, but it's better to check than make assumptions :) Reading Morgan Jones' book helped me to understand a lot of stuff I always read about caps but didn't understand the reasons behind. |
|
|
| Morse |
Hi Saurav;
Your amp is really looking good!
Just a couple comments, while I'm waiting for the paint to dry on a CD stand that's under construction:
1. I really wouldn't get TOO hot and bothered if a 10w wirewound resistor dissipating 2 watts gets hot. That's normal. OTOH, it's best to keep things cool for the longest lifespan on the other components in the amp (particularly electrolytic caps and and carbon comp resistors) so switching to heat sinked metal finned resistors would be a good move. EC8010 definitely gave you some worthwhile advice there!
2. Valves are pretty darn tough customers! A little extra voltage won't necessarily hurt anything, unlike SS equipment. I'd be more concerned about an excess of overall plate dissipation than a little extra voltage (particularly if it's not arcing or otherwise misbehaving). Even so, I've been known to allow an extra tenth of a watt dissipation on output valves without losing sleep. To each his own....
3. If you really want to get a 'lotta bang for the buck' improvement (literally), you could put a .1uF "X" class 250VAC UL Listed safety cap** in as a mains RF filter. My 2A3 improved surprisingly with such a tiny little tweak - enough so that I now have it as a standard feature on all my amps.
4. For the best air circulation, you ought to put some sort of feet under your amp's chassis so that air can flow up from beneath. In conjunction with a few strategically placed vents, it's a cheap way to help cool things down.
Enjoy your amp!! :-)
All the best,
Morse
**For the record, under no circumstances should a non-"X" rated safety cap ever be used in a mains filter - any other capacitor type is a potential fire hazard in this application. Personally I have had excellent results with Panasonic X2 caps that are designed specifically as interference filters. They're about a buck apiece from Digikey. |
|
|
| Saurav |
| quote: | | 3. If you really want to get a 'lotta bang for the buck' improvement (literally), you could put a .1uF "X" class 250VAC UL Listed safety cap** in as a mains RF filter. |
Done that already. I had one left over from a previous project when I ordered 2 of everything, forgetting that the power supply parts list was common to both channels.
| quote: | | For the best air circulation, you ought to put some sort of feet under your amp's chassis so that air can flow up from beneath. In conjunction with a few strategically placed vents, it's a cheap way to help cool things down. |
Done that already too :) Though the feet aren't very big, because there's only so much contact area for the glue to hold on.
I got a lower valued filter cap, and that's brought my B+ down to something that I think will be fine. I picked up a couple of 100 ohm 40W resistors too, I might throw one of those in there. They're not as nice as the cathode bias resistors I have in my amp, but they do bolt on to the chassis, and it looks like the metal will help dissipate heat.
| quote: | | I'd be more concerned about an excess of overall plate dissipation than a little extra voltage |
That's good advice. I'll probably write down all my voltage measurements tonight and do the calculations. So far I was just trying to get them close to the values in the schematic. |
|
|
| fdegrove |
Hi,
| quote: | | **For the record, under no circumstances should a non-"X" rated safety cap ever be used in a mains filter - any other capacitor type is a potential fire hazard in this application. Personally I have had excellent results with Panasonic X2 caps that are designed specifically as interference filters. |
Actually, while I fully understand your warning, you can use any filmcap as long as you're aware that X-class caps are rated for AC voltage service and other filmcaps such as coupling caps are rated for their DC blocking service.
So, generally speaking a 600VDC rated cap shouldn't have any trouble working at 115/240 VAC.
What you have to be aware of though is that some, not all, X-rated caps sometimes contain a resistor as well, which make them more ideal for snubber service at the primary side of a xformer or across rectifier diodes for instance.
Cheers,;) |
|
|
| Morse |
Hi Frank;
Sorry about making my posts look like the boiler plate on the bottom of a contract, but we live in a litigious society and I just like to play it safe!! ;)
One thing to add is that I always put my "X" caps after the fuses. That way if they do fail catastrophically, I've got something to "catch" it.
Anyway, my understanding is that "X" caps are designed to take powerline spikes without failing, and when they do fail, to fail open rather than closed. Also, the small supply of 'em I have over here are all potted in fire retardent materials. They're really pretty imposing things!
Personally I would spend the $1 or so on the 'real deal' and not worry, but to each his own!!
All the best,
Morse |
|
|
| fdegrove |
Hi Morse,
| quote: | | Sorry about making my posts look like the boiler plate on the bottom of a contract, but we live in a litigious society and I just like to play it safe!! |
No problem.It is always best to use the appropiate part for the task at hand.
No arguing there.
Same to you,:cool: |
|
|
| dhaen |
Whilst I welcome you back Frank, I must take issue with your suggestion of using non x-rated and y-rated caps in mains filters.
These certified components are manufactured specially for this purpose, and have special features. A few are:
A guaranteed max leakage
Self healing
Max value
Flamability and gas safeguards
But most importantly, they are subject to a strict QC.
Whilst other caps may be as good, there is no guarantee and no certification.
Cheers, |
|
|
| fdegrove |
Hi,
Thank you for the welcome back.
I'm certainly not going to argue about the obvious.
Surely, I wouldn't spread this old fox trick through the forum so, let's just disregard it and stick to the appropriate parts as I suggested.
| quote: | | Whilst other caps may be as good, there is no guarantee and no certification. |
Fair enough, I suppose it's only reasonable to assume that you know what you're doing...so, do I but it would be unfair to assume the same of all the pundits...
No big deal,;) |
|
|
| Positron |
Morse, maybe I am too late. I was going to mention I found a body painting private shop, locally, who does professional baked on (I forget what you call it now) for cheap, like $25.00.
My painter does race cars for the local Peoria racers. If you are still looking, I found mine by going to the paint shops and asking around.
Hope this helps Morse.
Steve |
|
|
| fdegrove |
Hi,
Steve, you're one helluva fellow.;)
Here's what I do if I feel that I can't get professional results by doing it myself:
I call upon a garage that has a bodywork spray cabin and tell them the paint has to withstand high temperature and has to be scratchproof.
Upon which they usually suggest an epoxy powder coating which does all of the above.
Cheers,;) |
|
|
|
|
