I have a 1960s Ace Tone Elite (a Japanese company, precursor to Roland Corp.) amplifier that I've had for a while. It worked generally well. The reverb tank was physically defective and no longer worked and the tremolo was flakey. Sometimes it would work and sometimes it wouldn't.
So my question is: What's the best way to fire this up? Tubes out and test voltages?
I'm pretty confident in the soldering work I did. I can tell when I do a sketchy job soldering and I did about the best soldering work I've ever done with this. Everything actually went surprisingly well (including pulling out the baffling, unstapling and restapling the grill cloth, to replace the speaker). I expected a bunch of hiccups, but so far everything has gone perfectly, so I don't want to plug it in and have it all go to hell...
- I replaced the reverb tank with one recommended by Enzo (based on the reverb circuit).
- I replaced all the caps except for the can capacitor (I can't find an equivalent that will fit in the space. But as it seemed to work okay before the repair work, I was inclined to just leave it.) and one other small one (it was wired point to point on the other side of the board from the others and I simply missed it when I was looking at what I needed to order).
- In the process of replacing the reverb tank one of the wires to the output transformer got disconnected and I decided to replace both the speaker and output transformer in the hopes of just a better sound overall, as the speaker was pretty weak).
So my question is: What's the best way to fire this up? Tubes out and test voltages?
I'm pretty confident in the soldering work I did. I can tell when I do a sketchy job soldering and I did about the best soldering work I've ever done with this. Everything actually went surprisingly well (including pulling out the baffling, unstapling and restapling the grill cloth, to replace the speaker). I expected a bunch of hiccups, but so far everything has gone perfectly, so I don't want to plug it in and have it all go to hell...
I've got everything hooked up and ready to go, but waiting on some advice here on how to move forward.
For building amps, it seems, from my readings on the forums, that people normally power on the first time with the tubes out so that they can verify the voltages on the various tubes before actually putting the tubes in. I don't know that I need to do this. The only real concern I might have is if I've created a short when soldering, but as I said, this is one of my better soldering jobs, and I don't think I've done that. It's also a pretty spacious PCB with lots of space between traces, so it'd be hard to create a non-obvious short.
And, worst case, I have the original tubes. I could fire it up with those and if one or more blows, I'd still have the new ones as backup.
My other concern is that a short might cause the can cap to blow (which if it didn't injure me, might give me a heart attack).
Anyway, I'd appreciate some advice on my next step.
For building amps, it seems, from my readings on the forums, that people normally power on the first time with the tubes out so that they can verify the voltages on the various tubes before actually putting the tubes in. I don't know that I need to do this. The only real concern I might have is if I've created a short when soldering, but as I said, this is one of my better soldering jobs, and I don't think I've done that. It's also a pretty spacious PCB with lots of space between traces, so it'd be hard to create a non-obvious short.
And, worst case, I have the original tubes. I could fire it up with those and if one or more blows, I'd still have the new ones as backup.
My other concern is that a short might cause the can cap to blow (which if it didn't injure me, might give me a heart attack).
Anyway, I'd appreciate some advice on my next step.
I'm not really a tube guy, so take the following with a large grain of salt. First, I'm not sure that tubes-out measurements will tell you a lot, since without the tubes very little current is flowing, hence no voltage drop across resistors. About all it will tell you is whether the PS voltage is in the right ball park.
Second: use a dim-bulb tester! Wire an incandescent light bulb (power rating considerably higher than the quiescent power consumption of the amp) in series with the AC power. When you power up the amp the bulb should glow brightly for a brief period (like a second or two) then settle down to a dim glow. If it glows brightly it tells you two things: 1 something is shorted or blown and 2 the light bulb just saved you a lot of heartbreak!
Second: use a dim-bulb tester! Wire an incandescent light bulb (power rating considerably higher than the quiescent power consumption of the amp) in series with the AC power. When you power up the amp the bulb should glow brightly for a brief period (like a second or two) then settle down to a dim glow. If it glows brightly it tells you two things: 1 something is shorted or blown and 2 the light bulb just saved you a lot of heartbreak!
Can caps that age should be replaced. They can actually short and take other things with them.
Perhaps you could post a couple pictures of this cap for further advice. There ARE a lot of can caps still available new.
It is also not unheard of to use several individual caps in place of the can cap.
Power Up.
Google Light Bulb Limiter;
If you are pulling excessive current or have a short, it is a simple way to detect it.
Perhaps you could post a couple pictures of this cap for further advice. There ARE a lot of can caps still available new.
It is also not unheard of to use several individual caps in place of the can cap.
Power Up.
Google Light Bulb Limiter;
If you are pulling excessive current or have a short, it is a simple way to detect it.
Thanks. I'll do the incandescent light bulb thing. The trick is going to be to find one. I'm sure we have one somewhere (we recently switch to LEDs all over the house, but I'm sure we kept the old ones somewhere).
WRT the can cap, I plan on replacing it, but it's been working fine for the last year and a half or so that I've had the amp. I just assumed it'd be okay until I find a replacement that will fit the spot.
It's a 2 part 40/40MFD 350V can and it's 1 1/8" in diameter. Most of the can caps I've seen that would make a good replacement are at least 1 3/8: in diameter and I'm concerned the connectors may come into contact with the chassis where the connectors come through (it's a hole slightly smaller than the diameter of the capacitor itself). I'd rather not buy one without knowing it's going to fit.
Of course, I could get two 47uF caps that would be much cheaper and far smaller that I could cable tie together and figure some way to secure to the chassis in place of the giant can cap. Maybe I should just go ahead and do that. It'd be a shame to blow the can and damage other stuff that I've already replaced.
Here's the pic
I haven't finished securing the reverb wires and the wires to the OT. The resistors that are standing up were put there by my wife's uncle (he replaced some of the originals that had strayed from their proper values and put them in like that so I'd know which were original and which were his.) I separated those two that look really close (they weren't quite as close as they appear in the picture).
The original OT was secured to the speaker itself. The new one is attached to the inside of the cabinet. And yes, that's authentic wallpaper used in place of something cheap like tolex.
WRT the can cap, I plan on replacing it, but it's been working fine for the last year and a half or so that I've had the amp. I just assumed it'd be okay until I find a replacement that will fit the spot.
It's a 2 part 40/40MFD 350V can and it's 1 1/8" in diameter. Most of the can caps I've seen that would make a good replacement are at least 1 3/8: in diameter and I'm concerned the connectors may come into contact with the chassis where the connectors come through (it's a hole slightly smaller than the diameter of the capacitor itself). I'd rather not buy one without knowing it's going to fit.
Of course, I could get two 47uF caps that would be much cheaper and far smaller that I could cable tie together and figure some way to secure to the chassis in place of the giant can cap. Maybe I should just go ahead and do that. It'd be a shame to blow the can and damage other stuff that I've already replaced.
Here's the pic
I haven't finished securing the reverb wires and the wires to the OT. The resistors that are standing up were put there by my wife's uncle (he replaced some of the originals that had strayed from their proper values and put them in like that so I'd know which were original and which were his.) I separated those two that look really close (they weren't quite as close as they appear in the picture).
The original OT was secured to the speaker itself. The new one is attached to the inside of the cabinet. And yes, that's authentic wallpaper used in place of something cheap like tolex.
One reason for powering up with no tubes is to make sure you have bias voltage present if fixed bias is used. Don't want any B+ without bias present. Bring it up slowly either with a current limiting light bulb or a variac.
Variacs are better because you can have circuit voltages present when only 50-60 VAC present on primary and add voltage slowly. It will help you catch problems before they are at high voltages and will help form new filter caps slowly if they were added.
Variacs are better because you can have circuit voltages present when only 50-60 VAC present on primary and add voltage slowly. It will help you catch problems before they are at high voltages and will help form new filter caps slowly if they were added.
I replace tall can caps with a cinch type solder terminal strip and radial lead caps. these can go under the chassis on a machine screw. The radial lead caps are small enough to be supported by the leads. You could use 39 uf or 47 uf 350 v rated caps. I like ones rated over 2000 hours service life, as I had to replace the can cap 4 times in the 44 years I've owned my hifi tube amp.
Cinch type terminal strips come from tubesandmore.com(AZ), triodeelectronics.com (IL) Electronicsurplus.com (NY) or now for a limited time, mcmelectronics.com (OH) The first two also sell short lengths of 600 v rated tin plate wire for running the high voltage to a different location without shorting out. I buy machine screws and elastic stop nuts from mcmaster.com in boxes of 50 or so, but you might be able to get #6 and regular nuts at a local hardware store (not a home store IMHO). If you use regular nuts, glue them down so they don't fall out when carrying the amp around.
Can cap replacement is the thing my tube amps need more than anything- both dynaco and hammond. I measure the voltage out on the speaker when the amp sounds "polite" usually to find the watts are way down from spec on the push pull chart of the tube datasheet. triodeelectronics gives away the tube datasheets, one reason to support them.
I form new filter caps with the ohms scale of the DVM, not in circuit. You can watch resistance climb as it goes. This is particularly important with caps that are past their "shelf life" which means they have become uninsulated on the shelf waiting for you to buy them, or in your parts bin waiting for you to use them. This is a different limit than the cracking of the sealant rubber due to oxygen, which is a reason I don't buy e-caps off e-bay: no telling how old they are.
Cinch type terminal strips come from tubesandmore.com(AZ), triodeelectronics.com (IL) Electronicsurplus.com (NY) or now for a limited time, mcmelectronics.com (OH) The first two also sell short lengths of 600 v rated tin plate wire for running the high voltage to a different location without shorting out. I buy machine screws and elastic stop nuts from mcmaster.com in boxes of 50 or so, but you might be able to get #6 and regular nuts at a local hardware store (not a home store IMHO). If you use regular nuts, glue them down so they don't fall out when carrying the amp around.
Can cap replacement is the thing my tube amps need more than anything- both dynaco and hammond. I measure the voltage out on the speaker when the amp sounds "polite" usually to find the watts are way down from spec on the push pull chart of the tube datasheet. triodeelectronics gives away the tube datasheets, one reason to support them.
I form new filter caps with the ohms scale of the DVM, not in circuit. You can watch resistance climb as it goes. This is particularly important with caps that are past their "shelf life" which means they have become uninsulated on the shelf waiting for you to buy them, or in your parts bin waiting for you to use them. This is a different limit than the cracking of the sealant rubber due to oxygen, which is a reason I don't buy e-caps off e-bay: no telling how old they are.
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I would also power up without tubes at first, not only to verify bias is present, but mainly to make sure I didn't make any mistakes that will blow fuses or cause damage. The voltage readings will be worthless. With no tubes, there will be no current draw on the B+ supply, and so no voltage drop. That means the maximum B+ voltage will appear everywhere. SO you cannot check for say 450v here and 300v there, because it will just be 450v everywhere. Once you know it won't blow up and bias is there, then install the tubes and watch carefully.
I also usually leave old can caps in place for looks, take the wires off, and replace the sections with individual caps mounted in the circuit. They can be installed wired directly to terminals in the circuit or indeed, I also sometimes mount a couple terminal strips in there as tie points for discrete caps.
I also usually leave old can caps in place for looks, take the wires off, and replace the sections with individual caps mounted in the circuit. They can be installed wired directly to terminals in the circuit or indeed, I also sometimes mount a couple terminal strips in there as tie points for discrete caps.
Got the light bulb socket and some 47uF caps on order. If I put the lightbulb on a dimmer would that act as a poor man's variac? I'll get a couple of terminal strips, actually. I want to use one between the circuit board and the OT so that I can fully remove the circuit board without desoldering the the connection to the OT (because the OT is attached to the cab, not the chassis).
I hate waiting, but I want to do this right!
Thanks to everyone for their help and insight.
I hate waiting, but I want to do this right!
Thanks to everyone for their help and insight.
Got a delivery from Electronic Goldmine today. I had ordered a bunch of stuff for the amp I'm going to build. Included in it were five 47uF, 450V caps (of which I only expect to need 2 or 3 for the amp I'm building). Totally forgot I had those in the order. So I guess I can go ahead and replace the can cap (though I probably won't get time tonight).
I'm going to replace those two 15V electrolytics as well, but one of them (the one that was very poorly point-to-point soldered on the back side of the board) got disconnected on one end when I wasn't being quite as gentle as I should have and I'm not exactly sure where it was attached (it's among 3 different pads). So I guess that's going to force me to finish working out the schematic for the amp so I can figure out where it was connected. That, I might get to, tonight.
I'm going to replace those two 15V electrolytics as well, but one of them (the one that was very poorly point-to-point soldered on the back side of the board) got disconnected on one end when I wasn't being quite as gentle as I should have and I'm not exactly sure where it was attached (it's among 3 different pads). So I guess that's going to force me to finish working out the schematic for the amp so I can figure out where it was connected. That, I might get to, tonight.
Finally got around to finishing up the repairs on this amp. Put it back together and ran it through my current limiter, seemed to be okay, but no sound. The power light comes on and the heaters light up, so it has power.
I recapped. I'm pretty sure the cap job is good. It's on a PCB with lots of space between traces. It'd be hard to mess it up.
I replaced the reverb tank. If the reverb tank wasn't working at all, I'd still be getting sound, right?
What I'm unsure about is that I replaced the speaker and output transformer. The original speaker was a pretty junky speaker and the output transformer was in rough shape as well. The amp is only about 4 watts, but I got a 15 watt speaker. Is that going to be a problem (I wanted it to be usable as a cab with the other amp heads I'm building which will be higher wattage).
What's a good starting point for testing?
I recapped. I'm pretty sure the cap job is good. It's on a PCB with lots of space between traces. It'd be hard to mess it up.
I replaced the reverb tank. If the reverb tank wasn't working at all, I'd still be getting sound, right?
What I'm unsure about is that I replaced the speaker and output transformer. The original speaker was a pretty junky speaker and the output transformer was in rough shape as well. The amp is only about 4 watts, but I got a 15 watt speaker. Is that going to be a problem (I wanted it to be usable as a cab with the other amp heads I'm building which will be higher wattage).
What's a good starting point for testing?
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Here's my current plan:
1> Wait for my wife and daughter to get back in case I electrocute myself, I'll need someone to watch and laugh.
2> Using my scope, strum the guitar string and then check the grid signals from pre-amp to power amp. (Don't have a function generator :-( )
3> Assuming the signal gets that far, check it at the OPT.
1> Wait for my wife and daughter to get back in case I electrocute myself, I'll need someone to watch and laugh.
2> Using my scope, strum the guitar string and then check the grid signals from pre-amp to power amp. (Don't have a function generator :-( )
3> Assuming the signal gets that far, check it at the OPT.
I would measure all voltages, plate, screen and bias for all tubes against what they should be WRT the B+ rail voltages. Make sure the rail itself is good and then the pin on the tube that is connected to that node of the rail to make sure the proper voltages are present at the tube itself.
Yes, you should still get sound even if your reverb circuit isn't working, except if somehow where the signal splits to go to the reverb circuit, the signal is shorted to ground. This could rob the whole amp of the preamp signal. Not too likely but possible. Try unplugging the reverb tank to see if this makes a difference.
Maybe I missed it but did you post a schematic? I just saw the pic you uploaded.
Yes, you should still get sound even if your reverb circuit isn't working, except if somehow where the signal splits to go to the reverb circuit, the signal is shorted to ground. This could rob the whole amp of the preamp signal. Not too likely but possible. Try unplugging the reverb tank to see if this makes a difference.
Maybe I missed it but did you post a schematic? I just saw the pic you uploaded.
Well, bummer. Looks like I was careless when wiring the jack to the output transformer and it shorted and blew the OPT. Now I need to track down where I got it, because it was a pretty inexpensive one, as I recall.
Tracked the signal from pre-amp to the 5K ohm side of the OPT and it looked pretty good, so looks like everything else is probably okay.
Oh well, guess I won't be testing this amp for a bit. Guess I'll focus on the Hammond while I'm waiting for a new OPT.
Tracked the signal from pre-amp to the 5K ohm side of the OPT and it looked pretty good, so looks like everything else is probably okay.
Oh well, guess I won't be testing this amp for a bit. Guess I'll focus on the Hammond while I'm waiting for a new OPT.
Do you have a DMM? Short the leads together on the lowest setting to see where "zero" is for your meter. Most DMMs will be around .3 ohms. If that is the case, then you might not have shorted your secondary.
I have a DMM that "zeroes" at .3 ohms and measured the secondary of a single ended 10 watt amp. It read 1.3 ohms, so the real impedance is only one ohm.
I have a DMM that "zeroes" at .3 ohms and measured the secondary of a single ended 10 watt amp. It read 1.3 ohms, so the real impedance is only one ohm.
It was 0.2. Cool. I'll give it a shot in the morning, then. I was afraid to hook it back up for fear that it might blow the speaker or something.
Got to work on the Hammond a bit today as well. Got the 1/4" guitar jack in, got the reverb jacks relocated. I might be able to fire it up tomorrow too. That would be awesome.
Got to work on the Hammond a bit today as well. Got the 1/4" guitar jack in, got the reverb jacks relocated. I might be able to fire it up tomorrow too. That would be awesome.
If your tranny is shorted, you won't lose a speaker because current will take the path of least resistance, so current will flow in the shorted secondary if it is indeed shorted. It's like having a 1 ohm resistor in parallel with an 8 ohm, almost all the current will flow through the 1 ohm resistor. But it it was shorted, it should read .2 ohms.
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