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Old 27th May 2008, 02:51 AM   #1
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Default Tubelab Simple SE Rectifier Problem?

Well, I finally got my Simple SE all hooked up. In order to test it out, I hooked it up in triode mode without feedback. When I first tried to turn it on, I blew the diodes in the rectifier. After doing a little bit of research, I found an existing thread from about nine months ago. Here's a link - the section is on the second page, about halfway down:

Edcor OPT's w/ SimpleSE

It turns out that when I orginally order all the parts for my amp, the supplier was out of the recommended DSEI12-12A diode, and I opted to go with one with similar specs, although 1000V instead of the recommended 1200V, obvoiusly not knowing about the above referencd problem. So, I just ordered a couple more diodes, this time the ones rated for 1200V and 17A.

In the meantime, anxious to hear my amp make some sound, I decided to switch over to the tube rectifier. So, I desoldered the diodes and jumpered (instead of a switch) the terminals for tube rectification. After rechecking all the connections, I switched it on. I heard a slight hum for a few seconds, then some crackle/pops sounding like they came from some where on the board, followed a blown 3A fuse (my last). Three of the tubes had little glowing orange spots, but one of the EL34 power tubes did not, and if I had to guess, this is where the crackling came from.

So, I'm wondering where I should proceed next for troubleshooting? To start with, it seemed to me that the vacuum tubes went into their respective sockets very easily (too easily), so I'm thinking that I'll use a small pick to tighten up the socket connectors, for fear that they might be loose.

I'll hit up the store tomorrow after work and get some more fuses...

Any and all (no matter how simple) suggestions are appreciated!!!

Thanks,
Eddie
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Old 27th May 2008, 08:31 PM   #2
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Photos?

Double and triple check your wiring. Sounds almost like a short. If you don't find anything odd there then check your soldering. I've done this by using a DMM and the "beep" function to determine continuity.

I don't see why a 1000V diode wouldn't work. I fried my FREDs and plan to replace them with a UF4007 rated for 1000V (mouser 625-UF4007-E3). Perhaps not as high performance, but it should do. I've just not had time to get it on the bench, though.
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Old 28th May 2008, 04:22 AM   #3
w5jag is offline w5jag  United States
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Default Re: Tubelab Simple SE Rectifier Problem?

Quote:
Originally posted by eddiemeddiem

So, I desoldered the diodes and jumpered (instead of a switch) the terminals for tube rectification. After rechecking all the connections, I switched it on. I heard a slight hum for a few seconds, then some crackle/pops sounding like they came from some where on the board, followed a blown 3A fuse (my last).
Check the polarity of your electrolytic caps following the rectifier. You may have one or both installed backwards.

Win W5JAG
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Old 28th May 2008, 01:13 PM   #4
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Well, after tightening up the tube sockets, it seems like Iíve fixed the problem in the one power tube, however Iíve found another. I power on the amplifier (without any volume), and let it sit for ~30 seconds or so, and then I see a blue arc/flash in the GZ34 rectifier tube, and the fuse blows. I checked the voltage out of the transformer that Iím using for the tube rectifier, and itís reading a hair over 6V, instead of the 5V like the spec said when I ordered it. I checked this voltage with the transformer disconnected from the board at the leads, and then when connected to the board at the tube socket. Should the rectifier tube be able to handle the 6V instead of 5V?

While I was at it, I checked the high voltage taps out of the primary transformer, and itís reading about 860V, instead of the 800V like itís specíed out as. FYI, the line voltage at my house is 123V. I know my line voltage is high, I would think that the components/design should be able to handle this?

Anyways, Iím not convinced that these higher voltages are necessarily my problem. Hopefully tonight Iíll have some more time to check continuity and do some more trouble shooting.

I tried to attach a couple of pictures, but I'm having trouble with the file size. I'll find somewhere else to host them tonight.

Thanks!
Eddie
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Old 28th May 2008, 04:01 PM   #5
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The voltages from the transformer should be a bit high when unloaded. A load should cause the voltage to sag down to something more appropriate for the job.

Did you remove your dead diodes? I had to remove mine after they shorted to get the ball rolling.
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Old 28th May 2008, 05:33 PM   #6
Merlinb is offline Merlinb  United Kingdom
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Quote:
Originally posted by eddiemeddiem
I see a blue arc/flash in the GZ34 rectifier tube, and the fuse blows. I checked the voltage out of the transformer that Iím using for the tube rectifier, and itís reading a hair over 6V,
Unfortunately, most of the TubeLab power supplies are poorly designed, so I am not particularly surprised you're getting a problem.
Firstly, what value capacitor are you using for the reservoir? (C1 in the schematic). It should be no more than 60uF.
Second, are you saying that you're using a separate transformer to power the GZ34 heater? If it's an ordinary little 5V transformer then its insulation may be suffering by having the DC imposed on (which could lead to the arcing you see).
There is, of course, a small chance that the rectifier itself is bad.
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Old 29th May 2008, 02:26 AM   #7
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Quote:
Unfortunately, most of the TubeLab power supplies are poorly designed, so I am not particularly surprised you're getting a problem.
Merlinb

Please explain your comment. The power supply in the Simple SE is textbook stuff except for the solid state rectifier option which most builders don't use. What is poorly designed about a textbook FWCT rectifier (5AR4) followed by a CLC or CRC filter?The recommended value for C1 is 47uF which is acceptable for a 5AR4. The Simple SE power supply has been thoroughly tested and simulated in PSUD and LT spice. If it is properly built, it WILL work.

The entire Simple SE design is mostly (old) textbook stuff except for the CCS. There have been dozens of them built with very few problems (3). Except for a few zapped diodes which were caused by the standby switch in the transformer CT, there have been ZERO power supply issues. The standby switch is no longer recommended. There has been only one other instance of a Simple SE that did not work on power up that I am aware of which turned out to be a speaker connector that was shorted to ground.

eddiemeddiem

There should be no jumper in the SW1 connector for tube rectifier operation, although it won't matter if the diodes are removed.

What are you using for a main power transformer? You mention an 800 volt rating which is a bit high. You are measuring 860 volts which is too high. I am guessing that since you asked about a seperate 5 volt rectifier transformer that you are using an Antek 800 volt toroid.

I have connected a Simple SE up to an Antek 800 volt toroid to see what would happen. The B+ voltage was about 525 volts under load with a 120 volt line voltage. You will be getting 530 to 540 volts. This voltage is far too high for 500 volt rated capacitors, and all but the best output tubes. If this is the case be aware that the electrolytic capacitors are capable of violently exploding if operated above their rated voltage. I removed the capacitors from my board and used external motor run capacitors capable of 630 volt operation. Most EL34's can't handle this much voltage, so I used EH KT88's. In the end, I decided that the extra watt per channel wasn't worth the effort, so I put back the 750 VCT transformer and saved the big Antek for a big Push Pull amp.

In your case, one of the capacitors C1 or C2 may be breaking down causing an arc in the rectifier tube and a blown fuse. If the power supply capacitors are not the problem, one or more of the EL34's may be going into a runaway condition at this high of a voltage. Either way the easiest solution is to use a more conservative power transformer. It may be possible to use higher voltage rated electrolytics, but they are hard to find, or off board the capacitors, but then the tube issue will come up. If your EL34's will survive at 500+ volts the cathode bias resistor will need to be increased. Some experimentation will be needed to find the proper value.
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Old 29th May 2008, 03:02 AM   #8
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Probably just hating over yer power supply with the PIC...

Bank switched memory and I/O? One working register?
Poorly filled with an inferior grade of magic blue smoke.

Shoulda gone AVR there.... Dude, I'm tellin ya! Or that
classic Ruskie MCU that executes PDP-11 instructions.
Yeah, that ones the ticket!

I'll only forgive if your next abuses some Nixies.
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Old 29th May 2008, 03:03 AM   #9
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Yes, I removed the dead diodes, then jumpered SW1. I did this assuming that I blew the diodes while it was "open" and running the SS rectifier. I guess I was wrong (not the first time).

The power transformer that I'm using is the big SE Edcors - XPWR110, rated at 400-0-400V and 200 mA. For the 5V heater, I'm running a Hammond 166MS, rated at 5V and 3A.

The C1 that I'm running is a 47uF 500V, while C2 is a 180uF 500V.

I just removed the jumper so that SW1 is "open" and daringly switched it on. The result was the same - it powered on for about 30 seconds, then there was a blue arc/flash in the GZ34, and blew the fuse. It didn't last long enough to try to measure B+. I've got Electro Harmonics EL34's right now, an since I'm still trying to get it to work, I'd rather not risk it... the tubes or my life.

Tubelab - If you're relatively confident that I was aggressive and ordered too big of a power supply transformer, it's not a problem at all. It makes complete sense that that the tubes/capacitors can't handle the voltages. I'll probably go ahead and order a smaller transformer - me trying to learn this hobby isn't worth risking anyone's safety.

Here's two pictures that I promised earlier(I uninsulated the alligator clips for the photo):
http://i223.photobucket.com/albums/d...thouttubes.jpg
http://i223.photobucket.com/albums/d.../Withtubes.jpg


Thanks again,
Eddie

PS - I probably should get my circuts text book out from college and reteach my self how to calculate all the volts/amps at the different points.
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Old 29th May 2008, 04:07 AM   #10
w5jag is offline w5jag  United States
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Quote:
Originally posted by tubelab.com

or off board the capacitors, but then the tube issue will come up. If your EL34's will survive at 500+ volts the cathode bias resistor will need to be increased. Some experimentation will be needed to find the proper value.
To the best of my recollection, when I was diddling with my Simple SE in the mid 500's, I started with 1.3K cathode resistors.

Wired as triodes, GE 6550A, GE 6L6GC, the Chinese coke bottle 6L6GC, and the New Sensor Tung Sol 6L6GC/STR all seemed fine at these voltages.

The cathode voltages went into the mid 50's - a bit past the 50 volt rating of the spec'ed bypass caps, but this never caused any problems.

The B+ would go up close to 700 volts before the tubes drawing power would drag it back down . I series connected capacitors to boost the voltage rating.

An Ei 6CA7 arced so hard at these voltages, that it took out the power xfmr, and ended all the fun , although I have since run them in the low to mid 400's without problems.

Win W5JAG

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