Bottlehead Kits > Reduction

Problems with voltages SOLVED AND CONFESSION

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Mmaxed:
I have had my Reduction running for a while now.  I noticed that if I lightly touched the left tube I got a loud crack through the speaker.  Figured it was a bad solder joint so took it to the shop.  Everything looked fine, but I went ahead and reflowed some joints.

Decided since it was on the bench to run the voltage tests again.  All had been fine the first time.  This time terminal 27 which should be 0 volts was a odd, moving around 45 v.  And term 31 which should be 70-90v was 154.4.

I pulled the plug at that point.

Where should I look for the problem?

Paul Birkeland:
Terminal 27 is grounded with a resistor that hits pin 9 on the 9 pin socket.  (1 Megaohm)  I would look closely at this resistor and resolder both sides.

The voltage at 27 creeping up will drive the voltage up at 31, so start at 27.

Mmaxed:
Thanks PB.

Checked out the resistor and resoldered.

Did the resistance checks again.  All OK. 

Put the stock tubes back in for the next voltage checks.  All well on 27 & 31.

When I got to the higher voltage terminals they were all low.
Ones that should be 145-155 were 131.
Ones that should be 165v were 144.
Ones that should be 189v were 157.

When I put the Russian tubes marked 6h23a back in the volts on 27 & 31 went back to what I measured yesterday.  Tube swap side to side made no difference.

Did the AC volt checks on the transformer again.  With everything powered up with stock tubes they were 9.12 v on 4 & 5 and 135.6 on6 & 7.  Slightly lower than originally when they were 9.8 and 142.6.

Do I have a problem with the low readings on the higher reading terminals?

Is there a problem with the new tubes?

Both?


 

Paul Birkeland:

--- Quote from: Mmaxed on October 05, 2013, 12:04:28 PM ---Is there a problem with the new tubes?

--- End quote ---

I suspect so.  That problematic voltage should follow the tube, though when you swap the tubes from side to side, the problematic triode will suddenly be flipped around so that the menacing triode will now be driving the output, not the second stage.

What are the non-stock tubes that you got?

Mmaxed:
Cryoed Reflector 6N23P-EV tubes.  They are marked 6H23A-ED Then under that 0185.  he "A" has no cross bar.

Pretty sure when I swapped them side to side yesterday, that the readings were the same on 27 & 31.

Is it save to put them back in and test again?

Are the lower volts I am now getting a problem?

Thanks so much for the help!

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