Low voltage on right channel

[phunk]

Hello,

I'm having a problem with my Reduction damaging tubes that go in the right socket. It works fine for a while, then gradually the right tube seems to go bad. I redid the voltage check today (which checked out after I completed the build), and the right side readings are about 10 volts lower than the left (the tube in the right socket while I tested is starting to exhibit degradation).

On the right, I have 146.4v on 4, but only 68.5v on 7 and 64v on 2 (and this value is fluctuating).

On the left, I have 146.5v on 29, 78.2v on 26 and 72.5v on 31.

Here are the values for 13-20:

13 67.5
14 67.5
15 68
16 0
17 0
18 78.1
19 77.6
20 77.5

Would this indicate an issue with the resistors that run from 4 to 2 and 4 to 7 or is there another problem? I still pretty new to this, so forgive me if I'm making a leap. If have the full resistance and voltage values available if more info is needed.

Thanks in advance to any that can help.

-Per

[Paul Birkeland]

If you swap the tubes, do the voltages stay the same? (a sign of something perhaps) or do they switch sides?

It's very uncommon to have an amplifier that eats tubes, but off hand I would be looking for a poorly soldered connection, or low voltage (or very high) between tube pins 4 and 5 on one side. 

-PB

[phunk]

Thanks for the quick reply Paul! When the tubes are swapped, the voltages switch sides, so I assume this is just an indication of the bad tube. I have 6v on pin 4 of both sockets and right around 0 on pin 5. So if there be a bad solder joint on the right side, could that cause excessive wear on the tube on that side? Or are my tubes just going bad quickly? I've gone through some NOS tubes a lot quicker than I would expect.

Thanks again,
Per

[Paul Birkeland]

Yeah, I would expect a new old stock set of 6922's or 6DJ8's to go for 15,000-50,0000 hours in the Reduction.

Your socket voltages look good, so that's not concerning.

The other thing that can really wipe these out is if there is much more than 0V at tube socket pins 2 and 7. 

The voltages moving with the tube just helps me to know that there isn't some in-circuit influence dragging the voltages down. 

[Doc B.]

Maybe check the heater voltage at each socket too.

[phunk]

Thanks Paul, that makes sense. I'm getting nowhere near that life span, I on my 2nd set of NOS Vokshod Rockets (that tested fine a month ago, the 1st set went bad in a couple months of listening, but I may have swapped them side to side) and the voltages above seem to show the right one is going out. The first tube I lost was a NOS Valvo that was not so cheap (it was on the right side too)

I will check the sockets pins 2 and 7 on each side tonight and report back.

Hi Doc, can you advise where I check the heater voltage on the socket?

Thank you both for the help, I appreciate it!

-Per

[phunk]

So pins 2 and 7 on both sockets read 0-0.0001V so no problem there. I tested the heater voltage by checking between pins 4 and 5, I'm right around 6V on both, which seems to be good from what I found online. Maybe just bad luck with tubes. I'll try some inexpensive tubes for a bit and see if it keeps happening.

Thanks,
Per