New Crack build, high voltage on T5 and T9

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Checking with tubes out, just to clarify.

 

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Everything checks out.
The wanderers wander into the mega OHMs.
0 OHMs  read 0.
2.9K's read at 2.9.
RCA jack, right = 94 left = 102

 

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Just for fun, i checked temps on the resistors.
The side that is malfunctioning, the resistor is at around 300F.
On the side that seems to be functioning properly, the temp is around 250F.

 

[Paul Birkeland]

You could try a different 6080.  They are relatively inexpensive at Antique Electronic Supply.  What you are experiencing would be an unusual failure mode for a 6080.

 

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I don't know if this is sound reasoning as far as electrical circuitry goes, but I tested resistance (I think) across the 22.1K resistors on 1-2 and 4-5.
The one from T1-T2 measured right at 22K, with no wandering (this is the side where voltage measures in spec). Resistance between T4-T5 wandered all over the place and never settled (this is the side where voltage is way too high).
Is this coincidental to the overall circuit layout, or does it possibly mean something, like the resistor is bad?

 

[Paul Birkeland]

You would I have I think the second bad resistor that I can remember in 25 years.  Are you measuring across the terminals or the actual leads of the resistors?  A bad solder joint could create this issue, or if the resistor was pulled super tight against the terminal strip, it's possible that it was damaged, but physical damage is usually pretty visible.

 

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I'm putting the probes on the leads.

 

[Doc B]

Rub the tips of the probes back and forth on the leads. If there is any contamination from flux or a little oxidation that will cut through it and give a more solid reading.

 

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I put some sand paper to each lead and it still wanders all over the place. (T4-T5)
If I remove the 6080 (and keep in the 12au7), it lands on 22 immediately and stops. Wandering stops with both tubes removed.
Wandering of T4-T5 resumes with 6080 in and 12au7 out.

 

[Paul Birkeland]

Is there corrosion/oxidation on the bottom of the 6080?  If you are running a load of dishes in a dishwasher sometime in the near future, go ahead and throw the 6080 in there and give it a wash cycle.

 

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Got it functioning properly finally (sounds great!).
It is a loose connection in the octal socket. I don't yet know if it is the socket itself, the tube or bad connections/solders on the pins.
It is presently stable, though, which is a relief. Are better octal sockets available which are recommended?
Thanks!

 

[Paul Birkeland]

There are many octal sockets that I don't recommend, like the teflon ones, PC pin ones, etc.  You can get the same socket with solder cups, though I like how easily the fork pins in the ones we use can be tensioned if necessary. 

 

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Ah, good to know! I'll explore tensioning if need be.
Thanks!