Tode debugging

[dave-tx]

Hi - I'm seeing a lot of voltages that are significantly out of spec.  I did have the 10M and the 150 ohm resistors backward at first.  After removing them I ohm'ed them out and they seem to be okay.  So I placed them in the correct locations.  Resistances now check out pretty much spot on.

These are the voltages that differ substantially from those in the manual (spec'ed voltages in parenthesis):
Back T11: 140v (325v)
Front:
T2: 14v (35v)
T5: 15v (37v)
T10: 13.8v (36v)
T11: 137v (325v)
T12: 112v (293v)
T22: 111.7v (295v)

Voltages on the tubes:
A/EL84:
1: 118v
2: 27.6v
3: 14.6v
4: 0
5: 0
6: 0.8v
7: 125v
8: 0.6v
9: 112v

B/EF86:
1: 13.7v
2: 0
3: 0.04v
4: 0
5: 0
6: 27.5v
7: 0
8: 0.04v
9: -0.8v

I may have missed a "-" polarity on some of the smaller readings above.

The EF86 glows, but barely.  I haven't tried plugging in a guitar, some of the readings just seemed way too far off to proceed.  Any thoughts as to what I can look for? 

Thanks,
David

 

[Doc B]

You need to go through the assembly step by step and find your miswire. Either the power supply is miswired or you have a short somewhere.

 

[Paul Birkeland]

You might also want to remove the EF86 and EL84 and do a quick check to see if the voltages around the power transformer pop up to spec (should be above spec without the tubes in place).

 

[dave-tx]

Removing the tubes allowed T11 on the back to increase to 490v.  Does that narrow down the scope of the issue?

I'm going through all of the steps again, as per Doc's suggestion, but am only 1/4 of the way through.  Going to keep going, but if there's a particular area to focus on, I'll do that.

Thanks,
David

 

[Doc B]

Look for a miswire at the tube sockets.

 

[dave-tx]

Well, THIS is embarrassing and I feel silly.  I kept looking and looking for a miswire, but couldn't find one.  Sat down and went over everything everything carefully, then realized that certain LED segments of the most-significant-digit of my meter were burned out.  So a "3" appeared as a "1".  Everything is groovy, and this amp sounds dynamite.  Will have it assembled in the box by tomorrow when my finish dries.

Thanks,
David

 

[Paul Birkeland]

Wow, that's a frustratingly hilarious problem to have, but in the end having gone over your build that carefully will only leave you more confident about the work you've done.

-PB