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I just finished my second TC-15 build. First, I have to thank Stephen for this extremely cool amp. I found a home for my first one, so I just had to build another. Pix below with voltages just above. My two problems: first, I have 335 V at the junction between the 2M2 and 330k resistors (R34 and R33). Second, I have really nasty scratchy noise on the EF86 channel volume pot. I measured about 100v DC at the pot. Also, this one seems to have significantly more gain than the first one. Any ideas on the high voltage and scratchy pot? I guess coupling cap . . .
I know there was another thread just a few months back with basically the same issues, but nobody seemed concerned about the R33/R34, and no scratch . .. I too have a little high household voltage

______1___2___3___4___5___6__7__ 8__ 9
V1- 137 - - 1.38 - - - - 137 - -
V2- 157 - - 1.29 - - - - 268 - - 171
V3- 253 - - 68 - - - - 252 - - 68
V4- - - - -- 7.98 - - - - - - 365 - 229
V5- - - - -- 7.98 - - - - - - 364 - 229
V6 ---------------------- 376 -
V7 62 - 1.6 - - 102 - 1.6 -

TRy to measure at different Contour settings to see if it goes away. It should, any of those caps will block DC from the plate (pin 6). Check the plate vltage too, betting it's close to 100V.
Sounds like a bad cap in that chain.. that will give a scratch pot for sure.

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Stephen
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thanks - I'll give it a try when I get it apart again. Just put it together for the test run. Sweet! Just like the last one. These babies are often my number 1 goto amp. Love em!

I'll report back when I get a chance to open it up

Dont wait too long to address that DC voltage. I really suspect one of those contour caps is leaking.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

yup, I'll open it up - two of the caps are silver mica, possibly them . . .

Got it sorted - simply had the wire attached to the wrong terminal going from the 6 pos switch to the vol pot on the EF86 channel. It is now absolutely working as it should.

Again, thanks Stephen - and if I haven't said it before, thanks to ZP and everybody else on this forum for the wealth of knowledge you share. I've learned a lot, and I really appreciate all of the resources and help. Great folks here!

Barry

You're welcome and that's great to hear.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps