Abbey Harmonic II

[jimmy74]

I don’t think the problem is V4, otherwise I wouldn’t get any sound through the return at all right? I know that pin 2 is far too loud to get any measurements, I can hear it humming just by getting close to the pin without even touching it. I’ll try pin 7 again this morning

[jeremyb]

Input jack wired in reverse?

[jimmy74]

Tested pin 7 again... now loud hum just a little bump as soon the tester lead touched it... still getting 38v

[jimmy74]

The input jack was working before... and hasn’t been touched

[jimmy74]

Tried replacing all the preamp tubes and still the same result... very low volume on all channels

[RectifiedAmps]

Work backwards from V4, focusing on which grid pins (2 and 7) make noise when you probe them. Test both halves of V3- if they buzz/hum, go to V2 then V1.

[RectifiedAmps]

The cathode of V3b- pin 8 looks suspect too based on your voltages.

[jimmy74]

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[jimmy74]

Am getting hum on pin 2 of V3...and v1 and v2 are as silent as they come

[RectifiedAmps]

Am getting hum on pin 2 of V3...and v1 and v2 are as silent as they come

What about pin 7 of V3? That grid voltage is strange. Check the resistance to ground on pins 7 & 8 too. It might be a DC-coupled cathode follower as well- pin 1 might run straight to pin 7?

[jimmy74]

Yes pin 7 branches off to pin 1

[jimmy74]

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[jimmy74]

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[jimmy74]

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[jimmy74]

Pin 7 to ground = 20Mohms
Pin 8 to ground = 100k