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Troycnc · 4395

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Offline Troycnc

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Reply #30 on: August 11, 2019, 12:02:34 PM
Volume down
A2-2
A3-OL


Offline Paul Birkeland

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Reply #31 on: August 11, 2019, 12:06:35 PM
Quote from: Troycnc on August 11, 2019, 12:02:34 PM
Volume down
A2-2
A3-OL
Quote from: Troycnc on August 11, 2019, 12:00:43 PM
Ok so with power off and 12au7 pulled
Resistance between 3 and
A2-101.3k
A3- 0L
The prior resistance measurements needed to also be done with the power off.

Is there any difference in the resistance at A3 with the volume control all the way up vs. all the way down?


Paul "PB" Birkeland

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Offline Troycnc

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Reply #32 on: August 11, 2019, 12:13:39 PM
Prior resistance measurements were done with power off also.
There is no difference with volume up or down between 3 and A3


Offline Paul Birkeland

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Reply #33 on: August 11, 2019, 12:24:08 PM
With the 12AU7 pulled out, you can easily measure the DC resistance between pins 2 and 3 on the tube itself.

You either have debris in your tube socket (quite likely), or you have a grid to cathode short on the 12AU7 (much less likely).


Paul "PB" Birkeland

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Offline Troycnc

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Reply #34 on: August 11, 2019, 12:28:40 PM
I have OL from 2 to 3 shook it around no change


Offline Paul Birkeland

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Reply #35 on: August 11, 2019, 12:46:24 PM
I would bet on debris in the tube socket.  I'd plug it back in and fire the amp back up, then recheck your voltages again.

Paul "PB" Birkeland

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Offline Troycnc

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Reply #36 on: August 12, 2019, 09:36:35 AM
Sorry for the delay, I have cleaned the pins and reinstalled tube. LED attached to A3 still does not light.
Voltages from 12U to
1- 77.7
2-172.1
3-0
4-172.7
5-71.3
6-0
7-102
8-0
9-112.4
10-0


Offline Paul Birkeland

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Reply #37 on: August 12, 2019, 10:35:44 AM
Recheck the voltages at A3 and A2.

-PB

Paul "PB" Birkeland

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Offline Troycnc

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Reply #38 on: August 12, 2019, 11:20:32 AM
12u to
A2- negative 1.342?
A3- negative .014?
And I'm sure I have polarity right on test leads


Offline Paul Birkeland

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Reply #39 on: August 12, 2019, 01:53:28 PM
Quote from: Troycnc on August 12, 2019, 11:20:32 AM
12u to
A2- negative 1.342?
A3- negative .014?
And I'm sure I have polarity right on test leads
Those would be accompanied most likely by yet another new voltage on terminal 5.

Paul "PB" Birkeland

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Offline Troycnc

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Reply #40 on: August 30, 2019, 07:42:52 AM
Hey Guys,
Just giving a update with my battle with this amp. I ordered a new 12AU7 tube to rule it out as the problem.
Just installed and it is dead quiet. This amp is awsome!!!
I really appreciate your help Paul with everything. I will post new voltage and resistance measurements this evening to make sure all is well.
Troy


Offline Paul Birkeland

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Reply #41 on: September 01, 2019, 04:31:57 PM
I would hang onto the old tube too.  Sometimes tubes are noisy, and sometimes the act of tube swapping knocks a loose connection back into operation for a while.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

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