Stock Crack Loud Buzz/Hum Left Channel

[Troycnc]

Thank you Derek and Paul or the words of encouragement.
I trashed the LED's and should have a new set Wednesday or Thursday. I am taking your advice and will wait on replacement to proceed.
I apologize for getting ahead of myself with repairs, I am real anxious to hear this thing in action.
I will post again once LED's are installed.
I really appreciate you guys help

[Troycnc]

Ok guys had a little vacation and I am back at repairs. I have replaced the LEDs and my resistance checks are as follows

12u to ground is .1

1-1.158m
2-1.113m
3-0
4-1.087m
5-1.085m

6-0
7-2.989k
8-0
9-3.034k
10-0

12-0
13-.905m
14-0

20-0
22-0

B3-2.989k
B6- 3.034k

R-98.5k
L-100.8K
Ground Tab-0

Hope this info helps with whats going on.
Troy

[Paul Birkeland]

Can you do a voltage check?

[Troycnc]

Thanks for the quick reply,
1-77.9
2-172.3
3-0
4-172.6
5-55.23
6-0
7-102.8
8-0
9-112.1
10-0

[Paul Birkeland]

5-55.23

I would bet from your voltages that both socket LEDs light, but this 55V at terminal 5 is concerning.

Can you very, very carefully measure the DC voltage at A2?

[Troycnc]

Thanks Paul for helping me out with this.
A2 measures 0 volts
The LED Attached to A8 Lights Up
The LED Attached to A3 Doesn't Light Up

Troy

[Paul Birkeland]

Carefully measure the voltage at A3.

[Troycnc]

Paul,
The voltage at A3 is 0 volts
Troy

[Paul Birkeland]

Can you post a photo of the top side of the amp that captures the glowing bits of the 12AU7?

[Troycnc]

Let me know if you need any different angles

[Paul Birkeland]

Alright, how about some fresh build photos?

OV at A2 and A3 with 55V at A1 makes me moderately suspicious that pins A3 and A2 are touching each other, which would short them together, then you'd get the 55V on A1 because of this. 

This should be visible from photos, and you could measure DC resistance between ground (terminal 3 or 12) and A2, then ground and A3. 

[Troycnc]

Let me know if you need more angles or anything clearer.

[Troycnc]

Resistance between 3 and
A2- 2 ohms
A3- .6 ohms

[Paul Birkeland]

Resistance between 3 and
A2- 2 ohms
A3- .6 ohms

Yikes, OK, so a few more tests to really narrow things down.

1.  Pull the 12AU7, then recheck these resistance measurements.

2.  Turn up the volume control all the way, then recheck these resistance measurements.

[Troycnc]

Ok so with power off and 12au7 pulled
Resistance between 3 and
A2-101.3k
A3- 0L