Right channel noisy. Help troubleshooting

[denti alligator]

A1.  56.8
A2. 366
A3. [no reading]
A4. 57

B1. 51.4
B2. [no reading]
B3. 51.6
B4. 51.6

Clearly there’s a problem.

I was over hasty and added those new caps after the resistance checked out. So that’s most likely where the problem is. I can put the Daytons back if you think that will help.

The one terminal with an off reading is 14, which has 301

[Paul Birkeland]

The 4 pin socket readings you have at B would have me wondering if that tube is properly installed, but at the same time seeing 366 and A2 tells me that you haven't done this on the B socket, but rather you likely need to remeasure. 

The [no reading] should be around 0V, and 0V is a reading.

[denti alligator]

Yes, sorry. 0 for A2/B2.

That 14 terminal is a problem, though, right? Must be related to the resistor I replaced, no?

[Paul Birkeland]

Pin 2 is the plate and will carry the high voltage.  Pin 3 is the grid and will be approximately at 0V.

[denti alligator]

Sorry, for A3/B3 I am getting about -0.17

[Paul Birkeland]

OK, that is correct. 

I would recheck pin 2.  It is highly improbable that you have ~60V on either of those. 

[denti alligator]

Let me do it again. Sorry, I did mix up the pins.

A1.  53
A2. 366
A3. 0
A4. 53.1

B1. 54.7
B2. 356
B3. 0
B4. 54.8

[Paul Birkeland]

OK, the 2A3s are working properly.  What are the voltages on the metal tabs of the C4S driver boards?

[denti alligator]

OK, the 2A3s are working properly.  What are the voltages on the metal tabs of the C4S driver boards?

Which tabs? All of them?

[Paul Birkeland]

Sure, you can list them as big board and small board.

[denti alligator]

Big board

bA 0
bB 0

A +reg 310 and dropping
B + reg 305 steady

A1 384
B1 382

OA 303.8
OB 305

[denti alligator]

Little board

OA 239.5
OB 301.5

1A 304.9
1B. 303.8

[Paul Birkeland]

Ok, that narrows things down a bit.  The regulator seems to be doing its job, but the OB on the small board tells us that the driver half of one 12AT7 isn't drawing any current.  This could be a loose resistor on pin 3 of the 9 pin socket under the small board, a bad solder joint on the small board (it doesn't matter if it has been working for x many months/years, it can still happen), a broken wire, or a loose resistor going to pin 2 on that same socket.

[denti alligator]

OK, I reflowed 2 and 3 on the 9-pin. The LEDs for B on the small board are not lit up. What else can I try?

[denti alligator]

I tried switching the 12AT7 tubes. Now the LEDs all light up. Maybe one of them wasn’t in right?

Voltages for small board are not even:

1A 354
1B 303.7

OA: 285.7
OB: 244.4

I also reflowed all connections on the small board