finished stereomour II amp

[Paul Birkeland]

Though that is completely wrong, it would not prevent B+ from appearing on either 4 pin socket. 

Can you post the voltages on each 4 pin socket for pins 1-4?

[Smoses01]

A1: .007 dc
A2: 0
A3: -.0.963
A4: .006

D1: 64.84
D2: 386.6
D3: 0.020
D4: 64.88

[Smoses01]

It seems pretty clear that the D socket is getting normal voltages, while the A socket is not. I will recheck all connections that convey power to the A socket. Thanks for your help in diagnosing this problem.

[Paul Birkeland]

I would follow the DC voltage along the 130 ohm resistors as it goes toward the A socket to see where it's dropping out.  Do also be aware that a missing or loose black wire along the same path would create the same problem.

[Smoses01]

A1: .007 dc
A2: 0
A3: -.0.963
A4: .006

D1: 64.84
D2: 386.6
D3: 0.020
D4: 64.88

One other question- I continue with no LEDs lit on the C4s board. So, would that be connected to no B+ voltage on The A channel or is it a separate issue entirely? Since the C4s board processes the sound signal To the small tubes, you can have B+ voltage ok to the 2A3 tubes, (the output tubes), but no sound signal being processed to the first stage tubes.

[Smoses01]

A1: .007 dc
A2: 0
A3: -.0.963
A4: .006

D1: 64.84
D2: 386.6
D3: 0.020
D4: 64.88

One other question- I continue with no LEDs lit on the C4s board. So, would that be connected to no B+ voltage on The A channel or is it a separate issue entirely? Since the C4s board processes the sound signal To the small tubes, you can have B+ voltage ok to the 2A3 tubes, (the output tubes), but no sound signal being processed to the first stage tubes.

[Smoses01]

Would resistance between black and blue wires of 620k ohms for both Channels be reasonable figures? I configured my chokes for 8 ohms.

[Smoses01]

Re-tested impedance on each plate choke and I am getting 6.2 ohms on each side.

[Smoses01]

Correction on rechecking each side reading 6.2 ohms impedance between black and blue wires from plate chokes.

[Paul Birkeland]

I would focus on getting the DC voltages correct on the 4 pin sockets first before worrying about the C4S board.

[Paul Birkeland]

Would resistance between black and blue wires of 620k ohms for both Channels be reasonable figures? I configured my chokes for 8 ohms.

That would be your output transformers, not your chokes.  I would focus on tracing the B+ along the 130 ohm resistors to see where it's dropping out and not be too concerned about the chokes right now.

[Smoses01]

I have checked where voltage drops off: here is an overview of major high voltages I got, as well as areas of concern that are starred: thanks for any assistance that can be given!

Voltage checks:

*1-2: 0 volts dc
14: 170-230
19: 418
20: 418
20: 385
*27: 0 volts
*30: 0 volts
31: 418
34: 418
IB: red wire to printed circuit board: 418v


 

[Paul Birkeland]

44 and 30 aren't connected properly by the 130 ohm resistor, it's missing, or it has burned up (which would be very visible).

A blown plate choke would give you 400V at terminal 27.

[Smoses01]

Big goof! I accidentally shorted my power supply! (Sparks and loud pop). Now I have no B+ power on the side was working correctly. Interestingly, voltage checks to primary and secondary are normal.  Also, I’m still getting high voltage 400 volts at the rectifier right at the connection
To the power supply. Checked the tubes and they appear to be ok. I think that I will need to replace the power transformer and any other parts that you think may have been damaged with the short. What do you think? Thank you!!

[Paul Birkeland]

I think that I will need to replace the power transformer

Why?

If you read back through this support thread, repeatedly you have asked to purchase replacements of the most expensive and most difficult to replace parts in this kit, and there has never been any data presented on your part that would necessitate having these items replaced.  Even in the event that one of these parts needs to be replaced, we have to sort out here why it failed in the first place so we don't sell you an expensive transformer only to have you install it immediately damage it in the same manner that caused the original part to fail. 

Any parts requests like this that get sent in will get reviewed pretty carefully so we don't end up in this situation and also to be sure we aren't replacing components that haven't actually failed.  We also have written into the manual a set of checks to verify proper operation of the power transformer and performing these tests is the first step (but not the only step!) in determining if there's a power transformer problem.