First startup ... Pls Help!

[mlineHK]

thanks paul for having patience with me.  here u go and hope we can find out and correct the problems.

 

[Paul Birkeland]

Neither of your high voltage regulators are working appropriately. Are you able to set the bias voltage for each 6C45P as directed in the manual?

 

[mlineHK]

yes i was able to set both the bias to 145v.

 

[Paul Birkeland]

What are OA and OB on the center PC board?

The 1V at Kreg and 300V at Breg means the 12AU7 in the middle is sucking down nearly limitless current.  The simplest way for this to happen would be a wiring error on the high current C4S boards. 

 

[mlineHK]

i am not sure what u mean by the OA ＆ OB on the center pc board.  the OA connection of the center pc board is a white wire connected to C1.  the OB is connected to A6 if thats what u mean .

 

[mlineHK]

OA 1.6V / OB 1.9v on the center pc board.

 

[Paul Birkeland]

Can you unscrew each of the big C4S boards and post a photo of the bottoms of those boards?

 

[mlineHK]

Here.

 

[Paul Birkeland]

I would add some solder and a lot more heat to all the solder joints on those boards except the ones where LEDs connect.

 

[mlineHK]

ok thanks let me try that first and retest the V.

 

[mlineHK]

hi Paul,

these r the results after re-solder every contact on all 3 boards.


IA A and B 274v
6.3 57v
-6.3 52v
275 275v
Biasing 1.45v


Breg A 273v
Breg B 216v
Kreg A 1.18v
Kreg B 10.66v
OA 1.76v
OB 2.02v

 

[Paul Birkeland]

Resoldering your connections brought one side into proper operation.  I would suggest that you also resolder the center PC board and perhaps that will fix the other side.

 

[mlineHK]

That's what I thot and I have done re soldering the middle board as well. I will redo again and see. 

 

[Paul Birkeland]

You could also replace the 431 regulator on the side with the very low Kreg voltage.

 

[mlineHK]

Thank you Paul will try to replace them.

 

[Paul Birkeland]

Thank you Paul will try to replace them.

It, you definitely don't want/need to replace the working one.

 

[mlineHK]

Yes will replace the a side one.

 

[mlineHK]

hi Paul,

after replacing the A side LM431ACZ ,  the results remain unchanged.  what do u suggest I shall do next?

 

[Paul Birkeland]

Have you reflowed all of the solder joints in the amp?

 

[mlineHK]

All joints on 3 boards only.