Luxman L-100

[Syedwaqar]

Referred board PB 647

AC from mainTransformer of amp is landing on CO1S...CO6D BUT the DC +_ 55 volts are not appearing (output) at CO7S.... C10S. This seems switching is not establishing in PCB PB647. This +_55 volts leading to (PCB) PB649 connector C11M .. C18M. These +_55 volts seems regulated power for driver transistors.


PB647 is routing DC +_ 80 volts to main Power complimentary Transistors (TO-3) for final output.

Please guide me if I remove the the PCB PB647 and connect direct AC volts from transformer at C01S...C06S , will the output will appear or will be there be any power good signal to initiate switching in PB647.

Waiting & Thanks

 

[Markw4]

Okay, this is what you did before:

I manually started the power supply unit through 4.7 k jumper.
I did not turn the VR901 & VR902 because I was very happy and don't want to change voltage. What I understand that I should trim it if possible to bring the voltage levels to + - 58.

Does that trick still work to start the power supply?

 

[Syedwaqar]

Yes, I manually started the power supply unit through 4.7 k jumper.
I did not turn the VR901 & VR902 because I was very happy and don't want to change voltage. What I understand that I should trim it if possible to bring the voltage levels to + - 58.

 

[Syedwaqar]

I am trying to find where to use the trick of 4.8 k resistance. That loop of 4.7 k is with me but touch points, I forget that. I tried to find from forum history but could not. Please refer me again. Thanks.

 

[Syedwaqar]

"probably" is the keyword.
If most amplifiers survive without that complexity then what is the reason for continuing the personal torment to maintain it there?
I personally would not blink an eye to kick it out.

Maybe I will have time to look at the schematic tomorrow. Pretty busy today.

Okay. Do those connectors carry any of the signals shown in the red outlined area below?

View attachment 1313888

If so, which signals are they? If not, which signals on the schematic are you disconnecting?

C09M..C10M ( Pre Out) is not connected on Pre In of PB649 (PCB). As I wanted to secure the pre amplifier. Any small mistake can turn into fatal.

 

[Markw4]

Do you want to troubleshoot the power supply startup first, or do you want to troubleshoot something else first?

If you want to troubleshot the power supply first, then can you start both + and - power supplies using a 4.7k resistor right now today?

 

[Syedwaqar]

I am avoiding any mistake by wrong move. I want to make sure where to use jumper of 4.7 k on the points. Sorry still not find these points.

 

[Markw4]

You found them before. I would suggest to locate them on the schematic (page 17 of pdf service manual). Are all this pins on each of those connector housings the same signal, just parallel connections?