Punch 45 PC-045C pre mosfet power supply help

[Perry Babin]

The remote voltage comes in and through a 1N4148 diode. Is voltage passing through that diode?

 

[mikep28]

Yes. About .5 volt lower on other side. 14.6 and 14.1

 

[Perry Babin]

Post the DC voltage on all terminals of Q10 and Q11.

 

[mikep28]

I dont have a component desigination map for the amp but the appears in schematic Q10's base is connected to thermal switch so....

Q10: 7.64 13.81 -.216 - when Q5 jumped C reads -1.01
Q11: 7.64 6.94 7.37

 

[Perry Babin]

Disconnect one terminal of the thermal switch and see if it will power up without C5 being jumped. If not, repost the voltages on Q10/11.

 

[Perry Babin]

The early amps uses a thermal switch. Looking at photos, this amp appears to use a thermistor. The thermistor should not read as shorted (the thermal switch should). If is has a thermistor and it reads 0 ohms, it's defective.

 

[mikep28]

it powers up...

 

[Perry Babin]

Did you see post 26?

Does the 3rd op-amp supply switch on?

 

[mikep28]

Did you see post 26?

Does the 3rd op-amp supply switch on?

Yeah the original reads like 2K ohms out of circuit. I thought this amp used a normally closed switch, so the original in fact was not defective..Im assembling the amplifier... But the op amp nearest power supply does switch on....

 

[mikep28]

Amplifier is operational... Bench testing now... So all wrong with this thing was D44VH10 and its driver D0D8. I wasted a lot of time with other stuff when I had it fixed to start with.

Many Thanks again Perry

 

[Perry Babin]

Did you reinstall the D40D8s in place of the A06s?

 

[mikep28]

I left the A06 installed but I put them under the board. Applied some paste on them to the heatsink and put thermal pad on the solder side between the PCB and the transistor. Been on the bench about 3 hours.

 

[Perry Babin]

They should be OK. I've done a lot that way.

I was wondering if the D40D8s were good. It's not important.

 

[mikep28]

Well I know the one that I took out originally was definitely no good. It read as a real pretty resistor. I changed both of them. Still didn't get it to work, then followed your advice. I am pretty confident they are functional parts. I put them back in stock. I would have changed them back out but these boards don't seem to like to be reworked many times. Thanks again Perry I learned something today.