Stetsom

[Hexhclass]

This amp came in with a broken connection on one of the output inductors. I resolder it now the protect LED is giving me the three blinks which indicates low battery.


Any suggestion?

 

[barber02]

Check the components in the circled area. The remote voltage enters that circuit at what looks like D36 on your board.

 

[Hexhclass]

I have 12v coming to that area but it is from B+.


The diodes test ok in circuit.The 5v for the micro is present



I trace the remote going to an other circuit but didn't spot any fault yet.

 

[barber02]

You can defeat that undervolt error by lifting R127 from the board and installing a jumper wire from pin 8 of the PIC16 IC to pin 14. The amp will do one of two things. It will boot up, letting you know there is a problem with the undervolt circuit, or it will give you a different error code that is most likely the issue that is making the amp think it is in an undervolt condition. That’s what happens most of the time when I have to deal with an undervolt error in these amps.

 

[Hexhclass]

With the jumper in place amp powers up.

The under voltage circuit would be in what area?

 

[Hexhclass]

With the jumper in place amp powers up.

The under voltage circuit would be in what area?

 

[barber02]

The area that I circled in post #2.

 

[Hexhclass]

you have the values of the zeners in that area? D33,D36,D37

 

[barber02]

I don’t have my notes in front of me because I’m out of my shop for a few days. They are 7.5v zenners and the small transistor is a general purpose npn BJT transistor (BC817) if memory serves me correctly.

I did post up some good working voltages for that area on this forum. I’ll try to find them and pull them over to this thread.

David

 

[barber02]

This is from some previous work I did on another amp.

I got lucky and got a Stetsom 8k into the shop that I just repaired and it’s working fine. So I took some voltage readings in the undervolt/overvolt circuit.
Feeding the amp 14.5 volts

D36 K 13.5v A 0.65v
D33 K 13.5v A 5.23v
D37 K .065v A .064v
D31 K 14.09v A 9.95v
D29 K 3.87v A .064v
D30 K .064v A .064v

Linear regulator 14.1 volts in and 5.05 volts out

Q27 B .067v E .771v C .064v
The emitter is connected to ground.

Test points next to the linear regulator

VPP .078v
PGD .075v
PGC 4.9v
VDD 5.0v
GND 0.0v

 

[luigidedom]

If you still have this amp with you is it possible to tell me what U4 and U9 are

 

[Hexhclass]

I no longer have this amp but i will get you the info.

 

[Hexhclass]

U4 2903


U9 IR25607S

 

[luigidedom]

Thanks for the info