Hi! i got a problem with a Crest CA12 amplifier. This is the situation, the clip LED from one channel light on before the other channel (only when i increase the volume), same audio signal, i switch the preamp boards and the problem persist.

 

Does it sound ok? Is it actually clipping or just the LED acting up? How can you tell?

We need more info. You need to do more basic troubleshooting to further isolate the problem.

Is that possible? Do you have any test equipment?

 

Soundw right all the time, but when it reaches the clip (led on clipping) the sound decrease (limited by the circuit according the schmatics). I only have a multimeter in my hand right now, and the schematics.

 

Look for a clipping level adjustment. If it doesn't exist, you're going to have to dig farther into the circuits.

 

I dont think theres a clip level adjustment, i attach the schematics, im not sure about the circuit that turns on the clip detector, i think it could be Q21 and Q22, what do you think?

http://peaveycommercialaudio.com/media/schematics/ca_schematic_set1.pdf

 

What i've found is a shorted diode (D44) but the problem is still there, i notice if i measure dc in the output (no input, pots at the lowest), in the good channel i have 0V and in the problematic channel -2.9mV.

 

i a also facing same fault in CA12 clip light of A channel is blinking on 70% volume on other hand B vhannrl is wotking ok on 100% volume ! Have you found its solution !

 

Yes i've found it. There was a shorted diode d44, but the reason was 3 pnp power transistors shorted between C-E, i found it after a full check (removing one by one). I hope it can help you.

 

Ok, let me check i will inform you after checking ! Thanks for your support ! Do you have its schematic. Will you plz share it !

 

Ok, let me check i will inform you after checking ! Thanks for your support ! Do you have its schematic. Will you plz share it !

here is: http://bee.mif.pg.gda.pl/ciasteczkowypotwor/SM_scena/Crest/ca_schematic_set1.pdf

 

Hello, i got the point. In channel power board has IC LM311 was faulty, i changed it, nowbits ok ! I will upload pic. Thank you for your kind feedback.