This amp appeared to be OK. It powers up and produces +22.60vdc and -22.63vdc. I input audio and it produces, but there seems to be some static or distortion. I disconnected audio and started checking.
What is an acceptable deviation from the norm on the +/- 15 volt supply?
Q8 is outputting 14.21 and Q9 is outputting -12.99.
Q8 "adj" voltage is 12.96
Q9 "adj" voltage is -11.73
Could this be part of the problem or what else to I need to check?
What is an acceptable deviation from the norm on the +/- 15 volt supply?
Q8 is outputting 14.21 and Q9 is outputting -12.99.
Q8 "adj" voltage is 12.96
Q9 "adj" voltage is -11.73
Could this be part of the problem or what else to I need to check?
Is there a set voltage drop to set them to or do I just back them down and adjust slowly while watching the amp draw?
Hey!! Seems that it is working good. Clear audio except for some static while adjusting bass and treble. I will clean those good. I also have to repair the power terminals, which were probably the main fault.
This is the old Sil-Pad material from this amp. I'm pretty sure that I don't want to reuse it. Some of the outer layer was stuck to the transistors. This heat sink is a cast material. Will ceramic or mica insulators work on this surface or Kapton tape or do I need to order some of this material?
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On this amp, any of the options will work if you use heatsink compound. Remove the old material (that transferred from the original insulators) from the transistors before applying the heatsink compound.
Just now putting this one back in the heat sink. After doing more testing, I found that the problems with the static and uneven heating of the outputs were because of the .1ohm source resistors. They were way out of tolerance. Only 1 out of the 4 were even close. The first ones I ordered turned out to not be the flame-proof type so I had to reorder.
After installing the new resistors, re-adjusting bias and repairing the input terminals, everything is working great. I am going to use new mica insulators when I put it into the heat sink.
Thanks Perry for your help.
After installing the new resistors, re-adjusting bias and repairing the input terminals, everything is working great. I am going to use new mica insulators when I put it into the heat sink.
Thanks Perry for your help.
I don't know if I'm missing something, but I don't see how the biasing transistors (Q110 and Q210) and the thermistor are held to the heat sink. The clamp bar does not touch them.
They will be OK just being between the sink and the clamp.
The thermistors, however, do need to be in good thermal contact with the heatsink. including heatsink compound.
The thermistors, however, do need to be in good thermal contact with the heatsink. including heatsink compound.