6260 went from bad to worse
Quote:
Originally Posted by
Russellc
Does the bias voltage drift on the 6230 as well? If so. I'd like to know how to measure and adjust it if possible. Thanks in advance,
Russellc
I am working on a defective 6260 (non fan type).
Here is the scoop, I probed around the drivers and outputs to discover CHA was glitching and relay dropping out at random due to DC fluctuation on that channel. Taking my meter probe to various points in the driver stages would cause it to suddenly become stable. So I did reflow solder on all the outputs and driver stages. I noticed someone had taken a sharpie and marked around the relay and one of the transistors. Probably in the past those had been replaced. After the reflow nothing changed. Ok so now it is looking like prior stages were causing DC offsets at random, perhaps a stage breaking into oscillation? Well no, it turns out IC2 is the culprit. Ok so since IC1 and IC2 are identical and socketed, I decided to swap them around. This puts the flaky chip into CHB. This caused CHA to stabilize but now CHB is jumping around. I should have stopped here with the conclusion that the ICs will need to be replaced.
However....
Still probing around to see if it was some other component resistor etc around IC2 or a bad cap maybe? Nothing changing it still randomly jumping DC to 3 volts bios and then sometimes back to the normal bias. After being on a while POP big spark and it now has blown R19
So of course as are with most high power amps I suspect I will need to look at the schematic and replace everything connected to R19, which means the chip which was failing has now failed totally and over voltage CHB. I now also think there may be a weaker link in the chain as well.
Mostly wondering if anyone else has seen this problem, and did changing out the chips solve the problem? Is it worth the effort to repair this amp? Are their other problems being the problem and not IC2
Now of course am facing more problems that will have to be resolved before it lives and breathes right again. It looks I will be replacing that 27 ohm? R19 resistor along with the associated driver transistor to be on the safe side it would seem it popped when the IC2 finally has failed, and caused a huge voltage swing. I will be diode checking that transistor, and also shows a diode that is off the emitter that if bad will get replaced too. I am hoping it did not blow any of the output transistors.
I would love to get ahold of a parts listing to locate proper parts. The manual I found online has very little technical information to help in repair especially to have a parts list to reference.