Well, I did a stupid thing and acquired a very sad and corroded MAC4100. I stripped it to the frame, addressed all the corrosion and have it back together now including a go through of all the boards.
Everything powers up normal but after about 1 minute the right powerguard led lights up red and this is with the pre/main jacks pulled. I have 20 mv of dc at the left outputs and 50 on the right. I tested the output transistors and they look fine. I also did a diode test on the regulator board transistors and they don’t jump out as bad.
I also notice 23 volts on the regulator board where there should be 18 on pin 17 and 50 v where it should be 48. I can adjust pin 17 to go up from 23 volts but no lower.
So here is my thinking, replace (after testing) the adjustment pot on the regulator board assuming it’s just shot. And replace the driver transistors on both the right and left amp boards. I have already contacted McIntosh parts. What else would need attention?
Like I said, I have a soft spot for orphans.
Everything powers up normal but after about 1 minute the right powerguard led lights up red and this is with the pre/main jacks pulled. I have 20 mv of dc at the left outputs and 50 on the right. I tested the output transistors and they look fine. I also did a diode test on the regulator board transistors and they don’t jump out as bad.
I also notice 23 volts on the regulator board where there should be 18 on pin 17 and 50 v where it should be 48. I can adjust pin 17 to go up from 23 volts but no lower.
So here is my thinking, replace (after testing) the adjustment pot on the regulator board assuming it’s just shot. And replace the driver transistors on both the right and left amp boards. I have already contacted McIntosh parts. What else would need attention?
Like I said, I have a soft spot for orphans.