Monday, December 12, 2016

Repairing an Ampeg PF-500 part 2


I was able to install the IRS20957 IC and the amplifier did in fact come back to life! Unfortunately, after some length of time playing at high volumes, it cuts out - first intermittently with some static, then with a loud snap. A brief cool-down brings it back again, though. I wonder if it's not some of the other power supply-related components that are failing intermittently. I would need to run it hard for a while, then leave it on after cut out for a bit to see if it cools down and starts working again. If that's the case, my guess would be the power supply's MOSFETs might have suffered over-current, or I guess it could be that I did a bad job joining the 4227s to their heat sink. At this point, I have everything I need (including know-how) to quickly get into the output section and can do the supply section pretty quickly, too, so I'm not exactly lost in the woods.

I still have that replacement main PCB on order, too...

Updates coming as they are available! I'm working on a Champ 5F1 clone in the mean time.

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