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.
Hello Nat,
ReplyDeleteThank you very much sharing your experience on this PF500 amplifier. Very interesting. Finally , did you got it working without cuts out ? I have same cuts out issues with fault led randomly, and was thinking to replace IRS20957.... Did you check which differences between rev J an rev D boards ?
Stephane
I wasn't able to get the original board working without cutouts, no. That's unfortunate, but I think it's because I damaged a trace under a supporting diode - not bad enough to break it completely, but bad enough to cause an intermittent fault or overheating/increased resistance issue. It is also possible my soldering skills were trash at the time; I've gotten better in the last two and a half years, but this was a relatively early project for me, and referencing part numbers and understanding how they work together is one thing, the actual practice of putting them on boards is another. Sorry I can't be more helpful than that...
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