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Thanks orange :dog:

Boy do I feel stupid, I was not supposed to have loads connected yet. The amp was able to go up to 110VAC input no problem with no load and 1kHz input. At 20VAC input, I increased input signal until clipping, and everything was symmetrical. Then I attached the loads, no input, dialed it up to...

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I recently did a very successful White Oak upgrade on a nice PL400 Series II, no problems. That is a very awesome amp now. This left me with a good condition PL-36 board. So, I used this board to fix up a different PL400 Series II that was in pretty sorry shape. I replaced all caps on the...

I explained the problem with a video to the seller. I put a 1kHz sine into the amp and dialed up and down the knob on the front of the amp, showing the problem on the display. This helped with the language barrier. The seller offered to send additional chips or send 60% (3/5) refund. :) So...

Thanks, I only really needed 2 chips to get 1 of my completely dead meters working so it actually worked out. The original good UAA170 I removed from my test amp was still good after unsoldering it. I installed a DIP-16 socket and put the original chip into the socket first to make sure...

I ordered 5 pcs UAA170 from this dubious looking listing on Aliexpress: https://www.aliexpress.com/item/-/32805454426.html To my amazement, they arrived today. They were all scratched up and clearly RECOVERED FROM OLD BOARDS via solder pot! So these are the real thing. I put a socket on one...

Okay, thanks guys, I will leave them in there. :grin:

I appreciate the responses here but looking back now, I did not read the responses very carefully. I don't want to mislead anyone else to think that the diodes are necessary or correct on the PL-36 board. From my small amount of testing with the diodes installed, everything did seem fine...

Thanks Gepetto! I will make those changes. 2 of these PL400s are my dad's (his original one and the 2nd one I got for him) and I just talked mom into buying him a white oak kit. :-P Will be assembling the kit carefully, test it in mine, once it works, sneak it into his and do this cap/diode...

Would love to hear your "guess" orange. :thumbup:

I have been reading about the PL400 latch up, and people say that putting back-to-back diodes across C6 can prevent it. And changing C6 to 470uF helps low end response. I have 3 PL400 Series II's with PL-36 kicking around. I am thinking that they all have the same latch up potential. Would...