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The PL400 you can do a complete WOPL with White Oak Audio products, including watts abundant protection circuit.
Or do a partial restore mod. The original parts are old and won't last much longer.
I'm guessing the 500 is a Dual 500. Replacing the main caps and...
Getting back to the original thread title, looks like the same fin design as the Carver C-500, only the PL400 had 4 outputs in a row and the C-500 had 5 outputs in a row.
Replaced faceplate on the PL700II with White Oak Black. Black guitar knobs off of Amazon.
I like the slightly darker color rack handles from a Carver C-4000 parted out from Ebay.
The meters have been in the face plate for about five years, installed with the amp in its original design.
My cell phone I used for the pics probably intensified the LED's. They are bright though.