help with troubleshooting the amp on Pioneer Elite TZ-F700 speaker subwoofer

Last night I picked up a set of these from FB marketplace, they were stored for a while so I was not able to test them when at the storage warehouse.

These are pretty interesting speakers and I wanted to give them a try - full review with details: https://www.stereophile.com/floorloudspeakers/148/index.html

Hooked them up and was pleased with the sound, but then I noticed that one of the powered subs was not working properly and was producing very low output with crackling/distorted sound. These have 12" 300W bash powered subs in the base of the speaker - they use speaker cable as input signal. So amp is still not completely dead but has distorted and very low output.

here what the sub/amp in question sounds like


I took out 12" woofer and tested it by connecting it directly to my AVR and the amp in the other working speaker and it sounded fine. then I pulled the amp out and went over every board to see if there are some obvious burned out components. Here is what I was able to find:

1. Missing resistor on input board (indigo PS BASH 630023 Rev 11 amp), someone cut the resistor out?

IMG_7187.jpeg



2. One of the caps on the output board was jumped to one of the resistors?

IMG_7241.jpg



other than that everything else looks fine on the amp boards that I could see.

I was not able to find service manual for the speaker/amp :-(, so any advice how to look for problems would be helpful.

What do the wise diy audio gurus suggest how should I go about troubleshooting this?

What are my options if I can't repair this amp
a) oem replacement amp - these are old and small production numbers so will be hard to find
b) comparable aftermarket amp with similar specs?