I bought a broken M87 on reverb and wanted to share my repair experience:
The broken unit was stuck with no sounds and all the gain reduction LEDs on.
I could get it working by shorting two pins on the ratio switch, but it didn't really compress the sound enough.
First, I first replaced the TLC2262 with a new AD822. This did not change the problem.
Then, I replaced the ratio switch with a new one and now it works. I bought it here: https://eu.mouser.com/ProductDetail/Alpha-Taiwan/SR1712F-0204-20F0A-N9-N-027?qs=8%2Br4Hz5Xir8jgfyVwPHVzQ%3D%3D
I had to destroy the old switch to get it out (very hard desoldering job for an amateur like me).
Without this page, I couldn't have repaired it, so thanks a lot.