This isn't the first time with Tecom and faulty diodes. Remember the large quantities of early DX80's with bad zeners on the PS? We finally just repaired them in house. The failures on the 120 are always DZ1-4. I'm assuming poor quality or underspeced zeners too.

I've had many DX120 failures in the exact same spot. It seems only recently they don't want to repair them. I'd buy the surge bit but many fail right out of the clear blue when I know there's been no surge.

In the case of these cabinets there was no charring of the boards themselves, only surface smoke damage.