

I would check all the R33 wirewound resistors as the have tendancy to fail
There is a name for that. It's "munching" (edit - Muntzing) or something. Named after a USA electronics company owner that would walk down the production line and randomly cut out components.
If the device still passed the QA, the component was removed from the BOM.
They all still work ok. TUAC were always changing their circuit designs. I've got 5 TD150 amp modules that are all different, ranging from a few resistors to number of transistors
I have a TD300 amp which is just a TD500 with a pair of output transistors omitted
Both should be 6.3a TD
I would check those smoothing caps on the rectifier boards they would have both been the same and TBH they look well old
Yes. Thanks, I will get some new components today but not the 330pf. Must order again. Some components have the wrong value on board. so I will try follow it around and check. Where do you find the R33 wirewound resistors?
Farnell have a good range but if you don't have an account you may prefer Amazon who seem to have lots.
These would do, they have some that would be a better choice but not on Prime.
https://www.amazon.co.uk/YOKIVE-Resistors-Resistor-Tolerance-Electronic/dp/B0BNBF8CY6/ref=sr_1_9
These are 2W and quite small.
If you plan to drive 4R loads for long periods then you could use 4 in place of each original resistor (2 parallel pairs in series).
I didn't like the look of the 3W carbon film ones at Amazon but the 5W "cement" ones would be OK if you don't mind waiting.
MK