The trimmer is set at an extreme.
Always center idle current trimmers BEFORE powering up and adjusting.

Maritn

Ok, I'll try that tomorrow and see what happens, thanks.

Ok did that, instant blow again....😮

Something somewhere isn't happy.

edit...

Just did a bit of poking around - I get continuity between C&E pins of TIP141 and TIP146 on the left side, but not the right.  I gather that is bad. 

Possibly not related, but an observation from running the stereo previously, the right side heatsink would get a little warm, and there was no perceptible warmth in the left.

Hard to tell at first like this but the mica behind that TIP141 looks really crooked.

A blowing fuse indicates a short or an overload.  Check if you bridged traces accidentally when soldering.

Time to check those output transistors... 

Beo_Jean wrote:

the mica behind that TIP141

Is that the white stuff?  I'm guessing that is a type of thermal paste?  It's pretty dry and flaky on all of them.  I do have some modern paste here I was intending to use when finished.

Ok, so I removed TIP141 and it's toast.  And I am pretty sure TIP146 suffered the same fate.  I removed the trimpot and inspected, but all was good.  Installed a new one anyway.

So, next couple of questions are - what is the modern equivalent to the TIP141/6. I can get TIP141s easily enough (most sites list 141G).  TIP147 is available and seems like it might work.  https://au.mouser.com/datasheet/2/308/tip140-d-1196132.pdf

Last question, should I replace the 2 blown or all 4?

TIP 142/147 are fine.

I would replace all four

Beo_Jean wrote:

TIP 142/147 are fine.

I would replace all four

Cool, thanks.  I did find some 141/6s on ebay from HK, about $30 for 10 pairs, ST and ON mix.  Or I can buy 2 sets (4+4) of 142/7s for $20 from local supplier, again ST and ON.  I like the idea of having some spares in case...

Other than that, I couldn't find anything obviously wrong.

I would advice against buying from Asia. The risk of getting counterfeit parts is huge.
Indeed the price you have been quoted is more than suspicious.
Buy from a trusted supplier and expect to pay around 4-5 euros a piece for the real thing.
Personally I would dig through the dungeons for a good used original pair and if that fails I would probably order from Little Diode, from where I have ordered countless times and never received any counterfeit parts.

And why would you replace the two in the unaffected channel?

The trimmer is most likely still fine. But its initial setting was at max idle current, which could easily be the reason for the burned output stage.
Didn't you monitor the idle current at power up? (And replace the trimmer in one channel at a time).

Martin