Tech 21 - Trademark 60 Problems!! Any Help Here?

[g1]

The problem was not the 'goo', which was supposed to be there.  Rather, the insulator pad must have been cracked or damaged and allowing the transistor case to short to the heatsink.
There are 2 types of transistor insulators.
The mica type are easily cracked and use heatsink grease.  The sil-pad type are flexible like rubber and do not use heatsink grease.
If you had to cut it to size, chances are it is the sil-pad type.
Otherwise, you need the grease like J M Fahey stated above.

[J M Fahey]

Intrigued by this post, searched Heaven and Earth for a Trademark 112 schematic or at least a Power engine 60-112 which seems to be the same cabinet, power amp, power supply, only lacking the multi-emulation multi-effect preamp and sporting only a basic tone control since it's meant to be driven from some multi-effects pedalboard.

Could NOT find anything, these Tech 21 guys are _secretive_ , but one of their designers complained about Yamaha copying their product.

They even use same Celestion 70-80 speaker!

And *that* service manual is available at Elektrotanya. 😉

Different power amp technology (discrete vs chipamp) but the useful point is that power amps have no fancy tricks at all,they are flat and clean (why doesn't that surprise me?), 20X gain (so about 700-1000 mV sensitivity), only slight mod is mixed feedback technology which functionally "changes nothing"

So what's my point?
Now I am *quite* certain your amp literally uses "official datasheet" schematic, so you can use that as a Service Manual.
Not "flying blind" any more. 😊

[Kaz Kylheku]

these Tech 21 guys are _secretive_

When the best name they can come up for a guitar amp is "Trademark", that company is run by IP lawyers. 

A simple-minded rock and roll or metal guy would only think of "Destroyer", "Striker", "Invader", "Ball Wrecker" and such, not "Trademark".

[J M Fahey]

True enough

Under such sheer lack of data, every b it counts.

I suggest OP to post a couple power amp closeups, : PCB showing readable part labels, wiring, power transformer, power supply, etc.

Even if no schematic visible, "counting beans" method may be used: print datasheet schematic and parts list, put good power board pictures by it, go through parts list (as in  R1 ... R2 ... etc), and try to find each part named on PCB, then tick it on both list and picture.

Part numbers will NOT match, but they "must be there" for the amp to work, at least 90% coincidence if not better.

Write on parts list and schematic actual PCB part number.
Say: R1 on schematic is R203 on Trademark amplifier and so on .

Now you have the schematic matching your amp!

You will certainly have a few different/tweaked values but no big deal, you can now repair your amp.