Have you measured the supply voltage to the chip?

There are really only 3 things that can cause this issue - it is a VERY simple circuit.

(1) Incorrect (high) supply voltage - wrong mains transformer, this is a well documented issue

(2) Faulty component in the circuit - there are only about 5 parts - replace them all.

(3) Incorrect speaker impedance or wiring - disconnect the speaker wiring and run two wires directly to a known good speaker.

This is a very easy thing to fault find. First job is to stop guessing and stop wasting parts.

MEASURE the supply voltage with a meter and confirm it with the schematic before doing anything else.

Not much need to - the OP has already determined it is the wrong TX in his machine so we now know the supply voltage to the audio amp/s is too high.

How to fix it without replacing the transformer? Now that's a whole new question.....

It would be great if it was that simple.

The audio amp will pull at least one amp, probably more. A simple resistive divider won't work unless you use 20 watt (or larger) resistors and that is asking for trouble.

The OP needs either an electronic answer using a high current voltage regulator solution or a new transformer.

Maybe you are misunderstanding the problem here?

The Op has found that the incorrect mains transformer is fitted to his machine. This transformer supplies too high a voltage to the audio amp section - too high for the chips and they are exploding.

It makes no difference what speakers are attached - that is not the cause of the problem.

As also pointed out by GPE, there is no easy fix for this issue and it is also a well documented problem.

I don't think you are reading the datasheet for this chip correctly.

It states a MAXIMUM supply voltage to the device of +- 22V (as you correctly note).

This DOES NOT mean it can operate on a supply rail of 44V.

The 22V is plus AND 22V minus with reference to the output pin, 4.

This does NOT equate to a supply rail of 44V.

Don't you think that a simple fix for this commonly known issue would have surfaced by now if there was such a thing?

The simplest solution is for the OP to actually get a meter and measure things, voltages, speakers etc rather than haphazardly replacing stuff all over the place.