Crown XLS 202 to be repaired

[Roberto]

Hi,

I've receipt a proposal to exchange a working stompbox with a damaged power amp Crown XLS 202.
the schematic is attached and can be found here: https://elektrotanya.com/crown_xls20.../download.html

From what I've been told (I'm waiting the photos), two resistors on the output transistors are burnt, so I guess two shorted MJ15024 or MJ15025.
Are there other common faults together with this damage? Have I (most probably) to expect other issues?
Any suggested replacement for the transistors? MJ21195 and MJ21196 ( https://eu.mouser.com/datasheet/2/30...5-D-107759.pdf ) ?

I'm asking that because I would like to know how much I can expect to pay for the spares, and evaluate if do the exchange or not.
From what I see from the photos and the schematic itself, the 202 could be upgraded to 402 and 602 by adding/changing components and changing the toroidal.
The PCB is the same for all three, just less populated.

Thanks everybody

[Roberto]

I add this link with the description of the circuit and the variation of the different versions:
https://adn.harmanpro.com/site.../XL...t_original.pdf

[The Dude]

It's hard to give a useful answer without knowing how extensive the damage is. I will simply say this. I've worked on several of these and never has it been just a few shorted outputs. Usually damage works it's way well back into driver stages. Expect multiple transistors, burnt resistors, shorted diodes, etc. Also expect to spend quite a bit of time on the thing. If you do repair it, be thorough checking parts the first time so you don't have to start over after the first power up.

[Roberto]

Thank you very much The Dude! This is exactly the information I’d like to receive. The value I’m exchanging is around 50 euros, but I see now the 602 sells used around 150-200 euros, so it could worth just for the curiosity to learn more on solid state power amps.

[J M Fahey]

1) as Dude said, it is NEVER "just replace 2 resistors, 2 transistors and I´m fine".

2) parts cost is NOTHING, problem here is troubleshooting and FINDING what is wrong.
As in: $10 in parts and 20 hours sweating at a bench trying to find WTF is still wrong with the d*mn amp

3)

From what I see from the photos and the schematic itself, the 202 could be upgraded to 402 and 602 by adding/changing components and changing the toroidal.
The PCB is the same for all three, just less populated.

Not in your dreams.
All they share is the *empty* PCB.

All you are getting is an empty rack cabinet, heatsinks and a power toroid ... if you start by dumping the most expensive part of what you got ... then what did you get?

4) compare pears to pears and oranges to oranges.

Compare the value of your working pedal to the value of a working amp and then decide.

A dead anything is worth nothing until repaired.

[Roberto]

Thanks Juan Manuel,

for both three points. I have to say I don't know high power amps so well, nor I have experience in repairing them so much.
Your and Dude's interventions have better clarified the point.

Is there a general troubleshooting procedure for those poweramps that I can study and then decide what to do?

Thanks again!