Here's a Carlsbro schem that uses the 1C03 in TR6 position.
Unless you are getting very strange HFE readings out of circuit, I would be hesitant to replace it just for that.
There is a 1C04 acting as it's complement in TR7 position, does yours have that?  If so, how does the HFE reading on that one compare?

Was the amp working, or did it have a fault you are trying to fix?

Nice work Phil.
Sorry to hear about your wife.  Hope you can have some peace for Christmas.

Do you have the proper footswitch?  Without it, these amps don't really work right, you get a mix of clean and dirty channels.
TR2 determines what the eq is doing, depending on which channel is selected by the footswitch.  It may be fine, you can look at the pinout for BC184 and see if the correct leads are going to the correct places (emitter to ground, collector to VR6).
Small value caps that are in the signal path are prone to degradation and cheap, so you might just want to replace them.  Or check them with a dedicated cap tester.

You can't just isolate single components in circuits that are otherwise not identical.
The input cap has to do with the other caps and resistors around it, do the other amps have the 100p to ground?
The gain pot bypass cap will affect the frequency response somewhat.
Do the other amps use the TIP100 and 105 output devices?  Those caps in the power amp are for stability.
Not sure if changing the IC would have any benefit. 
Sometimes putting modern parts in old circuits makes them worse, as they were designed around limitations of parts.  For example, chips with better bandwidth or faster slew rate can make amps sound more harsh.

Quote from: Tassieviking on December 03, 2023, 10:17:37 PMhttps://carvinaudio.com/pages/guitar-amp-schematics

Excellent.  From the SX package on that page, the SX50 is pg.14 and 15 of the pdf.

Quote from: smsuryan on December 03, 2023, 08:50:50 PMnot sure how to distinguish where the "blues button" is located and omit the clean channel. 

The blues button puts back the 500Hz that is notched out for metal and hard rock tones.  It is only on ch.1.
It is shown as S1A and S1B around IC's A3A and A8A.
Around Vol.3 pot (which should be labelled Vol.2?) you can see the 500HZ notch circuit with no defeat switch.

With unit cold and load connected, I would adjust so you have no more than 5mV DC across each of R222 and R223.  That would equate to approx. 10mA idle current through the output devices, which should be plenty.  Even 3mV should be enough.
Alternatively, if you had a scope, at low level signal output into load,  you would reduce the idle current till you see a crossover notch, then increase it till the notch just disappears.

The only way Q209 heatsink could have been responsible is if only the base and emitter were of Q209 were shorted together.  This would set the bias even hotter than the factory trim pot allows, as the R226 resistor would be shorted out.

I think it's more likely that the shorted cable was responsible, or there was a solder problem that got fixed in your re-soldering process.

Ok, now I can see the pictures in post #14.  The ones in post #4 and #5 just open a blank page for me.

To drop the 58V down to the 12V zener (46V drop), that 1K5 has to run at 1.4W, so the 1W on the schematic is wrong.  My guess is even a 2W there would run pretty hot and maybe cause some browning of the board, so they just went with the 5W.

Quote from: Tassieviking on November 24, 2023, 01:53:47 AMIt is strange that you are worried about that power resistor that is also 1k5 that is dropping all that powder, there are only 2x 1k5 resistors on that schematic that I can see and they should be 1 watt.

I may have missed it, but I don't think he mentioned a value for the cement resistor?
There are several 7 watt resistors in the circuit and I assumed he was speaking of one of those.

No, he is talking about the SS version.
Look how the footswitch jack connects to a point marked 'X'.
That X goes to the relay he mentioned.

Is this the later tube version (TC) or is it solid-state?
I have a feeling you may be here because it is solid-state. 

Attached is the SS version schematic

A zero ohm reading between components would confirm a connection without flipping the board.

Yes, the 74HC132 is backward compatible for 74132 usage.  The DV is just a brand prefix I believe.
The audio transformer might have been used for mic inputs, as 500 Z impedance is probably close enough to the standard 600 ohm.
Here's one in use for matching PC sound card out to PA mixer mic input:
https://sound-au.com/project133.htm

Yes, a short would have probably created some heat somewhere and maybe even fuse blowing.
Glad to hear you got it working.

Is B-C junction of Q9 giving proper reading on diode check?  It seems like Q9 might be open.