OK, then the ripple?  You have a positive and a negative supply in there.  Are both up to about the same voltage and free of ripple?

How did you check the caps?  Just because the value is close doesn't mean it i well connected.  Sounds like DC on the speaker to me.  If so TURN IT OFF or the speaker will be destroyed.

Does the speaker cone move one direction and stay when you power up?  Take the wires off the speaker and measure for DC voltage between them.

Otherwise check the solder on the main filter caps.  Check the main power rails for ripple.

This doesn't sound like a transistor issue.   They don't age like tubes.  My favorite example of transistor life:  NASA's Voyager satellites.  They run on transistors, and have been running now for 40 plus years in the cold of outer space.   They are way past the edges of the solar system, the temperature is a few degrees above absolute zero, and the little thing keeps sending back messages...it is working.

SO when the fuse/breaker blew, you were playing through teh amp?  Did it just stop in an instant?  or was there any sort of momentary lean up to the blow?  Like a moment of distortion or something?

You replaced a 2 amp breaker with a 1 amp fuse?  Well that doesn't tell me much.  Please tell me it was at least not a fast blow 1A.

Actually weak breaker was my first thought too.  You are throwing parts at it based on possible current surges.  But how about if the breaker is weak, then it doesn't care about peaks.

A fuse isn't a bad idea, but at least use a 2A SLOW or even a 2.5A.

My first reaction would always be check the FX loop jacks.  But I don't think you have them, do you?

I love these amps.  The power amp is on the heat sink assembly hanging from the chassis.  A couple large bolts and it unplugs from the interior board by a 6-pin connector.   Just my guts hunch, but pull that assembly off and check the pins on the connector.  Any cracks on the pin solder?  or just simply resolder them anyway.  Likewise, inside, I think it is the power supply board has the mates for the six pins, resolder those.

It could be anything, of course, but caps don't come and go.  You have a symptom that does come and go.  I'd be looking for a failing connection.  A weak solder joint or a jack with poor contacts.

You have two channels, do BOTH channels act the SAME way?

And just a thought, you have hi and low jacks for each channel.  You likely use just the HI.  Plug into the LOW jack on a channel.  Does that sound like the "problem" condition?  If the cutout contacts in the LOW jack are dirty, the amp will stay in the low condition even using the HI jack.

Perhaps if you told us the make and model of what these parts are in, we could look on the schematic?

You have a good board?  Stick your ohm meter probes on the good one and see what it measures.

Resistors don't burn up on their own, something caused the excess current.   Very often a semiconductor.

CAp, hard to say.  Replacement cost well under a dollar.  WHy take chances?

Did I miss something?  The transformer you link is for a tube amp.  It has a 6v winding for heaters, and a high voltage winding for the B+.   Not suited to a solid state amp.

Doesn't matter, we read them all.

I don't have any solid state Wards drawings.

Is there some thing?  No.  One sets out with a gain structure in mind.  One then decides what sort of voice it wants to have.  Consider the tone stack.  I link below to Duncan Amps page.  They have this really cool "tone stack calculator", a bit of free software you can download.  It sets up several common tone circuits, and offers graphic frequency response in real time as you adjust the controls.  If you look further into it you will find you can even change component values.  And that is ONLY the tone circuit.  Amp designers have to balane MANY factors.

https://www.duncanamps.com/tsc/

You are slinging the term solid state around as if it was the determining factor.  Solid state means it isn't based on vacuum tubes, nothing more.   Somehow I am reminded of my friend who has a little Volkswagen car with a diesel motor, yet I have another friend who drives a large dump truck, also with a diesel motor.   How can they be so different, they are both diesels?

SOlid state doesn't specify much.  Circuits in two amps can be VERY different.  Different circuit, different parts, different speakers (very important part of tone), different enclosures.

I can't see it well, but is the date code on that loose cap from 1975?  40 year old caps can surely make an amp sound crappy.  Just one possibility.

I don't offhand know what is happening here, but be aware that the death cap and switch and related stuff ONLY work to suppress hum from that ONE source.  So if there is a list of twenty sources of hum in your amp, that only works on one of them.

If the heat goop holds the diode in place, that is sufficient.

How is the diode mounted now?

SO it goes on a TO220?  We can lie the diode across the face of it.  If the pc board holes are either side we can just cinch it down, apply some heat grease and rock on.  If the diode is wired to elsewhere, a small clamp under the mounting screw will clamp the diode against the transistor body.

I could be wrong, but I often mark boards when I work on them just for reference.  I suspect your X is really a +.  Someone marked the + corner so they wouldn't have to figure it out later.