So the only issue with the 2400 was that the left channel was a little muffled or thin sounding in comparison to the right. Just not as rich.

So I figured I'd open it up and take a look.

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As I kept digging into the guts of it, I wound up taking off the heat sinks. I thought "how hot can they get if I turn it on for a minute.

Turns out pretty hot. Quick puff of smoke and it shut down on me.

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You might also notice the non-regulation LEDs on the tone control board. Someone before me has been in here and modified those three lights with a mix of LEDs and resistors. Those will get replaced proper.

Now I realize I'm a complete idiot, and I've completely hosed up a nearly perfectly good receiver. The sinking feeling in my stomach is full throttle, and I'm upset the rest of the day. That's the feeling of learning from one's mistakes.

I put the heat sinks back on, while noticing that I never needed to take them off. I flip it up so it rests on the heat sinks, and figure I'll see if this thing will fire back up, or if I've really toasted something.

Well it turns on. So I figure okay, not out of the ballgame yet. What happens if I lean over, and monkey around with the balance slider - ZAP! Shuts down again. Okay great. So I've fried something.

Now I'm researching every single post and forum on no power issues with any 2400 or 1900  I can find. Not fully comprehending any of them.

All signs point to Martin. So I skip the forum questions, and go straight for the messaging.

I realize that long distance troubleshooting isn't exactly effective, but I figure maybe this is a common problem, and there's a typical cause/effect and resolution. What I'm really looking for is "replace this part, should fix your problem".

The questions I ask prompt Martin to gently suggest that perhaps I'm not the right person to attempt this repair.

He's absolutely right. But I'm going to try anyway.

In my head I'm starting to think I've got these cracked resistors next to the heat sinks, I bet that's the problem.

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However, after pulling the cracked emittor resistors, the measurements were the same across all four... must be the large Darlington output transistors. When I pulled those, one of them gave an inconsistent reading across the emittor/collector pathway.

Aha! I've found the answer... or so I thought.

Check the small transistors and diodes in that circuit, change all the Darlingtons

Hey Soren, thank you very much for the input, but this tale has already reached a happy conclusion, it's just taking me a while to get there with my work schedule.

As Soren suggested, I did indeed change all the Darlingtons. And when I tried to start it up, nothing happened. 

So I went back scouring through all the related forum repair threads I could find. Trying to measure different test points, transistor leads, resistors, and whatnot.

Some thread talks about voltages being pulled off TR27. So as I'm trying to get the collector value on TR27...

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My probe slips and connects C and B... and boom, it fires up!

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Now I'm psyched, I just accidentally hotwired it. It's not dead after all... signs of life.

I shut it down to replicate my results, and it starts up again. Sound comes out of the now attached speakers. Making progress, this will be easy!

Back to Martin I went, who again gently suggested that you can't guess your way to fixing an issue like this.

I was pretty bummed out. In my head I'm still wishing there was a simple replace this and you're good, but was slowly realizing that it's not going to happen.

So I took Martin's advice to heart, and kept staring at the schematic. Googling. Symbol definitions. How transistors work. etc, etc.

I ordered replacement transistors for the entire power supply and output stages as best as I could determine.

I was patiently waiting for them to arrive, and as I'm riding the bus to work one day, staring deeply at the sections I highlighted as being the areas to focus on, a lightbulb went on. The schematic no longer looked like gibberish to me.

From day one, the schematic looked like Chinese to me. None of it made any sense. Just a giant bowl of right angled spaghetti. I wanted it to look like the top side of the board, where everything was mapped out as it was attached to the board. Like the backside PCB images in the service manual. that way I thought, I could just match parts up one for one.

In trying to decipher the schematics, I started highlighting the labels that denote the areas they're related to, and circled the PCB numbers to try and orient myself.

So I think I have the output and power supply areas generally figured out so I mark those in pink.

That brings me to the bus where I had my epiphany. I know the majority of you guys will think this is the most basic thing, but for someone who has no idea what they're looking at, this was a monumental insight.

As I'm staring at the schematic from afar, and not at the tiny details, all the blocks took shape. These are drawn almost like city blocks, where each section is in its own little square, more or less. It wasn't until I took a step back that things started to make sense.

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So now rather than replace all the transistors, I figure I'll try to read the schematic a little more closely.

In following one of the troubleshooting threads, I start pulling voltages off the specified connections.

I've got 12V more or less off the mains. Ok.

C92 reads about 22.5V, so I'm still good there.

Test point 16 has nothing, zip, zilch, nada.

Now I zero in on the 15V supply area since that's where everything seems to dead end.

Everything I pull is reading correctly, so it seems all the components outside TR27 are good.

Since TR27 is reading 0V at the collector, that must be it. E and B seem to be reading right, so I'll just pull the transistor, measure against the good one that just came in the mail, swap it out and I'm back in business.

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