You cannot measure voltages without the components installed.
When you powered it up, did you monitor the idle current(s)?

Martin

Yes, I did adjust the idle trimmers when I started out.  And more recently, I replaced them both because they were original.  The fact that the right channel BDV65B just exploded last time I had it all put together has me nervous about trying it again so I'm going slow.  Can a bad transistor result in this kind of excitement or is it more likely a voltage condition going into a formerly good transistor?

These darlington transistors are a bit strange since it looks like they have a resistor path between the base and emitter so I'm not 100% confident have have a set of 4 good ones to put in!  

Don't get me wrong, but repairing amplifiers like this can some times give even trained and skilled tech guys a good run for their money.
It's not a task for a beginner, and from what you tell us, the terms you use and your working methods, I would say you are not the one to do this repair.
And I say that bearing the greatest respect for DIY'ers.

It could be bad darlingtons, it could be wrong idle current setting(s), it could be a heavy DC introduced somewhere in the amplfiier.
You will need some instrumentation - and not least a good amount of experience to do a repair like this.

Martin

Another thing to consider...
The circuit boards on the Beomaster 5000 (type 2323) are rather delicate. Too much heat when de-soldering can easily cause traces to lift and break. You mentioned using spare parts from other Beomaster 5000 units so it sounds like you purchased several used condition units.  You won't know the history of those boards regarding what other people have tried on those boards before you got them. I would go over all of the traces with a magnifier looking for lifted traces, solder bridges and previous repair attempts. 

Keep in mind that when the receiver was new it was perfect from the factory.  Years later it has failed either due to aging parts (components out of tolerance), some catastrophic event or a combination of both.

-sonavor

Appreciate the advice and I appreciate the challenge.  As has been pointed out, the boards are fragile and the traces lift and I had a few places I had to repair to get things to the state they are in.

But now I have two amplifier boards with all visible issues repaired with darlington's removed and 3 out of the 4 channels measuring the same DC voltage everywhere I measure with my scope.  I'm going to make the wild assumption that 3 are all "good" at this point since they all behave the same way with an outstanding issue on the 4th channel.

When a new set of darlington's arrive, i'll take the gamble on one (or both) of the boards.  Fingers crossed, because if this fails I will be packing it in!

Well a few evenings finally paid off and I have a working Beomaster 5000.  There were several problems, many of which I assume are common with these.

I had two places on the board where previous excitement had burned traces.  One was right off one of the rectifiers and the second one was on the trace that works its way up the right side of board 2.

Some of the foils around the BF857 transistors were broken, presumably from the transistors wiggling back and forth.

I took out all 4 BF857s.  One of them had a short it in and I replaced all 4.  Looking at the PC board, several of the foils around these transistors had lifted because I think this part of the board gets warm in normal operation.  More short wire repairs to double-check all 12 connections and continuity testing to make sure they were in the right place.

Now I installed 4 new darlingtons and set the no-load current to 11mV with new trimmers I had installed.  It powered up, and the left channel worked.  Right was dead.  I traced the signal path and found that TR204 was shorted so TR203 wasn't firing the signal.  In addition, TR201 was not passing on proper voltages so I removed it.  It tested as a functional transistor, but the HFE reading was way less than its partner TR202.  So I replaced the pair.  Now I had a signal all the way through and the right channel was fixed. Woo hoo!

I recapped the amplifier board since I now had it working and replaced the relays on the pre-amp board and the amp board.

Sadly, the remote didn't work and I couldn't find 34 volt on the IR board.  This fault was traced back to an open 100 Ohm resistor in the rectifier circuit (R6) on the amp board.  When I replaced this I had the proper voltage and my remote worked as it should with one exception - the mute key doesn't seem to work.

I tried the mute function on the front panel and that doesn't work either.  Pushing the Mute side of the front panel and holding it does shut the receiver off. Plugging in the headphones does trip the mute relay and shuts of the main pair of speakers.

Digging into the mute circuit now to try to figure it out.  Or, I may just put it back together and call it "99.5% good"!

Did you take out and test the muting relay?

-sonavor

Both relays are new replacements I bought from Dillan.  The mute relay does fire when I plug in the headphones.  It is just not responding to the toggle relay command from the front panel or from the MCP.

I'm looking for a testpoint on the pre-amp board where you might see a voltage change when either of these events happen.  The schematic is hard to read in this area.  There are several places that show two voltages for the "muting" logic, but it is not super clear where these are to be measured.