I too found a Beomaster 8000 a few years ago with the right channel dead.

As soon as I found out that a channel was dead, just like you described it, I turned the Beomaster off. So I never noticed any problems with the processor or had relays clicking, but I assume that burned out power transistors can do all kinds of strange things to any circuit and cause voltage fluctuations in other circuits including the processor and then anything can happen.

So with the help of a servicemanual, downloaded from this site, I exchanged the power transistors and a few other transistors on that particular amplifier circuit. Each channel has got its own printed circuit and the layout of the Beomaster is relatively logical, even though patience is needed disassembling and reassembling. When the damaged transistors have been replaced it is very important to trim the amplifier and it is explained in the servicemanual how you do that. The damage to the amplifier could very well have been caused by being "out of trim". Slightly out of trim and the power transistors will get VERY hot, but as soon as the 'No Load Current' and the 'Offset Output Amplifier' has been adjusted properly the heat output should be a lot lesser. The right side of the beomaster is always warmer because this is where the main power circuits are and you will notice that there are also a few power transistors on the display circuit, which also releases some heat. In my case the beomaster was running as it should after these repairs, but you might consider exchanging worn out capacitors and those trimmers that I mentioned before on the power amplifier circuits. Exchanging components on the power amplifier circuits naturally means checking offset currents and voltages again.

My Beomaster 8000 has played happily ever since I repaired it and I very much enjoy it.

Good luck with the repairs

Welcome to Beoworld !

Grab a capacitor kit and replace the lot.
Replace also the trimmers for the DC offset and idle currents and readjust to
factory specs.
Check for cracked solder joints at all connectors on the processor,
display boards and check the general condition of the low voltages
power supply board.
Not the easiest system to work on but definitely one of the nicest to own and use,
not many modern systems can do what this system can.

The same goes for the Beogram 8000 (capacitor kit and solder joints) though
if it works fine there's really no rush.

Martin

Well, I discovered the souce of the bad right channel--the driver board has some cooked parts. The left channel's board looks like it's gotten "warm", as they are wont to do, but not "cooked". The problem with the flaky input switching is not readily apparent, but I'll look for bad solder joints and bad caps. And, there was a loose ground wire, so that may be partly to blame.

Here are some pictures of the guts:

1. Right side output board, behold the charcoal...


2. Left side output board


3. Power supply board


4. Entire insides


5. Toroidal transformer & supply caps


I am so blown away by this receiver--IMHO it belongs in the pantheon of "monster" receivers. The transformer is 6 1/4" in diameter! This is totally different from anything I've ever worked on in the past, but I think it will be totally rewarding as well.

Well, based on the pics... looks like you indeed have found an issue! I would deal with that first.

jhoyt wrote:

The other issue is that after a short time the microprocessor goes on the fritz: the relay clicks open, and I lose all sound. Radio reception goes dead. And after a couple more minutes, the display starts changing inputs and radio presets on its own, then eventually freezes up.

Regarding this... I had similar wonky issues and this thread fixed mine!

Yes, that one will need all components from the drivers (BF857) and outwards replaced as a minimum.
It can be very tricky to get it all right if you are not very experienced and the power supply
won't hold back if something gets in the way electronically so look out for flying parts of
transistor housings etc.
If you are not very experienced with repairs of this type, I would suggest you look for a
complete and working amplifier section. It may be the easiest and cheapest
solution in the long run.

Martin

I have the predrivers on my list to order. Would the power transistors need to be replaced as well? I have not physically seen them, so I don't know what they look like. But there were no signs of overheating on the heatsink.

Before I go to Digikey and place my order, does anyone have a Module 5 they want to sell? 😐

The power transistors are sitting on the heatsinks. They are darlington transistors, so they are listed as ICs.

You cannot tell if a transistor is OK by just looking at it.
I would replace the whole lot.
Even if they still measure fine, there's a good chance that one or more will suffer
from internal scars that will show up as a drastic failure sooner or later.
Watch out for counterfeit transistors. (No joke!).

Martin