There is a switch marked "TEST" at the rear, I think it was on the right-hand side. Try flipping that up and down a few times, it might be oxidized and causing a missing channel.

Okay Ill grab a speaker and give it a whirl... one sec!

I gave it some good exercise, no luck. Same low rumble. I turned the unit on in test mode and it was silent.

Next idea?

I'd say, there is a rumble so something is being amplified, the 3000 is still working in a way. I take it you already replaced all electrolytics?

I would take out the multimeter and compare voltages at transistors vs ground between the working and the broken channel, starting at the preamp. Be careful not to short anything!

Good luck!

Good thinking!

The unit has never been opened. Its the same as it was when it left the factory back in 197X. I was so proud of it, unserviced and sounding absolutely superb!

I will try and get inside tomorrow.

What is the best grounding point inside these things?

Evan wrote:

The unit has never been opened. Its the same as it was when it left the factory back in 197X

That is great (beautiful even!), but in that case, I think you should really put in new electrolytics, these can cause the weirdest faults after 40 years of life because they dry out. If it hasn't caused this fault it will probably cause an other fault any time soon.(Cap kit from Dillen?) It will improve/refresh the sound of the amplifier too, especially if you replace the big decoupling caps too!

If that doesn't help, try the measuring. There is probably a black wire in there somewhere that connects the ground of one PCB to another, I like to use those but any ground point will do, find one you can easily and solidly clip your multimeter to. Never been inside of a 3000 so I can't be much help here!

🙂

The BeoMaster 3000 does not have the red capacitors that give problems, they are the same make as the red ones, but they are grey or orange. I have never had one of those fail. 

You could try to make a recording on a cassettedeck from the tuner of the BeoMaster. If the recording turns out all right on both channels, the input of the BeoMaster is OK, and the problem is somewhere between the input selecton and the speaker socket. A simple way of testing the input selection without measuring!

Ok! Welcome back ladies and gentlemen!

I have a 4 day weekend so I thought I would try and get this project going again and hopefully get a little progress made.

I just removed the wood panel and I can confirm that this unit has never been opened ever before. I happened to look back at the inside of the wood panel and found an unopened yellow envelope glued to it! I sat and stared at it for a while hoping it was money or something but what I found was just as good; an unused, unseen and untouched instruction diagram (part no. 3523053) in perfect condition with no loss of color (as if it would fade in the dark) and absolutely stunning. After looking through the on-site service manual I see that this is regular practice but I've never seen this before. The feeling was very similar to finding the original build sheet to my 1971 Chevrolet wedged between the seat cushions! I want to frame this thing.