I recently rescued a bunch of vintage B&O hardware from the scrapheap, among it not one, but two Beomaster 8000's that have possibly not been in use for quite a while.

As expected, there are some issues with these receivers I'd like some knowledgeable input on - I am by no means an electronics expert (some messing with LEDs, arduino, basic soldering skills).

The good news: both cleaned up very nicely, have the original remote and they light up.

The bad:

No. 1:

• no sound from either the 4 speaker-outputs or headphones, regardless of the input used
  
• the volume control worked a few times, then stopped responding
• the tuning dial never worked (both tuning and volume still respond to the remote, so it is almost certainly a failure in the wheels or the processing of the signal from them)
• one defective led in the balance display (not a disaster, just mentioning it to be complete)

No. 2: 

• Fully functional for about 10 minutes total, then a triple plopping noise and no more sound, otherwise all buttons and dials still work ok.

Both now have shaking signal needles at a lower signal strength than before no. 2 stopped working (went from 6-7 to wobbling around 4) mpx light flickers constantly and irregularly in tune with the needle and auto tune no longer zones in on channels. Aside from the dials not responding, the issues of both receivers seem very similar. There was no burning smell, smoke or burnt spots inside (the parts I checked, mainly the backend), which I take as a good sign. No.2 had definitely been opened up before at some point, so perhaps it has had at least some servicing done, No. 1 seems completely original to me.

I humbly request your expert input on possible causes and solutions (does this sound like bad caps?). I'd like to get at least one functional again, I was planning to pass one on to a more skilled enthousiast anyway, one of these monsters is quite enough ;)

No. 1: There might be a defective amplifier in this BeoMaster. If this happens the BeoMaster shuts off the powersupply to both amplifiers which results in no sound.

No. 2: is it working again after a while? The problem can be caused by bad potentiometers for the no load current which can cause the amplifier to switch off or even break down. 

The only way to find out what is wrong is to start find out what is wrong and start repairing the BeoMaster one step at the time.

Is there a particular way to test which of the amps is faulty? It is kind of hard to see what's wrong if there's no power going to either.

No. 2 didn't come back to life after a while, the plopping sound was clearly something giving out - it was only playing at half volume and for just a few minutes, if something overheats under those conditions, it'd be time to dive in anyway.

Another peculiarity I did notice is that it now starts up with the volume at 0.0, I think it used to remember the volume setting (although I didn't get to turn it on and off too many times before it stopped working).

If I am to be really honest, if you haven't experienced B&O stuff previously this system might not be your best start! It really is quite a complicated beast!

I know what you mean. I was kind of hoping it was a known issue, since both BM's are acting similar, but I knew it was a long shot.

I do have some experience with B&O stuff, it's the electronics bit where I fall woefully short. I've opened up a Beocenter 9000 & 9500, Beocord 8000, Beomaster 4500 & 1900, Beogram 1800/4500/6002, mainly for kicks and giggles. The only thing I actually managed to fix that needed fixing so far was a Beogram 4500 turntable with misaligned gears (ie. a mechanical problem). The 9000 had a physically broken cd pickup, so I removed it and lined the opened up space with white leather - it is currently an epic clockradio/watchholder.

The main reason I've been collecting B&O equipment is for the design, if they also work, that's just a bonus. The last few months I've just been buying (and occasionally selling), but now I have all the pieces I wanted and had any chance of affording (BS9000, BL Penta3, BM8000, BM1900, BC9000, RL6000, C75), I finally have time to give them all a closer look, so I might just work my way up if the mood strikes me. The 4500 has a bad tuner, the 9500 has recently completely locked up (lights up but refuses to make any sound, radio defaults to 108.1 and even the sliding doors refuse to open - got it as broken/for parts, so no big surprise). The 1900 only has a few bad bulbs - I think I'll start with those ;)