Beomaster 8000 main relays not turning off

Hi to all,

 

Another BM8000 problem (Maybe it will get more commons now after 40 years)

 

I’m the proud owner of a beautiful Beosystem 8000 that I partially “restored” about five years ago. More precisely, the Beomaster 8000 has served me well, without any issue, until a few months ago.

 

About 8 months ago, the unit started to turn itself off intermittently, on standby, for no reasons. I tried to reflow some of the vias on the microcomputer board and the problem completely disappeared for the last 8 months. Until last evening :

 

Yesterday the display went blank and the input switched to FM (I assumed it was FM since there was static noise) without any response from the keypads. I then unplugged the unit (with that creepy noise of both amplifiers still on.)

 

A few minutes later, I turned it back on and everything was fine. Switching the unit off showed the standby dot and both relays were turning off. I thought : Intermittent problems, maybe those vias again.

 

Today, I decided to open the unit and have another look at those vias, but from the back of PC9. I then realized for the first time that jumpers were already placed to avoid those intermittent problems. So maybe, after all, my first attempt did not solve anything at all and I was just lucky during those last eight months. Since I was there, I reflowed those vias again, from behind.

 

 

After replugging the unit everything went back to normal : all access, all inputs. When standby is pressed, the unit goes to standby BUT I don’t hear the “click-click” sound of the relays that removes the power from both amplifiers : Both amplifiers are still on, even on standby. So when I unplug the unit, I have that crappy noise that does not feel healthy at all!

 

I’m starting to wonder if I still have the patience to overcome this problem with my amateur knowledge. This machine is/was fabulous, but I realize there is nothing more reliable than my faithful Beomaster 2400!

 

Now, before I put the thing in a cardboard box, does anyone has any advice on were to look, so I could dream of solutions, overcome the problem, be proud again, and wait for the next problem to arrive.

 

Thanks to all for your help

 

Guillaume

 

I sent you an email.

John

Thanks John for your input

It seems I just solved my problem... This morning, when I woke up, I tried to launch the test program by pressing "Monitor" and "Standby" at the same time, as described in the service manual. I got TE 12, which points to a defect 9IC4 or a short Ic pin to chassis (pins 14, 15, 16, 17, 18, 19, 20.)

I was suspecting pin 16 since it's related to the activation of the +-55V rails. I thought, maybe that the solder blob created by inserting the jumpers was touching the back of the metallic cover placed above the components, on the back of PC9.

You can see these solder blobs here, circled in orange :

I removed the bottom can and got back every functions! I replaced this can but I've let more room so it's not touching anything inside. It means that with time, the heat and cold probably displaced the cover somewhat, or bent the PC board, leading to this intermittent problem.

It was not that bad after all. I hope i'll be out of problems for a reasonable time now!

Guillaume

 

Good troubleshooting work Guillaume. So many problems have with this Beomaster end up being a connection problem.  Either some unwanted ground somewhere or some signal not making contact. That was a nice deduction and fix.

John

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Thanks,

I'm happy I got it back to work. I spent so much time on the whole set back then, I couldn't stand at the idea of keeping them only as pieces of furniture, nor at the idea of swapping the BM8000 for another receiver.

However, I perceive the 8000 set as one that could give up at any time : It always surprises me how beautiful the package is, but how nightmarish and compact the electronics fits in. I'm super picky when using it, I always switch off the power bar when it's not in use (I use it only during the weekend) I never go above 4.0... It's like as if I'm not confident about it.

My everyday system is composed of Beomaster 2400, Beogram 4002 and Beovox S45-2 : now this one is always on standby mode, ready to do anything : I'm super confident about it.

But getting back to the 8000 system is always a pleasure and it's indeed a fabulous set... only when there's nothing wrong!

Guillaume

 

Guillaume,
Is your Beomaster 8000 microcomputer board rear cover missing the paper insulator?

The rear, metal cover should have an insulator on the inside to prevent anything on the trace side from shorting.

 

Hi John,

No, there wasn't! I was not aware of that. Perhaps it was removed when the jumpers were added in the past. After i've put back the cover yesterday, I had another case of this short so I added a piece of elecric tape, under the cover, right above this location. This original solution, however, seems to be more elegant though!

That is one problem with a lot of used audio gear.  You don't know the history and odds and ends may have been removed and lost.  One common thing on the Beomaster 8000 are the three flat, metal springs under the release rail (the black metal bar you press to open the tone & filter controls).  Almost every Beomaster 8000 I have come across in the last three years was missing at least one of those springs.

John