Beomaster 8000: Frequency Dial Not Working

Today one of my friends came over with his Beomaster 8000 in his arms...I restored this one a few years ago, so I felt responsible. The nice bottle of Napa cabernet that came with the Beomaster also helped...;-).

So I put it on the bench and opened it up. A quick test whether the infrared LED in the encoder is toast is by shining a flashlight into the encoder to temporarily 'replace' the LED. The IR receivers in the encoders are somewhat sensitive to white light, i.e. they work with a strong LED flashlight. If the encoder works with the flashlight, the LED is toast (see my entry about fixing these LEDs: http://beolover.blogspot.com/2012/07/beomaster-volume-encoder-repair.html)

In this case the flashlight did not do anything....so I checked the encoder outputs on plug P79. There I got the proper 5V square waves, i.e. the encoder was working.

The next step was to measure the signal at the Schmitt trigger (HEF40196B, 9IC7). The signal arrived there...so on to 9IC3, the master microcontroller. And bingo: no signal at pins 13 and 14. This meant that in both A/B signal paths from the encoder the vias died...

It occurred to me that back then when I fixed this Beomaster up, I did not yet routinely rework the vias on the microprocessor board (PCB #9) when restoring the 8000.
So, I re-soldered all the vias on the board (I assumed the others were probably also close to no-contact...), and everything was fine!

Beomaster 8000: Repair of a Broken Phono Jack with a 3D Printed Insert

The input jacks (sockets) of the Beomaster 8000 are weakly designed. They are made from a plastic that gets brittle over the years, and frequently the tabs that fix the jacks in the socket panel break off when a phono or tape plug is inserted. When that happens the jacks fall into the panel.

So far the remedy was to obtain a replacement from a carcass...a saddening thought. Beolover has a no-carcass policy! Parting out one should really be the very last resort!

Luckily, the 1980s designers of the jacks had a few looks too many at the cheap American cars that were made during this period (remember the Dodge Omni??), and that inspired them to also cheap down their design of these plugs.

To save plastic, they introduced recesses below the jack surface, which probably reduced the weight of the jacks by about 20%. It occurred to me that these recesses could be used to anchor a 3D printed insert, which would restore full functionality and get close to the original looks of the jacks. I made a brief video about the repair procedure (some pics are below):

The STL file of the inserts with printing instructions can be found on my website at www.beolover.com. I will also be happy to supply this part on request.

Here is a pic of the broken jack:

And with the 3D printed inserts in the recesses:

And after re-installing the jack together with the inserts:

It looks and feels pretty much like an original jack...there is a slight irregularity across the surface of the tabs due to the 3D printing raster. Oh well...it is never perfect! We can only strive!

Beomaster 8000: Wire Bridges on Microcomputer Board (#9) and Broken Phono Jack

Before I put the Beomaster 8000 back together for a test-drive in the living room together with his play-pals, the Beocord 9000 and the Beogram 8000, I cleaned and de-oxidized all the contacts on the microcomputer board (PCB #9), and had a look at the inner sanctum, the EMI shielded processor cans. Usually one needs to re-solder the few vias that are on this board, since they tend to be poorly soldered...clearly in the 80's the PCB technology was not that advanced, yet. Anyway, what I found in this particular Beomaster was remarkable. Someone already had put in the B&O recommended wire bridges (and then some...), and they were directly soldered to the processor pins. Unbelievable! Here is a pic:

While the soldering appears to have been carried out with some capability, I would never do it this way...the only parts of the Beomaster 8000 that are truly non-replaceable are the microcontrollers that contain proprietary coding, i.e. one would have to extract the code from a working one, if one would want to attempt replacing it with a NOS chip...

Anyway, clearly, this needs to be left as is. I could not risk to expose those rarefied microcontroller pins to another heat-cool cycle. In a way, since the chips survived this assault, this solution is probably the most reliable...several fewer spring based contacts in between the controllers and their slaves...so I decided to just replace the two electrolytic capacitors on this board and move on.

Here is a pic after putting in the caps:

The last thing that needs to get fixed in this Beomaster is a broken phono jack in the 'socket panel' that lost its tabs that prevent it from popping into the panel when trying to plug in the Beogram:

I am working on a creative solution, since not even Dillen of Beoworld.org has this part available.  He said it is rare, since it often breaks...Another day, another 3D print...;-)