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Late Beogram 4002 and the 4004 (Types 551x and 552x), which have DC platter motors instead of the earlier synchronous AC motors usually suff...

Saturday, November 19, 2016

Beogram 8002: A First Look and Restoration of the PCB

Another Beogram 8002 arrived on my bench for some TLC. This one came in a disassembled state:

The hood was removed and of course the aluminum panels are detached (as usual). Under the hood, it was original
except that someone had removed the relay/DIN7 output board:
Luckily, a while ago I was able to buy a 8002 for parts, and its output board will go in here.

As usual the first step of any of my Beogram 8002/8000 restorations is to replace the electrolytic capacitors on the PCB with quality Japanese 105C grade units, and to reflow all the solder points of the board headers. Bad solder joints on this board are the main reason for operational headaches of the Beogram 8000/8002 series. Especially the connector for the transformer often has intermittent pins, causing the platter to randomly stop and other issues. I took the board out
and went to work. The most tricky part of this operation is the sole electrolytic capacitor in the 'inner sanctum', the microcontroller EMI can. It is located right next to the processor chip and serves to decouple its power supply from the rest of the Beogram:
It can be a bit tricky to remove without burning the jumper wires to the small add-on board that sits on top of the capacitor. The important thing to realize about this capacitor is that its main solder connection to ground is on the component side of the board, i.e. one has to do a bit of 'microsurgery' to unsolder it. Having three hands would be helpful here...;-). This shows the board after removal of the capacitor. The small solder pad on the left is the ground connection:
And here after installation of the new capacitor:
Once I forgot to solder the ground connection...an interesting experience...;-)

Here is an impression of the rebuilt board:
And a detail shot of the reservoir caps:
After replacing the board and plugging everything back together the Beogram showed first signs of life. Two issues were immediately apparent: It did not recognize that there was no record on the platter, and then there seems to be a missing display segment:
Interesting topics for the next few posts about this Beogram 8002! 

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