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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, September 20, 2014

Beomaster 8000: Intermittent Display Digits - Bad Solder Joints

Oh well...While I was cheerfully listening to an episode of Car Talk on NPR on the Beomaster 8000 that will soon go to Australia, I could not help noticing a couple digits in the freshly restored frequency display fluctuating -on-off-on-off...Back to the bench with this one! It really is a nice workout, carrying the 45 pound behemoth to my electronics lab...;-).

The digits that blinked suggested a problem with the Phase 3 strobe that governs two digits in the frequency display, as well as the balance digit. I quickly found the problem: A broken solder joint at P74 that, among other signals, connects Phase 3 to pin 15 of 9IC3 (the master microprocessor). Here is a picture of the solder joints of the connector:

If you look carefully, you will notice the shadow around the leftmost joint...this indicates a broken out joint.

I re-soldered all jacks and plugs on the two joined PCBs and now all is fine. These two large, but poorly mechanically supported boards are really the most problematic area of the 8000s...whenever there is erratic behavior, it is usually some solder joints or vias on #8 or #9. I will add the re-soldering of the board-to-board connectors to my standard Beomaster 8000 restoration process. Live and learn!

Back to the living room for some more in the field testing before the long journey.

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