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Beolover SyncDrive: DC Platter Motor Replacement for Beogram 4002 and 4004 (Type 551x and 552x)

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

Wednesday, December 24, 2014

Beomaster 8000: Rebuilding the Power Supply Board (PCB#6) and a Happy Remote Control Receiver

I always recommend to recap the power supply (PCB #6) board whenever I open up a Beomaster 8000. The golden reservoir cans are often prone to fail at this vintage. Another frequent candidate to interrupt the Beomaster bliss is 6C35 that is mounted directly next to 6IC4 at the voltage regulator heat sink, where it gets nicely warm (but not necessarily cosy for electrolytic capacitor standards...;-). The procedure is largely uncomplicated. PCB #6 can be left connected to the heatsink, and simply pulling it up vertically after removing the plugs from the board gives enough access to the capacitor solder points. The golden cans are usually glued to the board with some kind of silicone-type goo. It can be softened up with a rework heat gun (or a blow dryer) until the cans come loose. This shows the board before I started working on it (note the imposting yellow 'Sprague' capacitor in the top left corner of the board...this helped kill the remote received. See at the bottom of my last blog entry for a better picture of the 'modification' of this board - not sure what the nut who worked on this was up to...it all does not make much apparent sense):

 This shows the board after rebuild with quality 105C caps and removing the offending capacitor:

After this I woke the Beomaster 8000 with the Beolab Terminal by pressing '0' and it came on! All the other functions also appear to work remotely. It appears the remote receiver is back in the game! Beobliss!!

Out of interest, I did some measurements at the remote receiver test points TP5 (input of IR remote amplifier TDA 4050), TP7 (output of TDA 4050) and TP8 (cleaned up 5V digital signal) for further reference. I will post the oscilloscope shots in the next blog entry.

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