After removing the sub-chassis and rebuilding the transport lock bushings in the Beogram 4004 that I am restoring right now, it was time to focus on the circuit boards and replace the electrolytic capacitors and rebuild the platter motor control circuit. Here are a few impressions:
This shows the main PCB in its original condition:
And after replacing the capacitors with modern 105C rated Japanese made electrolytic capacitors and a new RPM relay and new 25 turn RPM trimmers:
This shows the RPM components:
And a detail picture after installation:
The RPM trimmers need to be installed upside-down that their adjustment screws poke through the circuit board so that one can adjust them while the deck is running.
I also replaced the main reservoir capacitor. This shows the original unit:
And the new one with a 3D printed adapter that it fits into the original mounting clamp:
On to the output board, which on a 4004 also contains a circuit to allow remote control via a Beomaster 2400:
I replaced the output relay and the capacitors, and also installed a switch that allows connecting signal and system grounds if there are humming issues (they often occur when using RCA plug adapters without chassis ground breakout):
That's it for the PCBs. On to the RPM trimmer LEDs.
Hi, what was the value of reservoir capacitor that you used? I am having a hard time sourcing a 4000uf/50v capacitor from my normal sources. Any guidance would be much appreciated.
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