By popular request (really, I got quite a few emails about this!...;-), I finally completed my Beogram DC motor restoration video! It demon...
Thursday, January 4, 2018
Beogram 4002 (5513): Restoration of PCBs
After rebuilding the arm lowering and tracking systems of a Beogram 4002, my next step is to rebuild the PCBs and replace the reservoir capacitor. This shows the main PCB in its original condition:
This is a detail picture of the RPM control section:
I replaced all electrolytic capacitors with new 105C grade Japanese types, and installed a new relay and 25-turn encapsulated RPM trimmers. This shows the relay and trimmers in old-new comparison:
These components are available to other enthusiasts (like all Beolover parts featured on this blog). Just send a email our use the contact form on the right if you are interested.
This shows the rebuilt board together with the extracted parts:
The trimmers are placed that their adjustment screws protrude through the PCB. This is important since one needs to adjust the RPM while the board is installed and the platter turning.
The next step was to rebuild the output PCB that accommodates the output grounding relay:
I replaced the delay capacitor and the relay, and also installed a switch that allows connecting the system and signal grounds. This is a convenient feature if one operates the deck with a RCA adapter, which often cause some degree of humming. Connecting the grounds often cures the issue.
This shows the rebuilt board:
The final step of the electronics rebuild was to implant a new reservoir capacitor. This Beogram 4002 featured the double capacitance type that is not available anymore.
It has a 4000uF and a 1000uF section. The 1000uF section is only used if a CD-4 board is installed (usually it is not). The 4000uF is essential for the Beogram to run. The black wire in the back is the ground connection for both capacitors. White connects to the 4000uF and orange to the 1000uF ends. I usually replace these caps with a two-capacitor assembly based on a 3D printed adapter that fits into the mounting bracket of the original capacitor:
The 20k resistor across the 1000uF cap serves as a bleed to ensure the capacitor discharges when the deck is unplugged for service or transport. The next step is rebuilding the RPM trimmer panel with LED assemblies to replace its scale illumination light bulbs.