This is a follow up to my recent post about the redesigned Beogram Commander remote control board, which now works in both (DC-motor) Beogr...
Monday, September 5, 2011
Encouraged by the low currents, I removed the external power supplies, and reconnected the internal transformer (P52), plugged the BM into the mains outlet and measured the voltages at the various connectors. Everything seemed to be as it should!
Encouraged by this test, I connected the microcontroller PCB to the power supply board (P48). and turned the BM on by pressing the "0" bar on the key pad. Life signs! Input selector and volume wheel resulted in the proper display reaction!
This looked pretty good, so I reconnected all plugs to board 6. Then I removed all power connections from the two output amplifiers (boards 5), i.e. I disconnected the red and black single leads (±55V) and the control voltages (P38/39). The purpose here is to prevent damage to the power transistors, which can be fried easily if trimmer R226 is corroded.
I plugged the BM back into mains (I always unplug before changing connectors inside etc...), took a deep breath, and pressed the "0" bar. First light!! It seemed everything was working. Tuner responded, lights came on when filter, mono etc...were pressed on the control board. A healthy double click was audible a few hundred ms after turning the BM on indicating that the two relays in the power supply turned the big transformer on to supply power to the output stages. The picture shows a snapshot of the display. Everything looks good, but the right digit in the frequency display seems to have a dead element (it should read 102.1).
After this life sign, I connected my voltmeter to the output stage supply leads to check the voltages. I measured ±55V as prescribed...a good chance that this BM might be more or less working soon!