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...
Tuesday, August 26, 2014
Beomaster 8000: Replacement of a Broken Signal Strength Meter
Ok! Beolover is back in town! I found a very welcome package in the container with the held mail that was delivered by the US postal service yesterday upon my return. This package contained a great-condition signal strength meter for the Beomaster 8000 that I am currently restoring. While I was gone Martin ('Dillen' on the vintage forum at Beoworld.org) sent me this part! As usual, when things get tough on The Bench he was able to help! Thank you very much!
So I set out to put the meter in. Before inserting it, I tried to characterize it a bit for future reference. It seems to be a simple 150mV panel voltmeter with a resistance of 750 Ohm. Its dimensions are 45 mm x 48 mm. There are still some Chinese manufacturers that churn out voltmeters with this form factor. I am thinking one might be able to buy a generic mechanism and put the glass cover of the broken B&O meter on it to make it fit into the control panel cover.
If you look at the circuit diagram, the 750 Ohm create a voltage divider with resistor 2R21 (12k), which imparts an approximate division by 16 to the applied voltage from the IF section, i.e. a good station produces about 2V at the voltage divider, which translates into 125 mV at the meter, yielding a reading of about 7-8.
After doing these measurements, I put it in. I made a short Beolover video about this process. Enjoy:
It seems this went well...on to the remaining restoration tasks.