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Hi
I bought a white BM1200 which is so good looking.
I bought it as "functioning" but i had 13V dc on the output. I never attached speakers.
I changed the 3000 uf output caps - , that didnt to it - now the dc is 18V meassured between pos. and ground on the speaker terminal.....
The dc powersupply is adjusted to 33V.
I didn't adjust the bias yet, it is about 6.6 mV.
Do I miss something - or is something wrong…?
Br Torben
Burned output stage is the most likely.
Check the output stage transistors and the emitter resistors.
Martin
Hi
Martin, I followed your advice of checking the output transistor, they were all good - nice rca's.
I changed all capacitors in the power supply and oytput stage, also emitter resistors....all adjustment on the 33V voltage and 7,5 mV on emitters are good.
I still have 0 v ac, but 18,4 v dc on both outputs.....hmmmm. The same dc amount on both sides of the output caps.
The schematic is so that there is a 3000 uF at the end of each output stage - just before headphones/speakerterminals...…..
When I meassure with my multimeter for dc on the outputs with no speakers/headphones connected, isnt it so that I will meassure dc voltage "hold" by these output capacitors?
And if speakers where connected, the dc "hold" would dissapear.due to 4-8 ohm circuit? Perhaps with a little Beomaster thumb at power on?
Shouldnt I be good and done repairing - ready for speakers? Im still a beginner in this…..
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