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...
Saturday, July 30, 2016
Beomaster 6000 (2253): First Contact and a New Volume Belt
A Beomaster 6000 (2253) arrived on my bench for some TLC. It came with an indication of 'the volume adjustment makes strange noises'. I opened it up and as expected I found a slack volume servo belt that was not able to drive the volume potentiometer all the way anymore due to slipping. This phenomenon was responsible for the noises when the potentiometer got stuck. I replaced the belt with an EPDM O-ring of the correct size and that restored the volume function. Here is an impression of the new belt installed:
While I tested the units other functions I noticed that the heat sink very quickly developed a pretty high temperature in the center area. This indicated that the right channel at least runs at a too high quiescent current. This is a common phenomenon in this generation of Beomasters due to the often corroded quiescent current adjustment trimmers. As they increase their resistance due to the formation of an oxide film the current gets ramped up. In the extreme this results in a burn out of the output transistors of the respective channel. This means this Beomaster should quickly receive modern multi-turn encapsulated trimmers for long-term stability.