[Dan Alexov]

hoping to get some technical advice to fix a beosound 9000. Picked one up locally for cheap, with stand, cause it had no power. PO said he bought it a few weeks prior and it worked until one day it just turned off (no stand-by, no nothing) – he said there was no smoke, noise – just went dead.
I am a hobbyist and B&O collector and like a project, with much help from google, youtube and forums. After some reading, I opened it up and started diagnosis. I found the fuse on pcb5 (mains relay) was blown. Put a new fuse in, and it blew again instantly. Again put another one in, and this time unplugged transformer first from main board and the fuse stayed good and was getting 9-10V out of transformer. So then found the cause of the blowing fuse was pcb35 (motor control board). So removed it and found TR18 and TR21 mosfets were shorted – replaced those and plugged it all in. Good news is pcb5 fuse no longer blows, but bad news is still no stand-by light if pcb35 plugged in (I get the stand-by if pcb35 is unplugged). so issue is still with the motor control board, but I am now lost what or how to diagnosis it further. any advice? thanks

[Dan Alexov]

update – so after taking a closer look at my sauder job, I cleaned up tr21 sauder and retried – it worked – kind of. First, the standby light stayed on, and the slide engaged with the gear/motor (could no longer be slide manually) and if I hit a cd button the led showed me the cd# and the light went on, but the slide was not moving – also the glass motor kept going up and down (glass was still off). After a few minutes it shut down again. TR21 was shorted again??? Any suggestions now, why tr21 keeps blowing?

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