ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
One of my Beolab 5000s has developed a fault. At volume 20, it plays for maybe 10 minutes before shutting down, and the display flashes "ERROR / TURN OFF". That won't go away until I unplug it from mains, and after reconnecting, it again works for a while. When muted or at volume 2 or 4, it seems to stay on indefinitely.
It sounds completely normal and doesn't feel any warmer than the other speaker that works, so I suspect this is a problem with the overload protection circuit tripping needlessly. I haven't taken the speaker off the wall yet - I'm expecting bad solders or cooked caps, but is there any known problem spot I should look at?
--mika
You will find several bad solder joints. Look carefully.
But another problem will be the powersupply caps. They need replacing. Probably one of the 2 inside (3300uF) is less and can cause malfunction, like clipping.
Thanks, Beobuddy; sorry for not acknowlegding your tips earlier, but I didn't have any time to touch the speaker until today. It's connected to my BS6500, so last month I just rigged it up as a passive speaker to wait for better times.
Today I opened the amp and went through all the electrolytics. Surprisingly, they all measured good or excellent (ESR) so I let them be. I resoldered the output module entirely, including the NTC on the cooling fins that was giving funny readings (probably just oxidized solder surface under my probes).
I reconnected it and eventually it still shut down. It's not heat related, as the only things that even warmed up at all were the relays. Measuring around the safety circuitry, I noticed that it was hyper sensitive; my cheaper DMM on 200VDC scale tripped it every time when I tried to measure the voltage on the base of TR403 and touched it with the probe.
The leads of the transistor (BC557B) were too short for the socket in my tester, so I just replaced it. The DMM still trips the safety circuit if I do as above, but the actual fault seems to have gone. The amp has now been playing for an hour at good volume into an S80.2, so I think I'll just reassemble it and be happy If it still acts up in the future, I guess it is time to look at the TR401/402 circuitry, which apparently is supposed to detect overload in the speaker output.
Mechanically, this amp is surprisingly service friendly. I expected much worse.