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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi everyone! I purchased a Beogram 8000 last night via Craiglist (local classifieds), with the knowledge that it had issues. I've been doing board level work for decades (see www.curtpalme.com), but this one I could use some guidance with, as it's my second B&O that I've ever had in.
It came in with intermittent power, which I traced to the power supply solder joints going to the transformer module. While I was in there, I changed a number of electrolytics. I probably should have fired up the Ttable prior to changing caps, but I don't think I caused any problems, and I've triple checked the caps I did change for polarity and value, all checks out. Here's the symptoms:
THe unit powers up fine, and reads 33.33 with the first pair flashing in standby mode. I press play, and I get an audible hum from the motor coils. The platter will spin backwards very slowly, say 3-4 RPM or so. If I leave the player running, the main .3 amp fuse will blow.
I can keep the unit powered up with the motor windings unsoldered. Here's what I've checked so far:
-checked and touched up many solder joints around the main board
-changed the cap next to the CPU chip, checked the ground solder joint (it's solid)
-checked all large transistors, the motor drive transistors, diodes and regulator transistors.
-checked power supply voltages and ripple (both good).
I believe the CPU is fine, as the switch functions work, and before I got into the unit, I did see that the tonearm moved to the play position, but the platter didn't spin even then.
I don't know what waveforms I'm supposed to see on the motor windings, so that's where I'm a bit stuck.
Assistance is appreciated. thanks!
Curt
Hi, Welcome to Beoworld. Check out my thread on a Beogram 8000 restoration and some restorations of the Beogram 8002. Even though they are different turntables, they also share a lot. I didn't run into the problem you are experiencing but it might be worth looking at my threads to see what other restoration steps and adjustments need to be done. To run a quick check without the platter running you can disconnect the P4 connector and put the tonearm through its paces. If the fuse doesn't blow with the platter disconnected that should narrow your search to the problem area. A couple of questions about your turntable...Do you have the service manual and what is the status of the tachodisc on the hub of the platter? A PDF of the service manual can be downloaded from the Beoworld web site with a Silver Membership.
-sonavor
I do have the service manual, and the servo disc is fine.
Thanks!
curtpalme: I do have the service manual, and the servo disc is fine. Thanks! Curt
Good. Now does disconnecting the main board P4 connector allow you to operate the Beogram tonearm functions without any fuses blowing?
Sounds like a constant brake command.When mains is connected to the deck, one of the first commands from the CPU is a brief brake, causing the platter to spina tiny amount backwards (and then stop).If mains is connected without the platter fitted, the subplatter will usually start spinning backwards forever (or until the fuse blows).One guess at a diagnose could be that your deck cannot read the optical pattern on the tachodisc.Either the printed pattern has come off, (in which case a replacement tachodisc is needed - common fault and parts are available), theopto is bad or something in the related circuit has gone wrong.Capacitors, solder joints, tachodisc, CPU socket... all common and all repairable.
Martin
OK thanks for that, it helps to speak to an expert! I mainly do reel to reels at this point. :)
Will report back once i get back into it.
Cheers!