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
Despite having worked as a service engineer for over 40 years I haven't been able to find out why the spindle motor doesn't work. When a disc is inserted (playing side uppermost) the loading motor operates, draws in the disc, which is clamped in the play positon for a short time, but the spindle motor doesn't rotate, and the disc is lowered again. I have checked for obvious things such as dry solder joints & cracked PCB tracks, but have found none. What i have found is that 91TR333 & 91TR339 are faulty. Both read completely O/C when tested with a DMM, and the phototransistor doesn't react to changes in the light level to which it is exposed. These items are presumably no longer obtainable, and, if this is the case, with what should they be replaced? The parts list only shows B&O part numbers for these devices, not actual type numbers. Replacing these items with a phototransistor and diode originally used in Blaupunkt Car Cassette players as tape motion sensors, often referred to as 'opti-pulse switches' hasn't cured the fault. Would I be right in suspecting that the HD8805V-A control IC is faulty? I haven't yet checked whether the 4.00MHz Crystal, X302, is oscillating.
Have you cleaned and relubricated motor?
blah-blah and photographs as needed
A correctly assembled Beogram CD50 will only lift up the disc clamp (and disc), if a disc has been sensed.With no disc loaded (sensed), the tray will just drive in and not lift.
Martin
The problem with the CD50 I'm attempting to repair is that, with a disc inserted (playing side upwards) the CD is loaded, clamps in postion, then after a few seconds, maybe more, it drops back down again, because the spindle motor doesn't operate. All power supplies are present and correct, but, as I stated in an earlier thread, the LED & Phototransistor sensors appear to be faulty. The spindle motor spins freely when rotated by hand, so maybe a fault in the servo circuit, or within the motor itself.. Although I have worked for over 40 years in the repair trade, this is the first CD50 I've encountered, so am not familiar with this particular player, so any help with solving the problem will be welcome.
Here is the start up sequence,ie what should happen!
The disc loads and clamps,then the sledge motor drives the sledge/laser assembly inwards until stopped by the inward travel switch.This signals the upc to switch on the laser and search for focus.If this is achieved,the disc motor starts,and if the TOC is read ok,the sledge motor will drive the sledge across the disc,and the track order display will illuminate.You should also of course by this stage be hearing some music.
It's very common for the mode sensor switches on the loading mech to become oxidised,so confusing the upc.I've never had any trouble with the optical disc sensor,but you can check it's working,by monitoring pin 17 of the upc (ic310)which is high with disc,low for no disc.
The laser's are long lived(made by Sony?)and you can check if your's is working by measuring across R101 on the servo board.
I'm assuming that you have the service manual of course?
The disc motor can can sieze,but although it's quite a complex hall effect device ,is electrically robust.
The sledge motor can also sieze,and there were a number and variety of mod's for this.
Overall,a great machine.Basically an Aiwa chassis,extensively reworked and tweeked by B&O to compliment the ground breaking Beosystem 5000 in the mid eighties.
I'v got four of these(mad I know!)and I prefer them to the later Beogram Cd5500.
Good luck with it,it's well worth saving.
Regards,
Nick
Thanks for the reply. Obviously, in principle, the CD50 mechanism operates in a similar way to all other CD players, so I'll recheck the microswitches, etc., to see if I can locate the fault. The sled and spindle motors are OK, and, AFAIK, so is the Laser PU.