B & O Beocenter 4600 Turntable problems!

[Old Sparky]

Basically, there are two faults with the t/t , one is that it runs at 45rpm regardless of which speed is selected, although the set down position is correct at 12" when 33.333RPM is selected, and 7" when 45 is chosen. This may only be something as simple as a switch fault, but I'm not familiar with this machine. The other fault is that, at the end of a record, the arm doesn't lift clear, so scratches the disc as it returns to it's rest. Does anyone know where and what the adjustment is to correct this, please? I have ordered a service manual from an on-line supplier, but may find that mechanical adjustmen procedures aren't included. This often seems to be the case with many makes!

[Old Sparky]

I've now received the service manual, which does give instructions on how to adjust the record deck. The pickup height is adjusted via a screw in the top of the Arm, in front of the counterweight so that the sylus tip is 3mm above the record surface at the lead-in groove of a 12" LP, whilst the tracking weight is set, after balancing the arm, to 1.4g. In practice I've had to set the height at ca 4mm otherwise the stylus tip scrapes across the disc as noted above. There is still the speed issue of the motor running at 45rpm when 33 is selected. A 3v DC Motor, servo controlled, is used, with the usual switched pre-set pots, one for each speed, sofinding the cause of the fault shouldn't be too difficult (famous last words!!)
Incidentally, when the stylus wears out, the complete cartridge/stylus assembly has to be replaced. On Musonic's website they are asking a whopping £375.00 for a new one, and it would appear to be impossible to fit anything else. Fortunately the stylus on the 4600 I'm repairing is in good condition!

[AlanBeckett]

Incidentally, when the stylus wears out, the complete cartridge/stylus assembly has to be replaced. On Musonic's website they are asking a whopping £375.00 for a new one, and it would appear to be impossible to fit anything else.

I think I'd be prepared to work very hard for that much, or else the Tip

Alan

[Old Sparky]

As a follow-up to my earlier post, I still have the speed change fault. If I play an LP the speed is correct at 33.333RPM. Switcing to 45RPM, a 7" disc is then played at the correct speed, but if I then switch back to 33.333RPM, the 12" LP then plays at 45! Switching the unit off, either at the wall or via it's on/off button, theen back on again after maybe a minute, the LP then plays at the correct speed. Though I haven't confirmed this yet, I suspect that the cause may be in the 33/45 selector panel, since the c/o switch operated by the cam gear is working OK. A further problem with the PU arm not lifting clear of the record at switch off was due to the pin of the lifter sticking in it's bearing, cured by the application of a small amount of sewing machine oil to the brass pin/bearing assembly, with the record deck inverted so that the oil ran down into the bearing. I did it this way to avoid removing the PU arm. The cartridge, incidentally is wired to a mute switch under the deck with some very fine wires, which are not colour coded, and can break off the switch tags if strained!!

Edit; One disadvantage of these decks is that there is no manual play setting, and, AFAIK, the auto mechanism & circuitry treats every 12" record as a 33.333RPM LP, and every 7" disc as a 45rpm. There is no way to set the speed independantly of the diameter, other than under the fault conditon above!, and no way to play 10" discs of either speed. Why this is the case on a machine which cost, I believe, about £400 in the late 1970s I don't know, but then B&O were always different!