23-03-2017, 09:42 AM
A short while ago I was asked if I could repair one of these Linear Tracking DD Turntables. Having found that a metal pulley had dropped off the worm drive shaft which drives the PU arm, I securd the pulley in place, fitted a replacemen belt to the arm drive mech. and thought 'that's it-problem solved, except that it isn't!! If a record of any size is placed on th turntable and the lid closed, the TT doesn't rotate when the play(Start) button is pressed until the lid is opened, when the TT will then rotate if the lid switch is held or taped down. Could be just a faulty lid switch, a simple momentary push-button type (I haven't checked yet) or , for some reason, closing the lid isn't pushing the switch down enough. However there are other faults - the pichup can be lowered to the play position, but the arm doesn't move across the disc to track it, but remains in the start position. If set to 'auto' the TT will not start, but in the manual 12", 10" & 7" positions it will. This deck makes use of phototransistors & photodiodes for size detection, with holes in the turntable mat set at the 3 standard diameters. All of these items are OK. I've downloaded information from Vinyl Engine, which I'm not sure that I should reproduce here, so have the circuit to hand, but is anyone familiar with these decks, and can they suggest what might be calling these problems, please?
