CED VideoDisc and Player Discussion

[Rixrex]

I think this may have been addressed previously, but I don't recall the resolution.

I had somebody give me two SJT 090s, and one worked fine, but the other has a turntable issue.

The turntable, once a disc is loaded, will not spin and does the back and forth wobble, as if it is getting a mixed signal from the motor coil (like AC current flip-flop motion). I suspect something to do with the coil circuitry, but also perhaps the magnetic ring under the turntable. When in unloaded status, the turntable pegs against the disc lift arm. When off, it is freewheeling as normal.

Did this issue ever get discussed before?

[Daxi Don]

Yes, I have seen the problem that Rixrex describes and have fixed the problem on several players. The turntable in the J/K player is direct drive. The ring magnet under the turntable is pulsed to rotate by 4 amplifiers that are switched on and off in sequence by the player Mechanical Micro. When one of the ampifiers has an electronic problem it can cause several operational problems including not spinning and flipping back and forth in the load mode.
Do the following. With the player ON and in the load mode, check the voltages on the pins of IC 5902. If they are not as shown in the Service Manual chart replace the IC. If the voltages on IC 5902 are correct then check the motor coil drive transistors. Check these at test points TP7. TP8 TP3 and TP4. Replace the bad part(s).

[Rixrex]

Yep, I thought as much regarding the coils (amplifiers) from prior experience with AC motors, but didn't think about the IC.

I've got the test meter, but no manual. Anyone with a manual that can supply the voltages?

[SelectaVision420]

does this help?



i assume its a 3 prong transistor, base emitter collector?




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(2)Sears 274 & 934(80150,10&11350), sft100, sgt250, sjt 090-400, vp550, VDR3000, VP2000 & 4000
complete '84 Dimensia Owner