CED VideoDisc and Player Discussion

[losunge]

Every four or five seconds the color messes up. It alternately flashes no color then the spectrum across the screen for a second, then goes back to normal for another four or five seconds and repeats.

I've taken it apart and played a bit with the belt and put it back on. It seemed fine. And when I played a disc immediately afterwards, it worked fine. Now its having trouble again.

Can anyone offer a more permanent solution?

Thanks,
Zach

[RT9342]

I couldn't tell you the exact problem, but having a Zenith myself, as well as having rebuilt two RCA SFT-100s (which are the EXACT same machine only with a different shell over the guts), I may be able to give you some ideas. I do know that if the picture constantly looks like a spectrum or is black and white then the motor is most likely out of alignment (unless the belt is bad, of course). You can raise or lower the motor by adjusting the mounting screws, which will fine-tune the turntable speed due to the contour of the motor shaft. But if it's intermittent, I'd say it's one of three things:
1) the speed is just a little bit off,
2) the motor is going bad (this happened in one of my SFT-100s), or
3) there is a problem with one of the motor's microswitches - I think off the top of my head which microswitches are for the motor, but you can trace one of the motor's wires to the right switches. One switch kills power to the motor when the load lever is not in play position, and the other kills the power when there's no spine in the player. If these switches were to get dusty, worn, or out of alignment, they could cause the power to the motor to cut in and out. I've never had this problem with the motor switches, but I've had this problem with the SIDE 1/SIDE 2 indicator switches, as well as the RF modulator switch.
Please let me know if any of this helps get your player fixed.

[RT9342]

Just to update my last post: I looked inside my Zenith last night - first of all, I'd make sure that the belt is not stretched and that the turntable has no worn spots. But if you end up suspecting the switches, here's where to look for them: if you set the player to LOAD and pull the tonearm forward, you'll see 2 switches with zig-zag metal tabs sticking up from them (they're to the right of the stylus brush). When you switch the player to PLAY, the left switch, if pressed will signal the computer to start, while the right switch turns on the motor. Also, under the turntable, on the right side, are 2 switches (behind a cam that moves with the OFF/PLAY/LOAD lever). One is the power switch, I believe, and the other is the motor switch. I didn't check to see which one is which, being that it requires removing the turntable - hopefully that's not the problem. But before working on the switches or the motor, please UNPLUG THE PLAYER, as these wires carry line current.

[mario]

On the SFT/SGT models, (including zeniths) in regard to the picture going to black and white or fuzzy it may be the speed of the turntable. These units have a magnetic strip on the inside diameter of where the belt drives the turntable. This strip helps to synchronizes the 60 Hz motor at the proper speed. If the strip is missing or the magnet is weak, (should hold a
paper clip) it could cause the motor not to sync.
Also, there are two metal tabs attached to the motor that protrude up into
the TT ID and should be within 1/8 of an inch to the Mag strip. If this
is out of adjustment it could also cause the motor speed to vary. If the
magnet is weak or the tabs are too far away they can be adjusted by
loosening the screws retaining the tabs to the motor and relocating them
closer to the mag strip.

I worked at the RCA plant and was the Manufacturing Engineer responsible
for the magnetizer and most of the subassemblies. Locating the two tabs as close to the strip was not easy since the motor laminations were not
always flat and the tabs were not always bent to spec. Without fixturing,
this is not an easy adjustment since the turntable must be removed and it
is typically trial and error to get the tabs as close as possible to the
strip.
mario

[RT9342]

Interesting...I never realized those strips were that important for proper playback speed,

[CEDatum]

If the turntable belt has not been replaced in a long time, replace it with an RCA belt part no 152751. And lubricate the turntable bearings when the turntable is removed from the player.
This belt has a critical spec and it is unlikely that an OEM belt will correct the color fade problem .
Replace the belt before attempting any major adjustments to the player.

[RT9342]

Hey, Losunge - I may be able to figure this out soon (I hope) - I just recently bought a Sears player (which has the same chassis as the Zenith) and it's doing the EXACT same thing! I noticed that if you gently put your thumb & index finger on the edges of the spindle while it's playing, it'll clear up after about 2 or 3 seconds and stay stable until you take your fingers off. Apparently it's either a bearing problem or the magnets, as Mario mentioned. I'm going to work hard to fix it and I'll let you know what's causing.