CED VideoDisc and Player Discussion

[martin]

My sjt 090 came to me with bad 5 volt regulator chip and a bad belt. Replaced those and a disc played OK but will not eject.
Stylus arm retracts to home position and stops with the led showing 2 horizontal lines.Disc is not raised to the removal location The 2 switches at the home location seem ok. Anyone have any suggestions? Thanks.
Martin

[Rixrex]

So the load belt motor is not being triggered to run, is that it?

Or does the load belt motor run but the disc lift gearing and stem not move?

[martin]

The belt on the function motor was replaced. I have the RCA service manual and they call it the function motor. The other motor is the stepper motor. I think what you call the loading is what I have called the function motor. It is the one at back left of unit. The disc will return to home position after playing the disc but stops there and the disc will oscillate back and forth about 2 inches at the rim bur nothing else happens. Play button has no effect, reject button has no effect. If I turn unit off and back on the unit resets and will play the disc again but not eject it. The process to raise disc up does not start. The disc oscillating seems to say the microprocessor has some bad data. The switches 10 and 11 at the home position seem to work OK. Ther may ba a timing problem somewhere but I have not worked on this type of equipment before. I hope my response is not much too long. Thanks for your response.
Martin

[Rixrex]

Right, what I called the load motor is the function motor.

I had a player that did this because the eject button was not working right, and ended up manually turning the gears to get the disc up and in position to then slide the caddy in. I did it like so:

1. Turn off power, and unplug.

2. Make sure the turntable is set so that the cutout that allows the transfer rod to pass through the turntable is in correct position above the transfer rod. This is most important for if not, you'll snap off the pivot that moves the transfer rod upward as the rod catches on the turntable.

3. Manually turn the gears so the rod moves up & lifts the disc into position so you can push in the caddy and get the disc out.

4. I then plugged in the player and let it cycle through on and off a few times to check that everything was in proper sync. All the time I was making sure the turntable was in proper position to allow the transfer rod to move up through it.

After I fixed that eject button, it worked fine.

[martin]

I got the disc out as you suggested. If I turn rhe gears to raise the disc and push in the sleeve and then plug the unit in with the sleeve inserted the unit will eject it with the disc normally. The front panel controls seem OK. the resistance when pad is pressed is about 190 ohms for each of the three buttons. the unit will play and if reject is press the arm retracts to home location as before and nothing will work and the 2 horizontal center segments of the LED are lit which probably indicates the micro is in a state of confusion. I now have another problem, The "L" never shows on th LED display now and the stepper oscillates back and forth a small amount when the unit on button is pressed . A disc will load and play and still not eject. Sure seems like a bad sensor or switch. Let me know if you have any suggestions.
Thanks for your help on this thing.
Martin

[martin]

I have the Sams manual and it states that the turntable will electronically seek the locked position so unloading can occur but no info about how the lock is sensed. The table on mine does not seem to be in that position. Do you have any info about that locking sequence? Thanks again.
Martin

[Rixrex]

You said you saw the turntable oscillating back and forth, correct? That's the turntable seeking the "locked" position, meaning the position where the cutout sits right over the transfer rod. Any other turntable position will cause the transfer rod to be blocked and cause the pivot to snap.

I think your troubles still have to do with the reject circuitry, or maybe a combination of that and those located at the switches that cycle the transfer rod sequence, or within their circuits. These are the two switches that cycle according to where the transfer rod pivot is situated. The transfer rod pivot has an extension on one side that acts as a finger to operate these two switches. That extension must be located below the transfer rod, not above, as sometimes happens if the pivot has been replaced incorrectly.

The machine upon initial turn on and showing dashes on the display, will cycle the pivot to the lower, back switch. This switch consists of two spring-metal strips that are pushed together by the pivot. Upon the pivot reaching lower switch, the display turns to L, and the disc can be loaded. If no disc is loaded and the power switched off, then the player cycles back to off position where the pivot is not touching either switch and the transfer rod is in a middle position.

If a disc is loaded, the pivot then leaves the lower switch, cycles upward to lift the disc via transfer rod, and then continues on over the high point of the main gear and back down to where is touches the higher, forward switch, and it's other end is now located under the turntable. This is a standard spring-loaded lever type switch that completes the circuit that stops the transfer rod, and frees the turntable to spin, and bring forward the stylus arm, etc. According to you, all this is happening, except perhaps no L is flashing. Typically no L flashes until the pivot contacts the lower, back switch.

The reject button (or the end of that disc side play) is responsible to break this disc play circuit, stop the turntable into locked position, and cause the cycling of the transfer rod back to it's highest point lifting the disc up to the unload position. This is the cycle you cannot get to.

When triggered, the cycle works because a spline is still in and pressing other switches and causes the player to run this sequence. If no spline was inside, then it would not know to lift the disc and stop and show UL, but would just continue back to the load position, which is what it does once the disc is removed.

It's quite a marvel of engineering and timing. If you can get ahold of a working SJT or SKT player for observation, you'd get a good idea of the cycling sequence and what switches do which operations. That might help you track down the trouble. Otherwise, it's a good parts player.

[ChateauxFaygeaux]

When the movie stops playing, do you see the turntable rocking loosely back an forth once it spins down?

I had an SJT100 refuse to eject a disk just like yours. I could load and play a disc, but when it came time to pull the disc out, I had to go through all sorts of contortions to get it to eject. I recall that after the turntable stopped, I could move it into the position it needed to be in for the transfer rod to poke through.

My problem turned out to be a defective turntable drive op amp. If you replaced a voltage regulator like you had said initially, this seems even more plausible. Because one of the phase outputs was missing, the player was unable to lock the turntable into a fixed position (such that the transfer rod could reach through the turntable and push the disk upwards), and as such it would never complete the eject sequence.

If you've nothing else better to try, I was able to test this pretty easily with a logic probe.

Here is the link to my repair notes (this site):

http://cedmagic.com/forum/viewtopic.php?t=103&highlight=

Edit: bad grammar (and I probably missed something else, too)

[martin]

Thanks for your response. The hunting problem is exactly what my unit does. If I reach in and stop it at the location allowing the hole to line up properly the disc will eject. I will locate the replacement I.C . and replace it. Thanks again. I will post the results of the chip change.

[martin]

Thanks for the information. It made sense to me but it did not work. The disc still hunts and will not reject. The voltages from the Hall devices to the micro seem OK.
As it hunts the voltages go up and down as expected. I accidentally shorted pins 21 and 22 and reject started at the wrong spot so I had to quickly kill power before anything broke. It seems unlikely that the mechanical micro is bad but who knows.
I used an ESR meter tyo test all electrolytic caps and they seem OK. This is my unit so do not spend a lot of time on but would be nice to get it working. Thanks.

[ChateauxFaygeaux]

[Rixrex]

I recall something similar happening once on a broken SJT 300 player I had.

The off microswitch located at the right rear (looking at front of player) that is activated (pressed to open a closed circuit) by a moving slider assembly when the player has no disc and is switched off, was not being pressed because the slider assembly catch pin had sheared, leaving it dangling somewhat.

This would then cause the player to never stop in unload position, but just keep rcycling through stopping, then reload and play. Before I realized that this switch was not being pressed, and in an effort to locate the trouble, while a disc was playing, I pushed with a small wood stick, the microswitch that is pressed when the player cycles to the load/unload position.

This caused the player to go immediately into an attempt to set the turntable to seek the correct position for lifting the disc, even though the actual lift did not occur, and then the disc oscillated as if trying to get the turntable slot right above the disc lift arm. I let off the microswitch and it stopped.

Basically, there were two microswitches being pressed simultaneously, opening two closed circuits that were never meant to be open at the same time, but were meant to be pressed independently of one another, keeping one circuit closed with the other open, and visa versa.