Hi. So I picked up this player for $27 from the second hand store, mainly to see if it would work, and to tinker with it for the sake of practice. Like the title says, this LD-700 is having an issue with its optical laser hardware (not sure if that is the correct term btw, correct me if I'm off) getting jammed up in the track.

After removing the bonnet, what I see is the optical laser moving from starting postion (posterior of the case) towards the center of the disc and then it just gets stuck. Makes that awful whirring noise. The gears jump and the optical laser cannot move back, so it doesn't read the disc. I didn't want to completely disassemble the unit because I'm not sure what to look for here. Can anyone give me some pointers? I'm semi-comortable with hardware from building PC towers but this is a new area for me.

I believe the laser itself is still good and capable of reading discs, because the optical hardware doesn't move when I press play with no disc in the tray. The lights on the front of the player also seem to indicate that it correctly detects when a disc is inside or not.

Also want to add another issue that maybe simpler: When I got the unit, originally I couldn't get the tray to open up (it jammed and whirred). What I found is that I could only get it open by either turning the player on its side, or by manually lifting the clamp bar (?) that is used to secure the disc. The player acts like the tray is too heavy. I got it to open up by itself, correctly, a couple of times after manually assisted opening, not sure why it did that. Is this indicative of the rubber belt thing that is on the gears needing to be replaced, or is that something else?

I am aware as well that the LD-700 isn't a particularly special model. I already have nicer (and working) players so I don't need this unit as a main or anything. I just want to try and save the player and get some experience diagnosing/repairing a malfunctioning LD player.

I have some videos but I can't upload them here so I'll try to add them on an external link.

Thanks for reading

The tray problem sounds like the easy bit, definitely a new belt is the first thing to try. From another thread here:

Just to round things off, the 39.5mm inside diameter, 1.5mm square section belt arrived and seems a good fit, snug but not too tight.

(although that was me about a belt for the similar LD-V6100, so I think it's the right size but don't get cross with me if it's not!).

The laser movement sounds a bit more of a challenge, and it sounds like a physical problem so there's probably no choice but to disassemble it until you find what's causing the jam.

You've found the service manual on here? It does look pretty complicated but as long as you're careful and do everything step-by-step, maybe making notes as you go along, it won't be too bad. Make sure you take notice of the bit about the Potentiometer Pinion gear, I didn't when I first reassembled mine!

It's just a thought, probably wrong, but is the Transit screw (on the underside) unscrewed and loose? Just thinking, if someone had tightened that up when the laser carriage was in the wrong place, or if it's wedged in somehow, it might have this effect if the carriage hits it. It should have a spring around it so when unscrewed it stays captive in the player, but is pushed away from the carriage.

Good luck anyway, people are a bit sneery about the LD-700 on here but when I was a nipper it was my 'dream' player!

Alrighty then, when I get the chance (probably the weekend) I'll see about doing a disassembly, and will post some videos as I go. It might help me to know which players have the most similar guts, because I didn't find many posts about the LD-700. I can see it's just a basic little player so I'm not surprised few people would bother with them. I actually found some people saying they're not worth saving, but those posts were also 10+ years old when the good LD players were easier to come by. In my case I want to work on it for the shiggles without the guilt of doing the wrong thing on an actual prized LD player.

Will try to get a video of the optical device and post that before I get too involved. Also I did see the transit screw when I got it, but that wasn't it.

Could be something that is broken inside, or whatever. When I originally took the bonnet off, it did look like the previous owner had opened it to maybe mess with the tray. They left greasy fingerprints everywhere inside the bonnet, but they didn't really fix anything. (probably why it was dumped at the second hand store.) I suspect there may be some tiny part somewhere missing from that person's attempt, but I'll really have to go over the technical diagram with a fine tooth comb to be sure. The clamp that holds the disc down looked like it might be missing a spring on one side, not sure.

I appreciate the confirmation about the belt for the disc tray, so I'll give that a shot, too.

I realize that this answer is coming much later, but the technical solution is not exactly a simple one. And this issue will come up again if someone wants to get an older player up and running that has a laser pickup that is guided by a pinion potentiometer. Which is responsible for setting inner and outer disc limits.

In these older players, the path of the laser assembly is set using a potentiometer that is directly connected to the motor that drives the movements of the optics that reads the disc. There is a specific point in the movement of the potentiometer gear that delivers the signal to turn off the optics motor.

With time, this essential starting position can mechanically drift to a location that is beyond the barrier of possible motion for the gear system. It will therefore hit that barrier, and then continue to try to run indefinitely, making a banging sound.

The solution is that the inner disc position must be reset. First, that specific motor cut-off signal needs to be dialed back to a position that is behind the barrier. On LD-9200D, I accomplished this by gently decoupling the pinion gear teeth from the plastic track with a flat head screwdriver lifting up an adjacent part of the gear system. Turning the pinion gear counterclockwise, while decoupled from the gear system, has the effect of dialing back the inner disc cut-off signal. I aimed to get it to stop before hitting the plastic wall.

The next step is to further refine the position of where the laser assembly stops after pressing the power button. It is ideally supposed to stop directly where the lens needs to be in order to successfully recognize that a laserdisc has been loaded. I also had a closely related model (LD-8200D), which I used as a side by side point of comparison. I measured the distance from the outer edge of the top of the spindle grip to the center of the lens. It was a specific value in the working player, let's say 6.5 cm. I set the inner disc limit to have about the same measurement. This would bring the inner disc limit setting to a position at least much closer to where it needs to be in order to read a disc.

Fine adjustment of the inner disc position is set using a specific variable resistor on the main circuit board, as described in the service manual. There is also instructions to turn the variable resistor all the way to one side, so that you will have the entire range of motion to work with. You are moving that position gradually by tiny increments. In the absense of a test disc, I did a sample 12 inch laserdisc spin up with each successive turn of the variable resistor. Once it reached almost the correct position, it could read a disc for the first time. A bit more fine tuning is required using different discs, including CAV sides. Eventually it could read any disc that my other calibrated players could read, including 8 inch LD Singles with the use of the adapter.

It is not an easy process, but it is possible. The specific Japanese market model that I imported tends to be sold in the "junk" category because it often will need this kind of adjustment in order to work. I have been using it to play all kinds of discs for 1 year, and it doesn't miss a beat.