Hi Martin!

I removed and cleaned the threaded rod with a degreaser and a toothbrush then I put everything back in place and the arm does move a little further(about 2 mm)but I still have the problem.I decided to try the same experiment with the arm removed leaving only the threaded rod.The result is the same so the carriage is not dragging.By the way,I did try to remove the belt as you said and the motor does run but very slowly and weakly.

I checked the voltage on the tangential motor and when I press PLAY,it is 8,2volts.Is it enough? I'm thinking of trying some other belt size althought it seems adequate just to see the effect.

I'm not giving up!

Bye and thanks!

chris.

wongss; Sounds like the optical tracking sensor (at the base of the carriage) is faulty, probably a burned lamp - or the interrupter is badly adjusted.

chrisbou; Sounds like you are closing in on the problem. The voltage seems fine and the slow rotation of the motor to get the carriage to the exact drop spot is correct, we just have to get the threaded rod to follow the slow rotation which is where seized up things turn up. Take out the rod and clean at both ends where it rests in its plastic holders. Dust off the opto elements while in there.

Martin

Hi Chris 

Never give up, all it takes is lots of time!!  I have checked the voltage on the motor when it is going to the start position and it seems to be between 8 and 9volts.  Looks as if your motor is doing its job.  So if you are happy that the initial park position is OK and the motor is able to reach the correct speed, it might be time to look at the setup of the pulse counter.  Is your fully intact? I had a problem where the plastic arm was cracked and this left the board floating quite a lot.  I had to make a spring arm to keep it in its proper position.

Keep at it

Geoff 

Hi!

Is the optical tracking sensor the one that detects the small movement of the needle at the base of the carriage?If so,when I made the arm drop by putting 5 volts on the coil,the arm motor was running slowly and doing what it is suppose to do.The light works fine.It's funny that the carriage would advance slowly if I make the arm drop but refuses to do so after the initial few seconds when it reaches the disc. 

As for the rod,I have cleaned up everything including both ends.I still didn't put the carriage back on the rod.I wan't it to be free wheeling and the rod is very easy to turn with no drag at all but I still have the problem.I didn't get a chance to try a new belt yet but I plan to do so tomorrow.

And yes Geoff,everything is fully intact.I did inspect the underside of the carriage to check for cracks or anything odd but everything is perfectly fine.

chris

Dear Martin,

 The lamp is working....

Hello!

I changed the belt and there are some improvements.The carriage now reaches the disc exactly where it should but then,it starts to very slowly back up about a millimeter or two and the arm doesn't want to drop even if I make it travel to the middle of the disc.No clicks either.Should I put some grease on the threaded rod also?I put some on each end.

thanks again for all your support.

Chris

Hi Chris

Glad to hear that you are making progress.  The manual asks you to put some lubricant at five spots on the spindle and the in their case, they seem to use a mixture of two products to develop an oily consistency.  Since I have no experience with the lubricants that they quote, I simple put a drop of light machine oil at a few places down the spindle and it seems to work OK.  Others may have a different idea.

Does the motor actually go into reverse when the arm backs up or is it just releasing some compression in the system?  When it reaches the park position over the disc, are you getting any change in the coil voltage at all?

Geoff

Hi Geoff

Yes,the motor goes into reverse very slowly and when it stops,there is no change in the coil voltage.It takes about 30 seconds for the arm to back up at total stop.

I'll try lubricating at the other point see what it does.

I'll keep you posted!

thanks again

chris

Check the adjustments of the << and >> keys. It's mentioned in the service manual and is just about the only thing that can cause this fault.

Martin

I CAN'T BELIEVE IT! IT WORKS!!

Thank you again for all your support.I've been repairing electronics for twenty years but I have to say that I never could have don this without you.🤩

If you have time,I wish you can explain to me why the adjustment of the keys solved the last problem.I know the belt and the cleaning of the rod cured a part of it but the adjustment would not have been one of my choices for sure.

thanks again Martin & Geoff

chris