Why does my CDM4 skip?

[S.Spielbergo]

I have a 1990 Proton AC 620 (philips based) with tda1541a and it sounds great but the transport has this anoying habit of skipping every now and then even when I play flawless CDs. I recapped pretty much the whole pc board and cleaned the laser lens but the problem persists. Since I don't know what I'm doing I haven't played with the adjusting pots yet, any advice?

 

[stephensank]

While a cd is playing, lightly feel for a bumping vibration in the top middle of the disc clamper, on top of the spinning hub. If you feel bumping or excessive vibration, you'll just need to pull the clamping arm plate, pop out the clamper hub & then sand flat the surface of the clamping plate that contacts the ball bearing in the top of the hub, eliminating the dimple worn into it by the ball. Once flat, use the finest sandpaper to get a finely flat surface, add some semi-thick grease to it & reassemble. Should totally cure it.

 

[S.Spielbergo]

This unit had a severe case of the pitting you described, I ended up doing exactly what you mentioned during the lass rebuild session. Just discovered that my reduced clamping force is the culprit, inreased it and problem solved...knock on wood.

 

[Tino_diy]

Sorry,
I have some skipping problem with my CJ DV-2b cd player, which uses a Philips L1210/11 tray loader and VAM1201 (I replaced it trying to fix the skip bits problem) and have noted that the clamp bottom
base is not very flat. Maybe that also my problem is due to the clamp?

http://www.diyaudio.com/forums/showthread.php?s=&threadid=138237

If that can be the problem, is it possible to do what stephensank wrote also on the L1210/11 clamp? But I don't see how to unmount it...
Thanks,
Tino

 

[lu64319]

I suggest you to check lubricate on tracking mortor. Sometimes when the grease less will cause skip.

 

[Tino_diy]

Hi lu64319,
I have tried many times to lubricate the different mechanics (VAM1201, VAm1202) I replaced, but that never solved the problem. This week-end I replaced all the mechanic (including the tray loader, for the first time) with a old CD12.1 and apparently there are no more skips on bought CDs, but with the CD-R burned at more than 74'. Probably the problem was on the tray loader (clamp not leveled) and I will try to add a VAM1201/J on this new L1210/11 loader...
I will update my original post when I will sure of the solution.
Thanks for your interest.
Tino

 

[poynton]

I suggest you to check lubricate on tracking mortor. Sometimes when the grease less will cause skip.

Hi lu64319,
I have tried many times to lubricate the different mechanics (VAM1201, VAm1202) I replaced, but that never solved the problem. ..........

the grease on these mechs goes hard with age and causes tracking problems.

Clean ALL the old grease off including in the gears

NEVER REGREASE or LUBRICATE

Andy

 

[Pano]

So you mean to leave them dry - no new lube?

 

[Tino_diy]

In past, I have found some problem with grease, but never with oil (specific for mechanical gears).
In any case, also with a new mechanic not lubricated I still had skipping problems, so my real problem was the tray loader...
Ciao!

 

[poynton]

So you mean to leave them dry - no new lube?

yes.

If you want to use grease, there is usually enough on the side of your nose !

Andy

 

[acid_k2]

Clean old grease, then relube.

I use light oil (gun oil) for metallic rod and brass bushes, and white lithium grease (applied with a paintbrush) on plastic gears. All lubricant in small amount.

Check lubrication in motors bushes also. Clean it first with alchool or something similar. Dirt and grease (or oil) together are a ugly beast for parts in motion.

In my OnKyo, skipping was related to dirt and worn spindle motor.