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CD player noise - braaap

StephenB

Pointy birds...........
Maybe someone can help resolve the above noise when I place a disc in my little dot CDP_III player

It’s a top loader with same mech as bel canto cd2 (Philips cdpro2 iirc)

once disc is initialised it’s fine, only when loading

Removed top plate a while ago but nothing loose or any grit on mech was obvious, hoping it might be a known issue and easily resolved

Audio quality is about to be directly compared to a bel canto cd3t, so if I decide to sell the little dot I’d like it to be at its healthiest
 
How is the CD clamped in place?
Is it simply that the clamp is slipping when the disc initially spins-up?

That's most likely to my mind, it;s the most violent speed change the disc/mech sees - after which it'd play fine.

Some CDs are produced down at the thin end of the Red book standard, and that, and perhaps age/wear on whatever is the clamping surface on the underside of the puck or whatever you have, could be all it is.

Simple test - cut a thin shim of something grippy, or thick paper/business card: put on the disc centred* and then load and see what happens.

(* if the mech is out of sight when it loads, add the merest dab of something wipe-offable and tacky to retain in place, so you don't loose the shim in the mech. I've also used short clippings from the sticky end of a post-it around the centre hole before now to test like this - might be all you need to try.)
 
I had a similar problem on a Marantz CD player - I followed Martin’s advice and it solved the problem.

Try putting a second disk on top of the first. If that cures it, you are in the same place I was!
 
I had a quick look again last night

the magnetic puck has no low friction element to it, nor does the support disc around the spindle, which makes slippage look like a possibility, I’ll see if any online pics show something around the spindle like an o-ring or similar that may have escaped.

I had dismissed a basic mechanical issue as it didn’t make this noise when new and my mind was led down a less mechanical and more electronic issue

I’ll take a vid and try and find a means of uploading it

thanks for the replies
 
stick them on dropbox in a zip archive and send a link via a conversation message to interested parties? I'd take a look, send me a PM :)
 
Very helpful! Seems to me it's coming from the sled, returning to centre before it tries to find focus and the sled drive is overrunning a little - sounds like the drive gear slipping on the rack. Perhaps the limit switch is tired/a little too far in toward the centre or something simple and mechanical (sled drive gear engagement, or the sled rails just need a clean because its a little gummed-up)

You'd have to get the mech free to look at the underside.
 
As per Martins comment - that definately sounds like the laser sled gears slipping as the sled hits the physical end stop. I'm not familiar with the CDPRO2 but the Philips VAM mechanisms have a little reed switch that the laser sled hits so it knows when it's at its inner position, if this reed switch is misaligned or duff the sled just keeps going off the end of the rack gear teeth and starts ratcheting just like yours does.
So it could be the inner limit switch, or maybe your gear teeth are just very worn, or something in the sled drive is loose.
And just because I happen to have a Philips VAM mechanism in front of me right now I dropped a quick video of what we think might be making the noise, I know its not the same as the CDPRO2 but they all work on basically the same principle.

https://www.dropbox.com/s/u4cwkzqtcjapkyj/IMG_1959.MOV?dl=0

Oh - and I wouldn't let it do it too much or you will chew up the plastic gear teeth :(
 
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Yep - you see laser vibrate in time to the braaap. Weird though - normally switch is already engaged with laser at that position, so it should go straight to focus/spin.

As above, could be misaligned or dirty switch - the braaap seems to activate the switch, otherwise it wouldn’t try and read TOC.

I suspect it has the same little switches as all the other worm drive VAM 12.x mechs. I’ve loads here with tired lasers, so take photos when you strip it down - I can send you an entire spare mech assuming gears and switches are the same.
 
I think as has been suggested it looks like the sled gear slipping.
The laser will return towards the start of the disc to read the table of contents. Underneath the sled at the spindle motor end will be a micro switch that tells the laser sled that it has reached its end stop. Some of those philips vam variants have adjustment slots for the worm/pinion position on the underside of the mech. Normally a White plastic toothed arrangement with adjustable holes wider than the screw head shoulder. This is designed for fine adjustment and the fact it is so probably means that on some mechs this was required?
The end stop switch could be faulty or just need a squirt of contact cleaner also?
My explanation is probably not describing the part clearly but if i can find a pic will add to this thread,

Regards Jim
 
stripped it down to access the limit switch

both ends of the rack look good and no gear debris to be seen, seems like the switch was not functioning or functioning intermittently and looked like some poor solder contact onto the ribbon

I did a clean of the contacts and prodded the solder a bit, but foolishly stuck it back together without doing a simple contact check hoping a light tweak on the contact to make it switch sooner would be enough

now the "braap" is constant and doesn't see the disc at all, so looks like we are in the correct area and will be going back in today with my meter and possibly soldering iron

unfortunately the switch mech is obscured by a ribbon cable passing over the top which means I need 3 hands

https://encosystems.net/instructions/cd-pro-with-opu1-cd-pro-1-vau-125210/

in pic 4 [right of centre along bottom ] the ribbon from the spindle passes over the switch mech


I could only see one company in Germany who offer repair and very limited spares on this mech, and TBH am thinking maybe I should try and locate someone in UK before I potentially scrap the mech :)
 
I think you’ll have problems finding a replacement mech - and silly to scrap it if it is only the switch. Shame you didn’t take a photo of the switch. All the spare mechs I have use the leaf switch you can see in the photo of the donor mech in the document you linked to on replacing just the laser unit (step 7).

I’m fairly sure a Primare CD20 or 21 I repaired also required me to swap the laser rather than the whole mech, and that mech, while not a PRo Version like yours, had a tiny micro switch to sense sled end stop. I imagine yours is similar.

Get a photo - someone here will be able to recommend a source for replacement :)
 
It certainly appears that you're on the right track but unfortunate it's now worse and not better!!!! A high resolution and well lit photo of the limit switch and its bits would be useful

If you figure it out yourself please let the forum know - we like success stories :)
 
Replacement Philips variants are available but they are not officially produced by philips anymore. They seem to come from the far east.
They are on ebay but buyer beware as quality is hit and miss.
I successfully repaired my naim cd5 with one a few years ago and its still working fine.
'new' units available that are OEM parts seemed to be refurbished units last time i checked, they are pricey but may come with some sort of warranty.
 
The contacts and operation of contact all checks out, so the sled appears to be functioning properly, I have found a UK repairer on eBay with good feedback who will replace the laser, service unit and 6 month warranty for just over £100

thinking this may be a safer option than me fixing it till it breaks :)
 


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