Denon DCD-1520 tray won't close DESPITE new belts

[RallyGuyToo]

Hi all,

I'm trying to get an old DCD-1520 running again. The player powers up fine. The tray was moving slowly and would not close - so I ordered new belts and installed them. The drawer STILL won't close all the way. Everything is clean and lubed. I have to push it with a good bit of force to get it to close. If I do that - the disc will be read and plays fine. However - in this state - when I push the open/close button - the play will NOT open the drawer, but rather stops the disc momentarily - then restarts it. It seems there's some logic that is sensing that the player has indeed opened and closed, but it hasn't. The only way to get the drawer to open when it's closed is to push on the white tab that's part of the motor mounting bracket (the white plastic motor carrier assembly) from the side where the guide rail is. If I do this - the drawer will open.

I took the entire transport out of the player and examined it. There are a couple cracks in the black plastic bits on the bottom of the tray - but they don't seem to be allowing any unusual play nor getting in the way to the drawer's travel.

What DOES work is to hold the tray slightly to the left as it travels closed. If I do that (holding the tray with a finger from underneath and "biasing" it to the left as it travels) - it closes all the way and the disc plays! I've read all the Denon DCD threads I could find - and there's no mention of this as a problem - or any suggestion of a fix. "CD alignment" searches just get laser alignment guidance - which I don't need. I can't find any bolts or screws that allow any play in the assembly.

Any suggestions on what might be going on here?

Thanks in advance - this is a great sounding player and I don't want to give up on it.

RK

 

[RallyGuyToo]

Okay - so here's an update already. I said "cleaned and lubed" - but it appears that it wasn't cleaned and lubed ENOUGH! I went through the whole mechanism carefully applying molykote 33 light (yeah, the good stuff) paying special attention to the tray that moves up and down within the drawer. I also replaced the new lower belt with the OLD belt. All of those changes fixed it. Interestingly - the NEW lower belt DID NOT WORK. It fit but seemed to exacerbate the loading problem. I swapped the belts back and forth several times to confirm this and the new belt always caused a loading problem while the old belt allowed the drawer to function properly. Unfortunate and I'm not sure why that happens. The upper new belt seems to have help the reliability of the drawer mechanism - but now that a full lubrication pass has the drawer working much more consistently - I wonder if that was the problem all along and I didn't need belts at all?

In any case - it seems to be working almost perfectly. But I'm happy to hear of anyone's suggestions about this problem or similar experiences with tray mechanisms.

RK

PS. Now that it's playing - it really is a marvelous player. A bit analytical, but heaps of detail and refinement. Glad it's back in rotation.

 

[drp1003]

One thing to add...

Your local hardware store in the plumbing section (ACE Hardware for example) sells rubber O-rings in various thicknesses and diameters. There are two main thicknesses, and If I can remember correctly, 3/16 in thickness of the o-ring itself is the size that works best for replacement CD player belts, All you have to do then is experiment with the overall diameter - or size - that matches your original belt size. Get one that is a tad bit undersized and get one that is very close to the same size. Don't go too small, because then there might be issues with putting too much strain on the tiny DC motor.

These o-rings are round. It's true. Not square. But I have been using them for years now with great success. They work great and are readily available. You don't have to order one and wait and pay a ton on shipping and all that crap.

Also, you can still find lasers for this model but they are not cheap, unfortunately.

 

[RallyGuyToo]

That's a great tip! The belt procurement process was actually not to painful - but I much prefer the "buy local" option. And I can't imagine that round vs square matter much for this application - but would be happy to hear from others if there is some compelling reason for square belts in these devices.

With the drawer now working properly - I'm on to the NEXT problem - with is poor tracking. It's skipping a bit and won't select tracks backwards. I've be able to make small improvements with some FO and FG tweaking - but I don't have a scope (yet) and so can't get it perfect. I've been looking for a detailed descrption of how to do this process for the 1520 and can't find one. There's a very frustrating video on Youtube where a guy shows the RESULTS of his efforts - but hadn't recorded the process!

Assuming I do have a dual-channel scope (I'm going to borrow one from an EE pal) - is there a resource anyone recommends for dialing in a CD player with the full gamut of adjustability (TG, TO, FG, FO, PLL)? Also - there's ANOTHER VR in the board "Slide" which I don't understand. What does that one do?

RK

 

[kwayde]

I use a DCD 1520 in the garage. A friend bought one that had problems so he had me look it over. Found the plastic parts that hold the suspension springs had disintegrated into tiny bits.
Another problem this deck has is where the output RCA jacks are directly soldered to the circuit board. After cables have been placed/removed multiple times the solder connections break at the circuit board.

I got my friend's deck going by cutting an old Bic pen apart to the correct length, see last pic. This wouldn't play discs that were home recorded.

 

[Sansuiman]

@kwayde, very nice using the plastic barrel of an old pen like that. I'll be filing that tidbit away for future use, as I continue to work on vintage CD players.

 

[kwayde]

@kwayde, very nice using the plastic barrel of an old pen like that. I'll be filing that tidbit away for future use, as I continue to work on vintage CD players.

The black pieces that disintegrated were like small cups that supported the springs. I couldn't find anything that was cup-like so I used the pen pieces which fastened things down rigidly. It worked well enough.

 

[dr*audio]

One thing to add...

Your local hardware store in the plumbing section (ACE Hardware for example) sells rubber O-rings in various thicknesses and diameters. There are two main thicknesses, and If I can remember correctly, 3/16 in thickness of the o-ring itself is the size that works best for replacement CD player belts, All you have to do then is experiment with the overall diameter - or size - that matches your original belt size. Get one that is a tad bit undersized and get one that is very close to the same size. Don't go too small, because then there might be issues with putting too much strain on the tiny DC motor.

These o-rings are round. It's true. Not square. But I have been using them for years now with great success. They work great and are readily available. You don't have to order one and wait and pay a ton on shipping and all that crap.

Also, you can still find lasers for this model but they are not cheap, unfortunately.

This is actually bad advice because the o rings are not stretchy enough and put too much load on the motor. If you can find an o ring that is the right circumference but thinner than the original belt it might work. The belts are available so there is really no reason to do this. www.vintage-electronics.net has good quality belts. One belt you need is SCB4.2. I can't find a replacement part number for the other one. You can measure it and go to www.vintage-electronics.net and search the square belts for one that is 10% smaller circumference than the original, but same cross section (thickness.)

 

[RallyGuyToo]

FWIW - I found these on AliExpress. Price was fair and delivery was surprisingly quick and cheap (compared to the insane and slow shipping we experience with Alibaba for parts for our business)

"New Tray Belt For Denon Belts DCD-1420 DCD-1500II DCD-1520 DCD-1560 2560 3520 3560 CD Audio Rubber Square Belt Set" from KMX Tech, whoever they are. ; )

The upper belt fits perfectly.

The lower belt's impact is a mystery to me. It fits perfectly and eliminates a bit of slippage I can see occur with the old stock belt. HOWEVER - the drawer operates LESS WELL with the new belt! The drawer won't operate at all with the new belt unless I push on the white motor subframe assembly, possibly removing some tension from the system? Is there a torque sensing circuit that is preventing the motor from running because the new belt is too tight?