Denon DN-501C CD-player not reading CD

[PowerAmpFreak]

Hello, I have tried to see what could be the problem in this CD-player with no luck.
The service manual for Denon pro gear is hard to come by.
The player loads the CD, spin the disc, but instead of focus adjustment the sled itself is jumping a few millimeters, and tries about 5-6 times and shows "Media Error"
The CD-transport itself has a partnumber of TD-S208PR-6, not much of info able to find.
This can be a problem with the PCB itself, but most often the transport is the problem.

[redwire]

Re: Denon DN-501C CD-player not reading CD

The sled should move smoothly.
Commonly I find the transports need lubrication on the rails and worm-shaft. With oil and grease, they get too stiff and can jam/stick gears slip.
I use light grease on the rails and light oil the worm-shaft only if that matches the factory lube (oil vs. grease) there. It's a grease vs oil question. Clean off the old lube with IPA and Q-tips.
I would also check the sled home sensor switch is working, that the sled is not too far off in position.
I thought first step is to spin up the disc, then focus step and look for pulses from the CD pits. If it does not see anything, it must be moving the sled hunting.

[PowerAmpFreak]

Re: Denon DN-501C CD-player not reading CD

Thanks
I cleaned the sled with isopropanol there are no difference
The homeposition switch is measured ok

Here is a youtube vid of the problem:
https://youtu.be/HuLwPi6dgaE

[R_J]

Re: Denon DN-501C CD-player not reading CD

It is very likely the laser pickup has failed.

[PowerAmpFreak]

Re: Denon DN-501C CD-player not reading CD

Please tell how you came to that conclusion.
Cause the focus error is so big and pull the sled? Due to no signal from pickup?

[lotas]

Re: Denon DN-501C CD-player not reading CD

Check all microswitches (for a short circuit), these may be somewhere else.

[redwire]

Re: Denon DN-501C CD-player not reading CD

If the transport is hunting to see a CD, it can be a mechanical problem (sled too far in) and this has a belt drive for the worm shaft?
Or an electronic problem, you should find the factory testpoint for the pickup photo detector signal and use an oscilloscope to see if pulses are there. This would indicate the laser and focus servo are OK, data coming in but not the lead in. I think this player has a lot of circuitry in the transport.

The service manual might be here https://****************/load/audio/denon/279-4-2 but I don't have membership on the russian site. The URL gets blocked out here.
The middle main board says DN700C so the 501 may also be similar.

[lotas]

Re: Denon DN-501C CD-player not reading CD

ser. manual

[PowerAmpFreak]

Re: Denon DN-501C CD-player not reading CD

Thanks a lot. The service manual will help a lot. Thanks

[PowerAmpFreak]

Re: Denon DN-501C CD-player not reading CD

Thanks to the service manual I could measure the laser pickup was worn out. The current regulator showed a very much higher value than limit.
So a new pickup is ordered.

[PowerAmpFreak]

Re: Denon DN-501C CD-player not reading CD

Even after replacing the laser pickup (and desolder the ESD protection) the player behaves exactly the same.
During TOC read, there are ZERO output from the RF front-end chip. My question is what level the RF should be on the pick-out itself before the preamp, anyone knows ?
(Typically)

[PowerAmpFreak]

Re: Denon DN-501C CD-player not reading CD

I had the chance to try another cd drive from another Denon DN unit and that also does not work in this maschine
So it seems the fault is in the control board.
(The drive works in the other maschine)

[PowerAmpFreak]

Re: Denon DN-501C CD-player not reading CD

The original pickup has partnumber EP-HD870PB and I replaced it with SFHD870 after reading some info that it should be compatible, but does anyone know if this is true ?

[PowerAmpFreak]

Re: Denon DN-501C CD-player not reading CD

Finally solved. After some more troubleshooting the laser pickup flatcable was faulty, it had several broken strands.
After replacing the CD works nicely.