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-   -   CDM 9 and servo circuit experts? (http://www.diyaudio.com/forums/digital-source/54171-cdm-9-servo-circuit-experts.html)

tubenut 25th March 2005 01:49 AM

CDM 9 and servo circuit experts?
 
Hi all

I am trying to sort a PS Audio Lambda Drive (CD transport). It was made for PS by Theta and is the same as their Data Basic (which I own as well).
These units use CDM9/60 (CDM9 pro iow). I have swapped optics on a few of these mechs from new CDM9/44 to sort them out. This unit is stumping me though.
When loading a disk the unit does its initial focus procedure and then starts spinning the disk to try and read TOC but 9 out of 10 times it fails and just end up speeding up and spinning for about 10 seconds or so until it gives up reading and gives an error on the display and goes blank or it just keeps spinning indefinitely. I t does seem to lock on the 8 cm CD icon.
The player has 3 “modules”. The loader has its own PCB which looks like it is Philips made with a TDA8808, JRC 4560 the TCA3702 or something I think. There is an unregulated PSU board (Theta) and then the main PCB (Theta) with the clock circuits and outputs, the SAA7310 another JRC 4560 near the CDM input and 037DPI as well as the TDA8809. The CDM and its loader PCB are now working as swapping this module into my working theta disks are read without a problem. I have also swapped the PSU boards and this made no difference. I am thus convinced the fault is on the main PCB…. But where to start? I have checked the 13 or so regulators on this board and they appear OK.

Any ideas anyone?

hacknet 25th March 2005 03:05 AM

is it possible that some sort of laser "biasing" is required? i remember hearing bout such stories awhile back with cdm4 lens.

tubenut 25th March 2005 06:27 AM

CDM 9 has no focus offset or current adjustment
 
it is all done "by itself" in the servo cct I believe. IE, there are no pots to adjust....

tubenut 29th March 2005 07:44 AM

In my post above I forgot to mention that although it has read TOC a few imes, it never actually played the disc.

Could this be a fault with the SAA7310? I have fitted another TDA8809 already but this made no diff. The TDA8809 was salvaged from another scrap player so I am not + it was OK but there was no change in the behaviour of the player.

Would the player achieve its focus to try and read TOC if the 8809 is faulty?

Thanks all

anatech 30th March 2005 01:19 AM

Hi tubenut,
Normally there is a test mode so you can activate one servo at a time. It would be very helpful to look at the RF "eye pattern". This is like a blood sample from you to a doctor.
-Chris

tubenut 30th March 2005 05:06 AM

On which pins of this chipset will I find the eye pattern?
Does anyone have a CDM9 philips player service manual. Like a CD930?

anatech 31st March 2005 12:53 AM

Hi tubenut,
Just poke around the first chip with a 'scope. The waveform is best viewed at 0.5uS / div and 0.5V / div. Expect around 1~1.5 Vp-p. There may be a filter with a couple small caps and a resistor near the chip.
By the first chip, I mean the chip that goes to the PU head flat connector. Not the coil drivers.
-Chris

tubenut 31st March 2005 05:52 AM

Quote:

The loader has its own PCB which looks like it is Philips made with a TDA8808, JRC 4560 the TCA3702 or something I think
Is the first chip not the TDA8808? In that case that is fine as swapping the loader module and PCB into my working Theta shows the laser/loader/PCB is fine.....

I will try and scope the beast around the weekend....

Thanks

anatech 1st April 2005 12:53 AM

Hi tubenut,
If the board is what I think it is, look for TDA1300. Poke around pins 9 & 10 for the RF pattern. This feeds pins 1 & 2 on the SAA7327H. This is a Chinese (yahoo) made PCB for which there is no service info from my sources.

-Chris


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