CDM-4/19 running at warpspeed

[Pharao.Pharao]

Hi,

the CDM-4/19 of my Philips CD780/00R player runs at warm speed when I turn on the power switch of the player. Since I don´t have any service manual neither of the player itself nor of the CDM-4/19, can anybody here please advise where and how to start debugging?

Thanks a mil in advance!
P.

 

[Audiofanatic]

Philips

Hi P,


If there is a SAA7220 or a SAA7345 in the player, than probably this is the culprit of the spinning CD.


Best regards,


Audiofanatic 😉

 

[Pharao.Pharao]

Hi there,

there is a SAA7220P/A and a SAA7210P in the player... . How to best diagnose whether the SAA7220P/A is the culprit one for the warp speed? I mean, I have just the datasheet of the SAA7220 in front of me and am looking for best practice diagnosis.

Thanks a mil again,
P.

 

[SY]

From my digital guru:

"Tell this guy to check the '7220 for proper operation. It has the clock,
and if that chip does not work, the platter spins at warp speed."

 

[electronic]

Look first at the TCA0372. If this are blown/shorted the CD will spin non stop.

 

[Mooly]

Check ALL supplies first to all I/C,s. Might be a safety resistor gone high.

 

[Pharao.Pharao]

@Mooly: All supplies to all ICs look good. I am just done with measuring. Even all resistors look OK to me.

@Predator864: There is a TCA0372DP2 (Motorola) on the board. I even have the datasheet and started measuring. Hmm.. question: Would the CD spin counter-clockwise at overspeed when this TCA0372DP2 is blown/shorted?

@SY: The SAA7220 is absolutely OK from what I measured. And the SAA7110 shows a fixed 88.19 kHz signal on Pin 17 (MSC). This is good news, right?

@All: If anybody could share the Service Manual for the Philips CD780/00R with me, I could continue much more systematically. Your help is highly appreciated!

Any more hints on how to continue a bit more systematically? I would like to track down the 88.19 kHz signal from Pin 17 (MSC) of the SAA7220 a bit further, but I don´t have any schematic of the PCB of the CD player, so I am a bit lost at this moment. Any advice you could give, please?

 

[electronic]

I blown a TCA0372 while measuring it. Then the CD began spinning like a madman.

 

[Pharao.Pharao]

@Predator864: Did the CD start spinning counter-clockwise after the TCA0372 was blown?

 

[electronic]

I dont know. Scared the crap out of me and unplugged it immediately.
I can clearly remember by shorting two pins of the IC the CD would spin in a direction, but again I dont know if it is CW or CCW.

 

[Pharao.Pharao]

Ok, thanks, Predator864. I have just ordered the service manual for the CD780/00R, but I am still missing a service manual for the CDM-4/19 drive. Anyone here willing to share it with me? Thanks in advance.

 

[electronic]

The CD Player Service Manual also contains the CDM4 diagnostics.

 

[Pharao.Pharao]

Ok, thanks for this info!

 

[Pharao.Pharao]

Meanwhile I believe it would be best to start measuring at the flexband where it connects to the main PCB of the player. The reason for my assumption is that the V_DD of the TCA0372 drops from 5.6V to 4.5V whenever I connect the flexband of the CDM-4/19 to the main PCB. No good sign I believe.

Well, does anyone here own a service manual for the CDM-4/19 which he/she can share with me, please? I think it only makes sense continue measuring when I have understood how the speed control mechanism of the CDM-4/19 actually works. I mean, since the spindle motor is only connected with 2 wires, I assume the laser recognizes the RPM of the turntable and sends back that "tachometer" signal to the main PCB. And, to further understand that mechanism, a service manual for the CDM-4/19 would suit best now. Can anyone share, please? The service manual for the whole player (CD780/00R from Philips) is already ordered by me, but no service manual for the CDM-4/19 was available. And I assume Philips will not fully cover the CDM-4/19 in the service manual of the CD780/00R.

Thanks m8s for your help,
P.