What causes radial error?

[Chivvyp]

Hi,

I used to have two working Marantz CD48 players

I attempted to fit a new external clock in one and then the cd wouldn't spin at all.

I then tried to fit the clock to my second CD48 with the same results.

Anyway, I gave up on that and refitted the original clock components (with a lot of point to point wiring due to lifted tracks). The outcome is that the disc now spins but doesn't read TOC. The self test mode gives radial error for both players (and with boards/mechanisms swapped).

The error diagnosis for rdial error all seems to be based around the drivers in the servo area but given that I've only played with the clock area of the board in both players it would seem more likely to me that the cause is related to the clock?

Anyone got any ideas, I don't really understand what a radial error relates to.

Regards

Pete

 

[Mooly]

Radial error means a problem with the "left/right" movement of the swing arm when tracking a disc. The error signa; is derived from the photo diode array in the pickup. On a normal pickup it would be called the tracking. If the disc spins at the correct speed then the focusing has to be OK.

I think you have to accept it is a man made problem and all you can do is carefully recheck all your work. Tha fact you have to identical players the same suggests you have made the same error on both. Maybe a component value is incorrect...

 

[Chivvyp]

Thanks mooly,

I'll go back over it at the weekend but I'm pretty sure I put the original clock components back correctly in each case, maybe something got damaged in the process, I checked the resistors were ok but there's a couple of 10/22 pf caps and my mm doesnt go that low.

When you talk about the swing arm, the mech is a 12.2, that would associate with the sledge moving in and out?

pete

 

[Mooly]

Usually the term "radial" usually crops up with the Philips swing arm pickups. They only have two variables, the up/down (focus) of the lens and the arm (radial). I've never associated the term to conventional pickups.

All I would say is don't look to deep... it has to be something you have done.

 

[Chivvyp]

My worry is that when I connected the external clock (that didn't work) I might have damaged the SAA7345 decoder chip.

 

[Rundmaus]

Usually the term "radial" usually crops up with the Philips swing arm pickups. They only have two variables, the up/down (focus) of the lens and the arm (radial). I've never associated the term to conventional pickups.

IMHO, the term 'radial' simply denotes the coordinate that is radial to the spinning disc. Could also be called 'tracking'. Any laser pickup has only these two variables: 'focus' moves the focus lens up/down, 'radial/tracking' moves the pickup assembly radially across the disc. I vaguely remember there are some more sophisticated pickups that can perform (limited) radial movements of the lens too, finer than moving the whole slide.

Rundmaus

EDIT: Back to topic: If you have access to a service manual, try to find out what possible reasons cause the unit to throw a 'radial' error. A first guess would be that it means the pickup does not respond to tracking commands in the way it should, so the tracking servo circuit fails to follow the track.

Does the pickup move at all, trying to read the TOC?

 

[PlasticIsGood]

Philips/Marantz mysterious model numbering. The 43 is in the same series as the 53 and 63.

The swing arm mech with its single beam system was sadly abandoned in favour of the universal "3-beam" system with sled and two-axis head. The beam is split to produce a main image and two side images. In normal operation, the difference in brightness between the two side images is used to generate an error signal which is used by the tracking system to centre the head on the disc track.

In normal operation the tracking system has this radial error as its analogue control input, and it has analogue outputs to a moving coil mechanism in the laser head for fine radial tracking, and to the sled for coarse tracking. As with a record player cartridge/arm, there are issues of bias and gain and unwanted resonance and noise, so it's a finely tuned circuit with dedicated chips. Other photodiodes, BTW, pick up the central image and their outputs are used by another chip for focus and data extraction.

The chip in your player responsible for radial error processing is the TDA1301T. Although the tracking process is analogue and self-contained in the chip in normal play mode, the system control chip must be able to intervene for stuff like start-up, track jumping and stopping. It appears that a serial interface is used for comms between the two chips.

Exactly where your error message comes from isn't documented in the service manual, but it might be in datasheets for the chips. The central processor is responsible for reporting the error.

Whatever, the serial interface needs a clock. I don't know how the various clocks are related, but the service manual should provide some clue.

Obviously you should check that all the connectors are secure, especially the one for the ribbon. If it has a locking collar make sure you have locked it after plugging the ribbon in.

 

[Chivvyp]

Philips/Marantz mysterious model numbering. The 43 is in the same series as the 53 and 63.

In this case the player is a Marantz CD48, Marantz version of Philips CD751. It has a CDM12 mech.

Rundmaus, according to the service manual the radial error relates to the servo circuit but given that the only part of the board that I touched is the decoder clock circuit it seems more likely to me that the cause of the error is there somewhere.

In the selftest mode 03 (radial test) with no disc loaded the pickup moves from rest at the centre to the outside.

In the selftest mode 03 (radial test) with a disc loaded the pickup doesn't move at all.

Regards

Pete

 

[Rundmaus]

According to the TDA1301T datasheet http://www.datasheetcatalog.org/datasheet/philips/TDA1301.pdf, the chip does not only manage all tracking/focus servo functions, but is also capable of generating the clock signal for other components.

So your assumption that tracking servo and clock circuit have no overlap might be wrong.

Rundmaus

 

[PlasticIsGood]

In this case the player is a Marantz CD48, Marantz version of Philips CD751. It has a CDM12 mech.

oops. Daft numbering system. Same laser mech though. Same or very similar chips I guess but I haven't seen the CD48 manual. Same principles of operation.

Rundmaus, according to the service manual the radial error relates to the servo circuit but given that the only part of the board that I touched is the decoder clock circuit it seems more likely to me that the cause of the error is there somewhere.

In the selftest mode 03 (radial test) with no disc loaded the pickup moves from rest at the centre to the outside.

In the selftest mode 03 (radial test) with a disc loaded the pickup doesn't move at all.

You know that the sled is able to move, but not necessarily in response to radial error. You can't tell with a disc in place whether the tracking motor inside the head is moving or not. Does the head not move to the centre start position with a disc in place?

 

[Chivvyp]

Hi,

Rundmaus, according to the schematics the 1301 has a seperate clock, it doesn't seem to take any input from the decoder clock.

Plasticisgood, the resting point for the sled seems to be at the centre, when loading a disc it doesn't seem to be moving from there. In test mode, with a disc in, I can get the sled to move to the outside with the advance button, releasing the button the sled goes back to centre. According to the test instructions this indicates it is ok.

The test details also give some resistance measurements to check across the plug sockets for the radial and sledge and these check out ok.

Given the above, I really think this does relate to the decoder clock circuit that I tried to mod but the replacement components seem to all check out (can't check the crystal or 2 very small caps 10/22pf) and the components all show continuity to each other and the decoder legs correctly

Pete