Philips test disc 5

[alanworland]

Just got myself an early Quad 66 cd player which seems to perform very well.
Internal examination shows at least one leaky electrolytic capacitor so an order has been placed for some long life replacements.
I have all the service information for this which describes dismantling and electrical setup very well.
It describes setting up laser current and focus adjustments using a Philips test disc 5?
Can't find any info on this at all let alone get hold of one, any ideas what's on it or where I could get one?

Alan

[Sideband]

From what I can remember when we had these at Philips it consists of a disc with deliberate and precise errors. It has strategically placed errors and drop-outs and simulated thumb prints in areas that are likely to cause a player to skip or stick. The idea being that a correctly adjusted player would be able to play the disc without any noticeable errors. They were expensive......around £100 back in the day. It was listed as a 'precision' test disc. I think there were several of these 'precision' discs for test and setting up purposes in the early days of CD's.

In the absence of one of these discs I think all you can do is either leave it as it is (assuming the laser has not been replaced) or set it up on a less than perfect CD. I doubt you will find one of these discs now but it might be worth looking on eBay Germany or Holland.

[Mooly]

Although I'm not familiar with the Quad player, the main problem with all these Philips based players is deterioration of the small electrolytics, particularly those on the servo boards. You must replace them all.

Manufacturer issued tests discs are normally discs produced to a known standard (reflectivity, error rate, eccentricity, thickness etc) and may also include discs with known reproducible errors as mentioned above.

Like so many things 'Philips', the alignment of the radial pickups were unique in that the laser power was adjusted by reference to the current produced in the photo diode array... and tbh few ever used this method.

Firstly the laser power is controlled by a closed loop servo and there is no reason to suppose it has altered as such. If the emission of the diode falls, the current is automatically increased.

I would advise just looking at the RF on the scope when playing a good Red Book standard disc (any commercial CD)and confirming it is within 1.2 to 1.5 volts peak to peak. Try a few discs and ensure that all fall within a narrow spread of amplitude and discard (for test purposes) any individual disc that is obviously low in amplitude compared to the majority.

Focus can be adjusted for best amplitude/clarity of the diamond pattern within the RF signal.

[alanworland]

Thanks for the information, I must say that I had drawn a blank with the test cd although I would have thought a 'modern' version of this would have been available?
I have just been through circuit diagrams and updated my order for caps!

Alan

[Sideband]

It probably isn't worth producing these discs any more. Most modern CD players use complete replacement modules which are factory adjusted. It's a far cry from the early players where the actual laser was replaced and then had to be aligned.

[Sideband]

If you look on eBay.de (Germany) and search for test CD you will find some but I doubt that they are for diagnostics. They are more for testing the operation of the CD but don't have simulated thumb prints and dropouts for setting up. Still worth browsing though. Sometimes an actual proper test disc does turn up.

[Mooly]

Close up of my Philips SBC444A Playability Disc.

The dark rectangle isn't clear in the picture but is a "simulated finger print" and is a grid of fine horizontal lines. The light wedge is "interruption in information layer. and consists of 7 tracks ranging from 400 to 1000 micrometer in size.

Black dots are 300,500,600,800 micrometer in size. Any player should be able to play the 400m/m interuption, the 300m/m dot and the simulated finger print.

My old Micromega with a CDM12.4/05 would play all with no audible errors, but you could hear the servo working overtime on the more severe tests.

[Sideband]

....long time since I've seen one of those!!

[alanworland]

I suppose without any sort of test disc I could always introduce some fingerprints!

Alan

[emeritus]

I recall an open university programme on mathematics about error correction demonstrating that a CD with four radial slots cut in it, played perfectly.