Philips Test Sample CD's

[ben12345]

Hi,

I'm trying to restore an old 1985 B&O Beogram CD50 CD Player.

The Service manual calls for 'Philips Test CD without Defects' or 'Sony YEDS5'

I can get access to Philips CD 3 or 5A, would either of these be any good?

Cheers,
Ben

 

[Mooly]

Any good disc is fine. You don't need any special discs for normal service work/alignment. Is there a particular problem with the unit, what pickup does it use ?
Regards Karl

 

[ben12345]

I went ahead and ordered the test sample 3 and 5 anyway. I found out that the disc 3 is the 'disc without defects' that the service manual calls for.

As far as the pickup, I havent got a clue!
I've found out that it uses a 3 beam laser system and the disk gets loaded upside down. Apparently its of Japanese origin, maybe Aiwa?

The problem was just a spindle motor in need of a little lube, but someone previously had messed with the pots on the servo PCB, so the machine isn't happy reading discs.

I can snap a pic of the guts if you think knowing the pickup type will help.

Thanks,
Ben

 

[Mooly]

Hi Ben, Do you have an oscilloscope, it's the only way to adjust/check any player. You have to be able to "see" the signal coming off the disc to correctly set up. You say someone has twiddled the pot's, that could be a problem and I think you need access to the service manual. Depending on the machine there may be adjustments for focus and tracking gain, EF balance and PLL lock. As a generalisation you can try this. If it will play at all, if you turn the focus gain up you may hear "white noise" coming from the optical pickup itself, adjust up to the point that the noise is apparant and then back off slightly. Tracking gain set initially to around mid point. EF balance is very critical, you certainly need scope for this. Try moving slightly each way and see if playability improves. PLL or phase locked loop again very critical, you need the set up procedure to adjust correctly and a frequency counter. You can set it to the midway between the points at which the player "loses it" assuming it is a pot for this adjustment (sometimes a coil, if it is don't touch). If you have a 'scope you may be suprised to see that the RF signal or eye patern coming off the disc always looks the same, it does not matter what the content of the disc is, the only exception is the "gap" between tracks tracks. Good luck
Regards Karl

 

[ben12345]

Hi,

Yes, I have an oscilloscope and the service manual. I think I also need a signal generator for setting up the spindle motor amplifier, but hopefully I can use my PC for that.

The Player does still play CD's, albeit with clicks and pops in the sound sometimes, and its slow to read the TOC and skip between tracks.

Maybe someone can shed some light onto the origin of the pickup.


Cheers,
Ben.

 

[Mooly]

You have cleaned the lens have'nt you. You need to put scope on the R.F. signal first to check it's quality and amplitude.

 

[Mooly]

What does that label say on the pickup, cant read it

 

[ben12345]

Hi,

Yes the lens has been cleaned. I can actually hear the white noise you mentioned when I play discs.

The label reads:

87-046-283-01
V301R02A04Q0

Cheers,
Ben

 

[Mooly]

Not familiar with that particular unit. First things first, A clean lens, and put scope on the RF signal. This tells all. Does the manual give an amplitude for this signal, usually about 1.2 volts PEAK TO PEAK on scope. Is the "diamond" shape clear when you expand the timebase on the scope.

 

[Mooly]

Is there a set up procedure in the manual for EF balance, this is critical adjustment. Needing a signal generator to set up the spindle motor implies a hall effect type motor. Dont think this is problem really, once playing the motor should not loose lock.

 

[ivoa]

Hi all,

I saw your discussion about B&O CD 50. I also have one and, although it is working, it needs a bit of cleaning and adjusting.

As for spindle motor, it is hall device, and as I read on Beomuse, it sometimes needs re lubrication. If anybody attemps to do this, be sure not to break coil ends as this is very tricky job.

What I would like to ask is about adjusting procedure - when you sad 'diamond' shape, on which oscillogram are you according at? Do you mean at RF signal after first amplification?

Ivo

 

[Mooly]

Hi,
The RF signal or eye pattern is the one to measure. It is the signal straight off the disc from the RF amplifier before it is applied to any of the digital processing stages. Unless a new optical unit has been fitted or it's had the pots turned it should not really need adjustment. If you do measure it be sure to use a correct ground for your 'scope. If you just use the case etc or "any" ground point this in itself can make the diamond shape look fuzzy. You really need a manual before you attempt adjustment. Is there any specific problem with the unit ?
Regards Karl

 

[ivoa]

Unit plays discs and read TOC. One problem is belt for cd draw and it seems a bit tricky to exchange since this unit has very interesting mechanical solution for drawer mechanisam. I would like to check other parameters, but I don't want to do it until I found service manual for it with proper alignment procedure. And yes, for PLL it uses coil!

Player works fine, but since it is about 25 years old, perhaps some adjustments should be done, or, at least, detail checking is recomended. I repair electronics for more than 20 years and 'gained my degree' on VCR's and hi-fi equipment.

Right now, I am looking for service manual with alignment checks/procedures.

I saw your discussion with Sony DAT problem and I posted my opinion there