Studer A727/Revox B226 laser adjustable? where?

[cihuang]

Hello everyone,

I've an old Studer A727 which has great sound and so musical. But recently it begins to act strange. It won't play some CDs which were ok before. While the other CDs play well.

I've opened the case to see what happens. When playing the problematic CD the laser pickup (len) will float to the edge of CD and make z~~~~ noise, after few seconds the CD stops spinning and machine also stops. Eject the CD and retry then everything repeats again. However those CDs run well will run in 2 second, pretty annoying to me.

I have also dug out the whole forum and learned about there might be 3 adjustable parts which are focus gain, focus offset and laser output. I also found there's a CDM1 pcb scheme to show where they are. But no luck at all, the Studer pcb is not the same as I found. Are those adjustable to my Studer?

Anyone could help? I know there might be some problems regarding to the optical pickup of CDM1 since the age. But the machine has accompanied with me for a long time and brought me a lot of fun, I hope I can do something to make it live longer, and of course another reason is CDM1 is so hard to find a stock.

Really appreciated for all reply.

[Netlist]

Did you clean the lens?
This should be the first thing to do.
Here is a service manual.

/Hugo

[cihuang]

Thanks for reply.

Yes I did clean the len but no help. And I've tried to lubricate the bearing, looks like getting better and better.

Reading documents now, German is quite a challenge for me.

[Netlist]

If you have a scope you could measure the RF signal.
This should be close to what the manual defines.

/Hugo

[Lourens]

Originally posted by cihuang
I have also dug out the whole forum and learned about there might be 3 adjustable parts which are focus gain, focus offset and laser output.

If the laser is dying (?), you better replace the cdm1. It's really very easy with your A727. Find an old Philips cdp with a good working cdm1 (and check for the yellow G sticker on the Hall motor!), swap the drive boards, et voilá. Search eBay or the local fleamarket, forget stock replacements

Originally posted by cihuang
And I've tried to lubricate the bearing, looks like getting better and better.

What bearing? Quote: "The mechanism is equipped with self-lubricating bearings that require no maintenance" (service manual).

Originally posted by Netlist
If you have a scope you could measure the RF signal.
This should be close to what the manual defines.

You also need Test CD #3. Hard to get....
Any idea what what kind of signal track 1 contains, Hugo?

Lourens

[Steerpike]

It might be the L272 (IC in the B226) op amp chip. Gives symptoms like a faulty laser.

[JKoch]

Hi Netlist

In "Studer A727/Revox B226 laser adjustable? where?" thread (post #2 dated on 24-02-2005) you included link to Service Manual but this link is not working. Please, send me the Service Manual or the link to my account: jk@ai.pl. I can buy the machine and first I want collect more information about it.

Thanks

JKoch

[Netlist]

JKoch,
Do have a look here.
This is Studer's official ftp site.

/Hugo

[JKoch]

Thank you, Netlist.