STUDER A727 became pick on disc reading/tracking.

[yjwu412]

Hello:

I have a Studer A727. Recently it became picky on reading discs, either CD or CDR, especially after one hour's playing*mad*.

The power supply seemed to be O.K. I found the temperature of TDA1541, SAA7210 and SAA7220 were all pretty high! Was it normal? Adding block of heat sink did not improve the situcation much.
But why the laser pickup failed to keep track on the disc? Was it a laser servo problem? Chips on servo board were run at normal temperature.

Or the CDM-1 was running at final steam?

Is it possible to swap CDM-1 laser pickup from a working ReVox B225?
I know that the circuit boards on these two CDM-1 are different. Can we measure the pot. value responsible for laser power on each of the CDM-1 and exchange pot. setting. I think this way the laser might be kept at the same current during a circuit board swapping, provided the supply voltage was the same.

Thank you!

Y.-J. Wu

[Tinman]

OK, the CDM-0/1 almost NEVER goes bad.

I own several 727's and a B225.

These players need to be re-capped now. Measuring the caps is speculation against what we already know.

Do NOT swap out the CDM. It is 99% fine.

If you want to overhaul it, replace the capacitors on that board, take the spindle motor apart ( CDM-1 ONLY!! ) clean and re-lube it. Then adjust the grey screw on the bottom very carefully until it reads all discs again. This is normally done with an oscilloscope, but you can get pretty close by trying a few discs. The spindle height is CRUICAL for it to read the TOC on the CD on initial spin-up. What happens is that the bearing surface wears a dimple into it, lowering the spindle height and making it harder to turn.

Then I'd consider replacing at the very least the FRAKO branded capacitors, as they do tend to now suddenly dead-short.

This will in 99% of cases return the player to perfect running condition. Naturally, clean the lens while at it.

And just for fun....

[yjwu412]

Hello Tinman:

Wow! A massive collection of Studer-ReVox!

Thank you for your suggestion. I also heard that CDM-0/1 almost never fail. I had already adjusted the spindle height before. Not much improvement. I do have an osilloscope, but does this adjustment require a test CD?

So the high temperature operation of TDA1541, SAA7210, SAA7220 is normal? Why did they place those chips so close to regulated power supply heat sink? Do you suggest to re-cap the servo board first, decoder board next? And also the laser pick-up board?

My collection of Studer-ReVox took off about two years ago. 1st ReVox was a B77MkII, almost 20 years ago. Then came A77, high speed.

When I start eBaying the collection grows. My B780, B286, B225, Studer A725, ReVox C270, B215 and this A727 went next. I even got a pair of ReVox Studio 4 speakers.
This year marks another "Studer" era. I successfully repaired a A807, and recently a A810.

Best Regards,

Y.-J. Wu

[Warped Bezel]

An admirable collection! Willi would have smiled to hear your story.

[Tinman]

Hello Tinman:

Wow! A massive collection of Studer-ReVox!

Thank you for your suggestion. I also heard that CDM-0/1 almost never fail. I had already adjusted the spindle height before. Not much improvement. I do have an osilloscope, but does this adjustment require a test CD?

So the high temperature operation of TDA1541, SAA7210, SAA7220 is normal? Why did they place those chips so close to regulated power supply heat sink? Do you suggest to re-cap the servo board first, decoder board next? And also the laser pick-up board?

My collection of Studer-ReVox took off about two years ago. 1st ReVox was a B77MkII, almost 20 years ago. Then came A77, high speed.

When I start eBaying the collection grows. My B780, B286, B225, Studer A725, ReVox C270, B215 and this A727 went next. I even got a pair of ReVox Studio 4 speakers.
This year marks another "Studer" era. I successfully repaired a A807, and recently a A810.

Best Regards,

Y.-J. Wu

Yes, the chips run pretty warm. I re-cap the whole thing at once so I don't have to keep going back to it again and again. Just do one board at a time and test the player each time. Change out the silver can caps on the power supply first. I have found them to get problematic. If the rails aren't clean, the laser won't track well. Then pull the CDM, do what I suggested, and change out the few caps on that board. Re-test and see. The 727 is pretty solid, I doubt the whole thing needs a re-cap. The B225 usually does need it.

BTW, if you can, make a copy of the eprom. I have had one die on me already. Good thing I have a back up of the firmware. Burned a new chip and off it went again.

Marc

[tommygun]

OK, the CDM-0/1 almost NEVER goes bad.

I own several 727's and a B225.

These players need to be re-capped now. Measuring the caps is speculation against what we already know.

Do NOT swap out the CDM. It is 99% fine.

If you want to overhaul it, replace the capacitors on that board, take the spindle motor apart ( CDM-1 ONLY!! ) clean and re-lube it. Then adjust the grey screw on the bottom very carefully until it reads all discs again. This is normally done with an oscilloscope, but you can get pretty close by trying a few discs. The spindle height is CRUICAL for it to read the TOC on the CD on initial spin-up. What happens is that the bearing surface wears a dimple into it, lowering the spindle height and making it harder to turn.

Then I'd consider replacing at the very least the FRAKO branded capacitors, as they do tend to now suddenly dead-short.

This will in 99% of cases return the player to perfect running condition. Naturally, clean the lens while at it.

And just for fun....

Tinman, could you please tell me what DAC IC must be in Studer A727?
I've bought one, checked it and found 1541A (without S1 and crown.. )
Thank you