PROGRESS on CD-ROM² Repair

[deubeul]

I can't tell, i never measured the voltage at the plots, only the resistance.
I'll check on a working unit and tell you.

[wolfman]

I can't tell, i never measured the voltage at the plots, only the resistance.
I'll check on a working unit and tell you.

That would be nice! Could you post voltage, resistance and a picture of all pots perhaps? I think this might help others too!

An additional asset would be a closeup pic of the laser pot too, just to see in which position it is as a standard...

[deubeul]

No problem. I'll do that this week-end.

[deubeul]

Sorry for the late reply, i had a busy week-end 

So here are the settings of the plots on a flawlessly working unit:



And this is how i measured voltage and resistance:



And now the values:


Voltage:

              AB     AC    BC                 
vr101:  0.36  0.09  0.45
vr102:  1.34  1.25  2.59
vr103:    0     0.02  0.02
vr104:    0     0.03  0.03
vr105:    0     0.17  0.18


Resistance:

              AB      AC     BC                 
vr101: 14.83  4.95   17.78
vr102:  8.21   5.34   10.57
vr103:  3.25  14.75  16.84
vr104:  3.23  15.71  17.70
vr105:     0     0.60    0.60


Just figured i forgot the lens plot pic, i'll post it tonight.

[wolfman]

Thank you for posting your results.

I think I am getting closer. Today I replaced the laser, which gave me bright red spot in the lens. So actually the laser REALLY was dead.

I then adjusted the pots to match your photo (I don´t get the Ohms like you did...they´re never fit near your values, at least on leg on every pot always is off).

Drive would start - sled moves to inner track, laser light is coming on, then silence. No focus movement (I can´t hear ANY). Then the drive shuts off after a few seconds. When I repeat the whole procedure while I hold the drive at an odd angle, the spindle would spin up, run for a few seconds and then the drive shuts off. The "Repeat" light would occasionally light up, and/or the LCD display would flicker.

Is it probably a controller chip on the small board beneath the buttons?

[thesteve]

sounds like your pots may be a bit off

also you wont hear focus, but if you watch the lens it should bob after centering
if instead it jumps to any extreams and stays there you have an open feedback loop in the focus or tracking amp circuit

[wolfman]

also you wont hear focus, but if you watch the lens it should bob after centering
if instead it jumps to any extreams and stays there you have an open feedback loop in the focus or tracking amp circuit

No, it doesnt. Just stays there and doesn´t move at all after centering. Laser light is good though. I wonder what that may be...

[deubeul]

Did you test the lens with your original plot settings? This settings may vary from a system to another...

I think tou're really not far... Try the "by ear" method, i'm sure it will solve the problem now that you have a new lens. It may take time at first, but i you follow carefully the steps of the method, it will eventually work.

[wolfman]

THe only thing that happens is that the LCD flickers, the "Repeat" LED comes on and off blinking very very fast. Drive speeds up only when I hold it at slight an angle...otherwise it doesn´t speed up at all. No pot setting changes that behaviour...

Anyone here that knows a little more on CDROM drives?

[wolfman]

So far I have replaced the CD power driver BAxxxx, and now I get a stable light and there is no erratic lighting up. However laser/sled don´t move anymore - no reaction from the unit except that it is "on". Laser looks perfect bright and sharp.

Unfortunately before I did that an SMD piece burned up and vanished. It is located right beneath the plastic IFU-connector (you cant get to it without completely desoldering it). I am guessing that this is the reason why the CD starts to spin as soon as I switch on the IFU (it didn´t do that before, and the BAxxxx certainly isn´t connected to that, as I replaced it afterwards).

Has someone probably got an idea what that tiny SMD was and knows its values? That would help me.

I am doing my best to get it working...I see it as a test object. Would be happy for any info.

[thesteve]

check the 4 pin ribbon from the laser
sounds like it may not be connecting

[wolfman]

check the 4 pin ribbon from the laser
sounds like it may not be connecting

I don´t think that this will help a lot (laser is completely new), since a tiny SMD below the SCSI connector burned up - the only way to reach it is to completely desolder the whole connector. And then I don´t know what piece it was- resistor or cap, nor the value of it.

Apart from that the CDrom doesn´t boot up in the IFU, but outside of it it powers on...

[wolfman]

check the 4 pin ribbon from the laser
sounds like it may not be connecting

I MADE PROGRESS!!! It wasn´t the 4pin laser ribbon, I checked it with a dead unit - focus worked. And it also worked on the new laser.

Now, a short overview what I did so far:

-changed Laser
-relubed Gears
-changed out broken Gear with Chop´s Gear
-Replaced 7805
-Replaced BA6290A
-complete Cap replacement
-resoldered the burned connection below the SCSI plastic connector (the one that fits into the IFU)
-re-adjusted pots again TODAY to recommended values

Drive now finds TOC!

Only downside:       >>>>>   SLED DOESN´T MOVE AT ALL <<<<<<<
                               >>>>>   LASER ONLY FOCUSES AFTER I TIP IT TO CENTER SWITCH! <<<<<<

Both problems are connected to each other - if sled doesn´t move to center, no focus/CD check.

So do I have a dead sled motor?
Or is it the movement circuit?
Where would I have to look for a dead solder joint considering the sled circuit?

I think I AM VERY CLOSE, since the Drive is finding the TOC, and when I move the pots I can hear that it is going to react to it like everybody else described, so I think the relevant parts must be still functional.

Anybody with a hint perhaps?

[thesteve]

That's what they do with bad gears
Try turning the sled motor by thumb across gear
It should turn easy

Sent from my ADR6300 using Tapatalk 2

[wolfman]

That's what they do with bad gears
Try turning the sled motor by thumb across gear
It should turn easy

Sent from my ADR6300 using Tapatalk 2

It must be the motor. I tested it with a 1.5 V battery, and it ran slowly with intermittent stops (would move on if I turned its gear for a tooth or two). It had trouble running the whole lenght...so I will have to replace it. Let´s see by the end of the week (hopefully I have my replacement motor then), if it was that. I´ve got another drive that is working, and the motor there is much much quieter.

What I saw from chop´s gear is that it puts a lot of resistance on the motor as they turn much harder (even with lubrication and the motor screws  loosened). I think any replacement plastic gear of appropriate pitch size must match.

Did someone perhaps try other nylon gears? Would be interesting to know....