PROGRESS on CD-ROM² Repair

[wolfman]

Recently I acquired a Cdrom that was marked as "non-working". After I relubed the rails it played the first 2 tracks fine. Then it went out and didn´t start again (original middle gear broke into two). I got chops replacement gear from Fidde_se and then it played again, though only roughly 3/4 of an Audio CD.

So I decided to replace all the caps after reading about the whole procedure and tried myself with adjusting it. I am 80% trough this whole thing, only caps I left over are where all the cables are below the switches (they´re tiny and there´s hardly space for my fingers, so I left them where they are). Now all I get is a sound from the sled, which is checking its starting position, and then theres silence. No matter which pots I adjust or which position they have, just nothing.

I must say that I did very thorough reading on the whole re-aligning and re-capping procedure.

What did I do wrong? Any opinions? I appreciate any help!

[Keith Courage]

Hmm, I haven't had that problem before but maybe check that you didn't accidentally install two polarized 10UF caps where non-polarized ones should be used. Also, take a good look at the solder points for the capacitors on the board. I've seen a few pads that can lift up requiring a new lead to be soldered to it.

[wolfman]

Hmm, I haven't had that problem before but maybe check that you didn't accidentally install two polarized 10UF caps where non-polarized ones should be used. Also, take a good look at the solder points for the capacitors on the board. I've seen a few pads that can lift up requiring a new lead to be soldered to it.

No, I definitely didn´t take the bipolar ones out, cause I didn´t have replacement for them.
I can send you a photo of my soldering...looks very clean. But maybe you´ll see something, that I havent seen. I am professionally blinkered by now....

[wolfman]

Also, take a good look at the solder points for the capacitors on the board. I've seen a few pads that can lift up requiring a new lead to be soldered to it.

Hey, I have uploaded 2 pics of the underside of the board. Do you want to take a look at it? Maybe you see something I don´t.

http://www.flickr.com/photos/65709578@N06/sets/72157640174676445/

[Fidde_se]

If tricking the sled door, does the laser light up? any cracks in the pots plastic case?

I'v heard that when trimming the pots to far (certain pots) out of their position can burn the laser for good, that definitely goes for the pot on the laser, which should not be tweaked unless the laser is on it's last toes and need just some extra juice to crack it up.

And sometimes when adjusting the pots just the slightest, either by ear or by measuring it can make it go from read bad to not at all, when it stops spinning you know it's to far.

[wolfman]

If tricking the sled door, does the laser light up? any cracks in the pots plastic case?

I'v heard that when trimming the pots to far (certain pots) out of their position can burn the laser for good, that definitely goes for the pot on the laser, which should not be tweaked unless the laser is on it's last toes and need just some extra juice to crack it up.

And sometimes when adjusting the pots just the slightest, either by ear or by measuring it can make it go from read bad to not at all, when it stops spinning you know it's to far.

So which pot exactly is the one for the laser? Descriptions on the forum here don´t name it directly.... Is it the far left one when you look from the side, in normal position (cdrom on the table with board on the underside)?

[BlueBMW]

There is a pot on the laser unit itself, not the mainboard.  You should never have to adjust that one except in the most extreme of circumstances.

If you need a new laser, let me know.

[wolfman]

There is a pot on the laser unit itself, not the mainboard.  You should never have to adjust that one except in the most extreme of circumstances.

If you need a new laser, let me know.

Oh, I am sure I never touched THAT pot! Still I don´t see light coming thru the lens, so there must an issue. Don´t know where though.

One thing though I noticed today:
When I put everything togehter into the IFU, and I switched on the LT (with a game hucard in it) and right after the CDROM, it would spin up, and after the game had loaded, would stop. This is somehting it doesn´t do when I have a music cd in it - it simple would move the sled to check the for correct position, and then the unit goes off. Any hint?

Btw, thank you for your laser offer, I´ll get back to you, if I don´t get it sorted the normal way.

[BlueBMW]

Power the unit on open the lid and hold the little lid closed switch with a small screwdriver or whatever and press play and see if the laser tracks to center, turns on and then bobs up and down a few times.  That would tell is where in the process it is breaking down.

When it power up the first thing the system does is move the laser to center.  Once the center switch is tripped, the laser powers on and moves to check for the presence of a disc.  If a disc is seen, the drive spins up and the laser moves to read the TOC.  If no disc is seen, the laser stops and shuts off.

[wolfman]

Power the unit on open the lid and hold the little lid closed switch with a small screwdriver or whatever and press play and see if the laser tracks to center, turns on and then bobs up and down a few times.  That would tell is where in the process it is breaking down.

When it power up the first thing the system does is move the laser to center.  Once the center switch is tripped, the laser powers on and moves to check for the presence of a disc.  If a disc is seen, the drive spins up and the laser moves to read the TOC.  If no disc is seen, the laser stops and shuts off.

Sled checks for position, actually I CAN hardly see the laser turn on, and then there is nothing. After a few seconds the unit powers off. And then I cant get it to power on again (it only powers on again in the IFU  ), I have to remove the power plug.

So far it goes, but then nothing more.... 

[BlueBMW]

If you're getting a very weak laser then I'd suspect something with the laser or its connections, not the pot adjustments.

[wolfman]

If you're getting a very weak laser then I'd suspect something with the laser or its connections, not the pot adjustments.

Do you have a closeup photo of that laser pot? I actually don´t see any pot on mine - whether on the cable nor on the laser unit itself....

[wolfman]

What puzzles me is the startup-sequence:

I switch on the CDrom, the sled moves 1mm back and forth (innermost position), silence, moves 1mm back and forth, silence. Shutoff. I cannot switch it on again, I have to remove the plug, wait a few secs, and only then I can switch it on again. It also doesn´t matter which Audio-CD I use, always the same behaviour.

What is causing this?

[BlueBMW]

Can you take a picture of the postions of the five pots on the mainboard?

[wolfman]

Sure, here it is:

http://www.flickr.com/photos/65709578@N06/12192888985/#


Like I said, I am sure that I touched them without noticing during the cap replacements....

[Keith Courage]

That is very odd to see those pots in such a position but I have seen some vary here and there.

Try setting the pots similar to this picture and see if it changes anything:

[deubeul]

The ribbon cable doesn't seem to be correctly plugged...

[Keith Courage]

It is plugged in correctly in the picture I just posted for you to see. Check and make sure yours is the same.

[wolfman]

Hi, thanks for the help.

If look closer you´ll see that it is correctly plugged in (compare it with the solder spot,, your picture and mine). I already tried the pots like in the picture you mentioned, unfortunately to no avail.

I measured voltage across all pots and the only one that gives a good return is Pot #2 (right of ribbon cable connector), 2.25-2.35 V. The other pots are dead at all or give odd results like 1.7 V, 0.5 V or 0.7 V. I used a hq volt meter, so this is certainly not an error deviation. Re-adjusting with measurements didn´t change that much. I am beginning to believe it is the CXAsomething IC, that is connected to pot #1....but I am not sure as I don´t not what values it should deliver...

[wolfman]

If tricking the sled door, does the laser light up? any cracks in the pots plastic case?

I'v heard that when trimming the pots to far (certain pots) out of their position can burn the laser for good, that definitely goes for the pot on the laser, which should not be tweaked unless the laser is on it's last toes and need just some extra juice to crack it up.

I could try replacing them. Would make sense. I don´t know them by value, what would be an appropriate replacement?

[deubeul]

I say that because it seems a little crooked...( hope it's the right word )
Did you already plugged/unplugged the ribbon cable? I had one with a blended and uncoupled pin that you couldn't see from the outside.

It could also be the laser limit switch... did you read that topic? https://www.pcengine-fx.com/forums/index.php?topic=7012.0

[wolfman]

It could also be the laser limit switch... did you read that topic? https://www.pcengine-fx.com/forums/index.php?topic=7012.0

Cable contacts are good, I measured them - power gets through to the laser pcb.

Limit switch does give contact, when you push the pin in - I measured with my voltmeter. That shouldn´t be the problem - it would try to move beyond the spindle if there were no contact.

[deubeul]

I had the same problem, the switch worked, but the lens wasn't going far enough to fully push on the switch, i just 'forced' the lens one time to make a deep contact to the switch and now the unit works.

If the problem is the plot adjustment, knowing that the values measured at the plots can vary from a console to another, I recommand you to use the "by ear method" described here: once you're used to it, it's very easy to adjust the lens in any Nec Cd system.

[wolfman]

I had the same problem, the switch worked, but the lens wasn't going far enough to fully push on the switch, i just 'forced' the lens one time to make a deep contact to the switch and now the unit works.

Thanks for the hint - I´ll try that!

[deubeul]

yup sorry i forgot tu put the link for the 'by ear' method:
 https://www.pcengine-fx.com/forums/index.php?topic=8926.0

[wolfman]

yup sorry i forgot tu put the link for the 'by ear' method:
 https://www.pcengine-fx.com/forums/index.php?topic=8926.0

thanks, but adjusting "by ear" would require the cd actually spinning - which isn´t the case with my drive. i see the laser light, the sled doesn´t move and no spin at all (motor isn´t dead though). I moved the sled halfway into the middle of the worm gear and after a start up it doesn´t move back to the center - the laser keeps lighting, no reaction.

This happens now since I replaced the caps near the volume wheel, that I originally left untouched, as I didn´t have a replacement for them till yesterday.

[deubeul]

First step of the method is to make the cd spin    loook for the VR102 passage...

"
Addendum:  Adjusting the pots by ear!

Adjusting your duo's pot can be a daunting task for anyone.  With the high cost of replacement hardware, none of use want to permanently damage our precious Duos!  Here I will try and explain in idiots terms, the adjustment of the Duo pots.

Preliminary setup:

I do my adjustments live.  Meaning I have the system on and hopefully spinning / reading the disc while I do adjustments.  To facilitate this, I remove the magnet from the CD lid (turn the retainer ring until it releases the magnet)  And then I place a piece of tape or whatever over the lid closed switch.  At this point I place an audio CD on the spindle and place the magnet on top of it to hold it in place.

Adjustment:

I use a small philips screwdriver to turn the pots.  If you look closely at them, they have 4 little notches that a screwdriver fits into perfectly.

Once you have a CD in place and everything is ready to go, turn on the system.  If you don't want to connect your Duo to a tv, you can use headphones instead.  Press the run button on the controller.  If the CD starts spinning.... Great!  If not, we'll start with two of the pots:

VR102 and VR104

VR102 has a small range of adjustment in which the CD will start to spin.  If you turn it and the cd starts to spin, then you know you have found one end of the adjustment.  Keep turning it until the CD stops again.  Once you know approximately where those two points are, you can find a sweet spot in the middle.

VR104 seems to be similar to VR102 in that there is a certain range in which the CD will spin.  Again try and find the sweet spot in the middle of the two points of spin/no spin.

By this point, hopefully you have the CD spinning, and maybe even attempting to read!  So lets move on to the next pot/s.....

VR101 and VR103

VR101 is kind of a by ear pot.  There seems to be a small range that works for proper cd playback.  Typically it seems to be in the 0 to 45 degree range with 0 degrees being horizontal.  You should hear some scratchy funny noises when VR101 isn't adjusted properly.  Try and find a quiet spot for it.  If you go too far it will get very noisy.  Hopefully you can find a spot where the CD audio will start to play.

VR103 is, from what I can tell, an error correction adjustment.  Hopefully you have got a CD spinning reliably at this point.  You might hear a whiney faint scratchy noise at this point.... adjust VR103 clockwise until the noise goes away.  If you go too far, the noise will come back only it will be a lower tone and not sound good.   Try and find the sweet spot where the laser operates quietly.

VR105

Lastly, VR105....  This is an adjustment for the spindle speed correction.  I'm not 100% on the best way to describe adjusting this one.  Basically if the spindle speed starts to run away (go REALLY fast) then you've gone too far.  Hopefully by this point, your CD will play music.  Try and play later tracks on the CD and if they struggle to play, try adjusting VR105 until you can play all the tracks reliably.

[wolfman]

Thanks for trying to help me, I already got the right values for VR102, but I never get the spindle to spin. I JUST DON`T GET THE RIGHT VOLTAGE on the other pots, so adjusting is useless...

I already replaced the 7805 voltage regulator just in case.

What else could be the problem?

[deubeul]

Maybe the lens itself.

When the cd still doesn't work after having set the plots, i assume the lens is dead and just swap it with a new one. Always worked 'til now.

[wolfman]

Maybe the lens itself.

When the cd still doesn't work after having set the plots, i assume the lens is dead and just swap it with a new one. Always worked 'til now.

Well, strange situation. I can adjust VR102 freely in Voltage, but when I turn the other pots, the values don´t change AT ALL. Is it really the laser? I can see it light (weak though, hardly visible).

[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:

hostingpics . net/viewer.php?id=194040IMG00005.jpg
hostingpics . net/thumbs/mini_194040IMG00005.jpg

And this is how i measured voltage and resistance:

hostingpics . net/viewer.php?id=325616IMG000099.jpg
hostingpics . net/thumbs/mini_325616IMG000099.jpg

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 2

[wolfman]

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

[Keith Courage]

Check to see if the middle gear moves freely with your fingers.

Usually the middle gear swells up over time making it almost impossible for the motor to spin it.

[wolfman]

Check to see if the middle gear moves freely with your fingers.

Usually the middle gear swells up over time making it almost impossible for the motor to spin it.

It´s a chops gear, so it cant swell 

[Keith Courage]

Oh okay, I must have skipped over the part where you mentioned changing the gears.

[thesteve]

Even chops gears should turn easily
If not run a paper between the gears with the motor screws slightly loose to set the tooth fit  2

[wolfman]

So I replaced the motor today, which is totally new (Mabuchi FF 050SH). Gears turn easier now than before.

But the motor still won´t spin up for some reason, the sled stays where it is, no matter where. Only after I push it to the center switch the laser comes on, starts focusing, finds disc, spindle starts, TOC read. But NO SLED MOVEMENT.

The strange thing is, before I replaced the dead laser the sled moved!

Whats causing this?