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MCD CDX - New Laser Installation Disc Won't Spin

lcizzle

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Original poster
Feb 22, 2022
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Hello,

I purchased a working CDX many years ago. Broke it out of storage recently to play some old games. The CDX was starting to exhibit loading issues. Disc would spin, stop, spin, stop, Some games have better success than others. Some would play but have extended load times and others wouldn't make it past the title screen. Before seeking out a laser replacement I did some minor maintenance and cleaned the machine out and applied some white lithium grease to the rails thinking the dryness may cause it issues with loading. Loading didn't improve so I purchased a laser replacement (3 to be exact).

The lasers are labeled as follows.
SF-C93
SF-C93AQ

None of them seem to work fully. I can get all of them installed and when inserting a disc the laser head will move but the disc won't spin. (solder blob removed) When I reinstall the factor laser the discs will spin but have the issue above.

Any ideas? I'm not an eletrical engineer (yet) and have proper tools. Just need pointing in the right direction by someone more experienced.

Thanks for any help!

Edit:

Sega CDX MK-4121
 

Trimesh

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There are two different versions of the C93 optical pickup with different photodiode layouts - if you look at the place where the diode array solders to the flex PCB there should be 5 pins showing past the edge of the screening - if there are only 4 then you have the wrong version.

I'm not quite sure why Sanyo decided to make two different very similar looking but incompatible OPUs with the same part number, but they did...
 

lcizzle

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Feb 22, 2022
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Are you referring to this? If so all 4 lasers are identical.

Free-Shipping-SF-C93-4-Lines-Laser-Lens-SFC93-10-Pin-Optical-Pickup-For-VDO-Becker.jpg_Q90.jpg_.webp
 

Trimesh

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Yeah - but that's the 5 pin version, which is correct
 

lcizzle

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Feb 22, 2022
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I checked again after you confirmed and used magnification as well. All 4 lasers match the image above (5 pin). 3 track but don't spin, 1 (factory laser) works but is just about dead.

Edit: I'm not adverse to buying another laser if someone has a reputable vendor they can provide. Ebay looks to be hit or miss, mostly miss.
 

bart_simpson

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Aug 10, 2019
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Be careful I got a few places I got the lasers from have been dud lasers so becareful.
I hope to try again and find a good seller of them.
 

Tokimemofan

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May 30, 2019
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You should check the spindle and tracking motors, they often become electronically noisy with age. This will almost always look like a faulty laser unless you know what to look for
Edit: a simple way to do this is to measure the motor with an ohm meter and turn it in small increments, the non moving resistance should be consistent a bit above 10 ohms on the spindle motor, if you see it jumping around to random numbers after turning it it’s probably bad. Both motors often exhibit the same behavior because of internal oxidation
 

lcizzle

New member
Original poster
Feb 22, 2022
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You should check the spindle and tracking motors, they often become electronically noisy with age. This will almost always look like a faulty laser unless you know what to look for
Edit: a simple way to do this is to measure the motor with an ohm meter and turn it in small increments, the non moving resistance should be consistent a bit above 10 ohms on the spindle motor, if you see it jumping around to random numbers after turning it it’s probably bad. Both motors often exhibit the same behavior because of internal oxidation
Motor definitely works. If I put in the factory laser it tracks and the motor spins, games load but really slowly but they also hang or don't play music because the laser is dying.

Edit: I've tried 3 different lasers now and nothing. sucks. I have a model 2 system that's doing the same exact thing. Factory laser tracks, plays games but due to the laser dying music doesn't play or the games hang. Put in another laser and it doesn't track and discs don't spin. I'll figure it out or find the proper laser one of these days.
 

Tokimemofan

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May 30, 2019
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Motor definitely works. If I put in the factory laser it tracks and the motor spins, games load but really slowly but they also hang or don't play music because the laser is dying.

Edit: I've tried 3 different lasers now and nothing. sucks. I have a model 2 system that's doing the same exact thing. Factory laser tracks, plays games but due to the laser dying music doesn't play or the games hang. Put in another laser and it doesn't track and discs don't spin. I'll figure it out or find the proper laser one of these days.
Did you test the motor to confirm it works perfectly or did you just assume that because it spins a disc and the laser moves that the motors are good. It isn’t that simple, a failing motor usually causes read error on an inconsistent basis ranging from usually booting and skipping audio to usually not even fully spinning up the disc. The problem is so common that I check the motors with an ohm meter before doing anything else. Often I find huge resistance spikes depending or the rotational position.
That unit read games about 80% of the time but would hang on loading screens on most games
Both the spindle and tracking motors are prone to this. No guarantees this is your problem but it needs to be checked
 

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