Help with CD drive not spinning

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Ziggy587
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Help with CD drive not spinning

Post by Ziggy587 »

Hey everyone! I'm looking at a Neo•Geo CD for someone, it's not loading discs. It's the original top loader model (not the front loader, and not the CDZ).

These drives seem to break in a variety of ways. The problem that I am having is that the disc isn't spinning. A common reason for that is the lid switch. There's a little shaft on the disc tray lid that'll sometimes break off, so the lid switch is never activated and thus the console thinks it's open. That is not the problem I am having. That shaft has not broken off the lid, and I have even manually actuated the lid switch and confirmed it's functioning as it should.

This drive has two motors, one one for the sled and one for the spindle. The sled appears to operate correctly. If I manually move the lens all the way to the outside, when I power on the console the sled motor kicks on and returns the lens to the inside. With no disc in there (and holding the lid switch down) I can see the lens trying to focus on a disc. So it looks like everything is functioning as it should, it's just that the spindle motor isn't kicking on.

I attached my multi meter to the spindle motor and I never see any voltage there. I measured the sled motor and noticed it was fed about 3v when it was activated. So with the console unplugged, I applied 3v to the spindle motor and was able to get it to spin. So this tells me that the motor itself is OK. The problem must be with the drive's control board. I've traced the motor's connections back to the logic board, and there are no continuity issues.

The motor is driven directly from two pins from a BA6396FP. The datasheet can be found here: https://console5.com/techwiki/images/e/ea/BA6396FP.pdf

Could this part of the IC be burnt out? The sled motor operates correctly, which is also driven from this same IC. The VCC pins measure 7.59v. Looking at the example schematic in the datasheet, it looks like pin 10 controls the output for the spindle motor. There is no voltage on pins 11 and 12 (measured from the motor, there are no components that sit in between).

If it isn't the BA6396FP, any ideas what it could be? I tried searching the internet, and I was able to find two different forum posts that had the same issue as me (disc not spinning, not led switch related) but no answers.




I've also noticed something about the power supply... It's suppose to output 10v and 5v. I measured mine and the 5v line measures 5.6v which seems normal, but the 10v line measures 9.57v which seems odd. Is this normal for this power supply? I've read about issues with this power supply causing disc read problems. I took it apart, the caps aren't bulging and they're all Nichicon brand.

The console otherwise appears to be OK, although without the disc drive working all it can really do is display the splash screen then boot to the CD player dashboard.
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TmEE
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Re: Help with CD drive not spinning

Post by TmEE »

The motor will not spin until CD is detected, there's a good chance the laser is too weak, dead or simply dirty. Motor driver can burn out but you will see signs of it normally (a hole burned in it).
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Ziggy587
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Re: Help with CD drive not spinning

Post by Ziggy587 »

Is that unique to the Neo Geo CD or the BA6396FP ? Because on other consoles I've observed that the disc spins upon power on (or closing the lid switch) but will stop if no disc is detected.
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Re: Help with CD drive not spinning

Post by TmEE »

It is a behaviour I see in almost all CD devices, they only spin up the disc when a reflection is detected. First laser is moved into the center, then beam is turned on and lens goes up and down (focusing) in an attempt to detect the reflection from the photodiode array, once it saw something disc is spun up and data extraction procedures begin. Some drives may spin disc up as the first step but it isn't something I normally see.

I have no personal experience with NeoGeo CD, but I have a lot of experience with other consoles and devices using CDs and in 99% cases it is the laser that is the problem. It is the only real "consumable" in the mechanism. Motors do wear but that takes a lot of time and is uncommon. Only in high speed drives such as one in Dreamcast that use brush motor instead of brushless you see real motor wear caused problems. It is not uncommon there to have burned out motor drivers, but majority of high speed designs use brushless motors so this never becomes an issue.
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Ziggy587
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Re: Help with CD drive not spinning

Post by Ziggy587 »

FWIW on the Dreamcast the spindle motor will immediately start spinning while the lens moves up and down, then stop spinning if no disc is detected.

This all makes sense though. The stock laser seems to be dead, I see no light emitting from it at all. This Neo Geo CD came with a replacement laser assembly, which looks identical to the original but I suspect it also doesn't work (as is common with these cheap Chinese replacement lasers). I'll see if I can find a replacement laser that actually works, and I'll report back if that fixed the issue.

Thanks for the help!
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Re: Help with CD drive not spinning

Post by Pokun »

In very early CD drives, mechanical parts like cogs may wear out. The original PC-Engine CD-ROM2 unit (which is also used with the final PC-88 model) has poor plastic cogs that tends to turn to dust. They also have problems with bad electrolytic capacitors (to the point that about all of them have failed now).
The last PC-Engine models, Duo-R and Duo-RX, have very good quality CD drives built-in however, and they were released 1993 and 1994 respectively, only a year before Neo Geo CD so I guess drives were more stable at that time.
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Re: Help with CD drive not spinning

Post by TmEE »

On that replacement laser there will be a shorted pad somewhere on PCB or flex that connects to the laser. That pad is laser diode power supply and it is shorted to prevent ESD damage to the diode during handling (these lasers are very fragile) and will have to be unshorted for the new assembly to function. All replacements should be shipped in such a state.
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Re: Help with CD drive not spinning

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Ziggy587 wrote: Wed Jun 02, 2021 6:14 am The stock laser seems to be dead, I see no light emitting from it at all. This Neo Geo CD came with a replacement laser assembly, which looks identical to the original but I suspect it also doesn't work (as is common with these cheap Chinese replacement lasers). I'll see if I can find a replacement laser that actually works, and I'll report back if that fixed the issue.
Are CD-ROM lasers even visible? From what I've read in a few places, they run at ~780nm (i.e. infrared) and are "virtually invisible".
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TmEE
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Re: Help with CD drive not spinning

Post by TmEE »

I have not seen a drive with actually invisible laser beam on anything modern (1990+), all show a dull red spot visible through a CD's top surface. Perhaps some early drives have deep infrared (or a much narrower spectrum) laser which beam will actually be invisible.
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Re: Help with CD drive not spinning

Post by lidnariq »

TmEE wrote: Wed Jun 02, 2021 2:50 pm all show a dull red spot visible through a CD's top surface.
I hadn't known this, but the 780nm light used by CDs is just on the upper bound of what's considered visible; in the graphs here 760nm is 4.2 OD (i.e. 10-4.2) less bright than the max at 555nm. So 780nm could well be directly visible, maybe only another order of magnitude dimmer.

I also didn't know this, but apparently really early CD drives used HeNe lasers.
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Re: Help with CD drive not spinning

Post by nocash »

I don't have a PSX here right now, but as far as I remeber, the spindle motor was doing about one full rotation, and then stopped if no disc inserted (the spindle rotation may help to ensure light reflection if the disc was parked in a position that doesn't reflect, or has some scratch or dirt on that position).

I have heard about the PS2 console laser being visible on the top side of the disc (shining through the disc), but I have never seen that in PSX consoles. Even without disc inserted, the PSX laser is very hard to see, I have long considered it as invisinle infrared light because it's only a tiny red light that could be mistaken for a reflection from some other light source, it might be best visible in a completely dark room (and only during the detection when lens goes up/down), and remember that it is a laser, if you are seeing it, then you are probably just slicing your eyes, be careful.
Ziggy587 wrote: Sun May 30, 2021 5:42 pm Looking at the example schematic in the datasheet, it looks like pin 10 controls the output for the spindle motor. There is no voltage on pins 11 and 12 (measured from the motor, there are no components that sit in between).
Looks so going by the example schematic in the datasheet (going by the rest of the datasheet, CH1-CH4 seem to be almost identical (with extra MUTE input for CH1), and one could theoretically use any one of them for the motor). Anyways, if it's wired to pin 11 and 12 outputs, did you check if you can see a voltage on pin 10 input? It might be only a relative short pulse to give a small push to the motor.
Pin 9 input gain adjust is left unconnected in your drive? It looks as if it could be wired to an optional potentiometer or so.

If you are running out of ideas, and have no other replacement parts at hand, and if the PCB wires are accessible... you could try to cut and swap wires to the spindle and sled pins on the BA6396FP chip, if CH2 is broken, then spindle should start working, and sled should stop doing so.

My other idea was about dirt in the door close switch switch, or in the sled pos0 switch, but I guess the lens up/down stuff wouldn't even start if one of that switches were dead (and the sled mechanics would make a terrible scratch noise if the pos0 switch wouldn't stop them).
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Ziggy587
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Re: Help with CD drive not spinning

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TmEE wrote: Wed Jun 02, 2021 2:36 pm On that replacement laser there will be a shorted pad somewhere on PCB or flex that connects to the laser. That pad is laser diode power supply and it is shorted to prevent ESD damage to the diode during handling (these lasers are very fragile) and will have to be unshorted for the new assembly to function. All replacements should be shipped in such a state.
I read in a random forum post (I can't find the link now) that this specific laser assembly doesn't have any shorts that you have to open. Could that be possible?

edit: Here it is: https://www.reddit.com/r/neogeo/comment ... ic_solder/
Quietust wrote: Wed Jun 02, 2021 2:44 pm Are CD-ROM lasers even visible?
nocash wrote: Wed Jun 02, 2021 6:24 pm and remember that it is a laser, if you are seeing it, then you are probably just slicing your eyes, be careful.
You can definitely see it, unless I was hallucinating. Maybe it differs between drives. But yeah, I never look straight into the lens.
nocash wrote: Wed Jun 02, 2021 6:24 pm Looks so going by the example schematic in the datasheet (going by the rest of the datasheet, CH1-CH4 seem to be almost identical (with extra MUTE input for CH1), and one could theoretically use any one of them for the motor). Anyways, if it's wired to pin 11 and 12 outputs, did you check if you can see a voltage on pin 10 input? It might be only a relative short pulse to give a small push to the motor.
Pin 9 input gain adjust is left unconnected in your drive? It looks as if it could be wired to an optional potentiometer or so.

If you are running out of ideas, and have no other replacement parts at hand, and if the PCB wires are accessible... you could try to cut and swap wires to the spindle and sled pins on the BA6396FP chip, if CH2 is broken, then spindle should start working, and sled should stop doing so.
I did not detect voltage on pin 10, but I don't have a scope so I'm only checking with a DMM. If it is just a quick pulse, I probably can't catch it.

Good idea, I had thought about trying another channel form the BA6396FP. But if the assumption is correct that the spindle motor wont engage unless a disc is detected, then another channel would also appear dead. Right?

I didn't really trace much out, this board is kind of a pain in the ass. There are 5 trim pots though.

https://console5.com/wiki/Neo_Geo_CD_To ... djustments

I'm going to try another replacement laser assembly. It's just that, from what I gather, they're pretty hit or miss if they will actually work. This Neo Geo CD came with the stock laser and a replacement laser. On the replacement laser, the intensity trim pot just spins around and around, which usually happens when you overheat them. So I'm wondering if that happened during the manufacturing process, that would paint a picture of how low quality these things are.

The laser assembly appears to have been made by Sharp, and I wonder if it's exclusive to the Neo Geo CD. Probably not, right? So while the only replacements are cheap Chinese ones that are probably clones, it would be interesting to find it in another piece of equipment from the early 90s. Perhaps a Sharp CD player. I'm really not a fan of cannibalizing parts, but it would be a good way to get a legitimate replacement part instead of a poorly made clone.


This video is interesting. I haven't had a chance to watch the entire thing, but it looks like he's had all sorts of temperamental problems with the logic board: https://www.youtube.com/watch?v=5VDk2AH4rdc
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Re: Help with CD drive not spinning

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Ziggy587 wrote: Wed Jun 02, 2021 8:32 pm This video is interesting. I haven't had a chance to watch the entire thing, but it looks like he's had all sorts of temperamental problems with the logic board: https://www.youtube.com/watch?v=5VDk2AH4rdc
So I watched this video to the end. I didn't watch every last minute of it, I skipped forward to get the meat and potatoes. The entire video, he's struggling to get the Neo Geo CD to read discs. It's working, it's not working. He suspects various things. Trim pot settings, laser intensity, various ICs, works when warmed up but not cold. But in the end, he puts a new laser assembly in it and then it works perfectly. Occam's razor, I guess.
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Ziggy587
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Re: Help with CD drive not spinning

Post by Ziggy587 »

So I got a new laser assembly in and installed it. Unfortunately, I'm getting the same results. If I move the lens all the way to the outside, it'll return to center upon powering on the console but that's the only sign of life that it shows. The disc never spins up. If I put a disc in while the system is powered on, I hear no activity and then I get an "insert CD" message on the screen. I tried adjusting the pot on the laser assembly, all the way clockwise, all the way counter-clockwise and in the center. Still nothing.
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Re: Help with CD drive not spinning

Post by Memblers »

Sorry to hear that. You probably know of it already but I'd mention just in case, that if you're unable to restore it, another option is to replace with this optical drive emulator: http://furrtek.free.fr/sdloader/

I wouldn't trust 30 year old electrolytic capacitors to still be good, but OTOH it doesn't seem like there would be much power involved with detecting a disc, so that doesn't seem likely to fix it, either.
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