Servicing NeXT (Canon) MO Drives

Started by korneluk, June 28, 2007, 06:27:00 pm

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korneluk

This is a community work log to develop a DIY troubleshooting and service manual for the Canon magneto optical drives in the original NeXT black cubes.

It's a collective effort by the NeXT community to gather as much information as possible and document via pictures the workings of these units. Feel free to join in on the discussion and help us revive those remaining MO drives.

Thanks all,

-- josé k.

pentium

I have ben longing for a thread like this.
If I can get my hands on a known dead drive I could completely dismantle and photograph it for everyone.

-NeXT 68040 Cube with NS 3.3 and 64Mb ram

da9000

I can't believe you didn't snag this one pentium:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300126036399

You've been drooling for a MO drive for ages! Where were you during the auction!??!!?! It was a steal!

pentium

QuoteWhere were you during the auction!??!!?!

Entering the second week of a six week cadet training course.
I didn't have internet access the whole time. I agree, it was a good deal. damn....

-NeXT 68040 Cube with NS 3.3 and 64Mb ram

gtnicol

I put some photos of a disassembled NeXT MO on flickr.

http://www.flickr.com/photos/15578792@N02/1832503846/in/photostream/

The drives appear to be robustly built. I'm surprised they're so flaky. My guess is that the optical linear encoder is subject to getting dirty and/or stretching.

pentium

Well I see at least one chip that says Canon on it so that looks good.
First thing that comes to mind is the fact that most MO drives when they go just seem to spin up and down over and over again.
A while back the cd drive in my powermac was acting exactly like a NeXT MO drive that was bad:
-You inserted a cd and it would spin up and down several times then do nothing.
-The drive would work fine at first but later start to spin up and down.
-While the drive was spinning up and down the system would feeze and wait for the drive to work properly.
-Since NeXT MO drives came only in one speed (well, two if writing uses a different speed) the media MUST be spinning at the proper speed or you won't get a proper read.
Think back to the days before 2X cd drives and you might remember this.
I have a feeling that either the main motor that spins the OD was of bad design or fo some reason the drive can't properly determine what it's current speed is (like driving without a dashboard).
In the event of a possible bad motor, we can test that theory by swapping the motor in question with one from a known working drive.
When it comes to controlling the speed I don't know how NeXT or Canon designed that. It might be an IC or some sort of sensor (like a tachometer).

-NeXT 68040 Cube with NS 3.3 and 64Mb ram

gtnicol

Quote from: "pentium"
I have a feeling that either the main motor that spins the OD was of bad design or fo some reason the drive can't properly determine what it's current speed is (like driving without a dashboard).
In the event of a possible bad motor, we can test that theory by swapping the motor in question with one from a known working drive.
When it comes to controlling the speed I don't know how NeXT or Canon designed that. It might be an IC or some sort of sensor (like a tachometer).


I've found 3 main classes of problems in the drives (after many hours of swapping/cleaning parts).

The first does appear to be a problem with the motor or the driving circuit. On some drives, running a heat gun over the board helped the motor to spin properly. On others, the motor just seems flaky.

The second is a problem wit the optical linear encoder. They get dirty or otherwise don't seem to work. Also, I found that placing the head back into the 'home' position helped the drives work in some cases.

The third is poor connections, not just on soldered joints, but also on the ribbon cables. In some cases, just reseating the ribbon cable allowed a drive to spin up, that otherwise would remain silent.

The boards at the top of the drive seem, for the most part, to be reliable (i.e. swapping boards didn't make much difference).

When I have a bit more time to be a bit more methodical. I wish I could find either a NeXT or a Canon field service manual as I'm sure some of the problems are calibration issues, and there are little trim pots in many places.

pentium

Well because the motor circutit on my drive decided to act p today I thought it might be a little nice to describe how to separate the top and bottom of the drive.

First off, take these four screws out.


Next, put the drive up on it's end and gently pull at the top. The top cover on the drive will swing down.


Next, disconnect these two ribbon cables.


Now swing the top closed again and flip the drive over and remove four more screws.


Now put the drive back up on its end and gently pull at the top of the other side of the drive. After you disconnect these two wires, putt the bottom outwards to separate the laser assembly from the system.


To remove the other side, unplug the other ribbon cable and the wires marked by the arrows.


Remove the two screws that were giving you that hinge-like action earlier. The cover as well as the logic boards can now be removed.


One other thing. Your drive may not have it but when you separate the two main logic boards, be careful of the green wire that's connected between the two boards.


EDIT: One last thing regarding the motor assembly. On my drive I noticed that the largest chip on the motor board (looks like a switcher for the motor itself) has several pins that look like they have either had something get on them and  cause the pins to oxidize or they have been exposed to large amounts of heat. The chip itself could be the reason the motor is either not starting, not stopping or not properly getting up to speed.

-NeXT 68040 Cube with NS 3.3 and 64Mb ram

idylukewild

Thanks, pentium, for going to the trouble to photograph and post photos of the OD. Between what you and gtnicol are doing we may someday find a way to fix these pesky drives. I'm wondering if something gets 'banged' out of spec (calibration) from repeated use. Perhaps there are trim pots to get things back within spec. It's very odd that some OD have refused to work new out of the box, though. My OD which worked for a few hours on about 10 disks then went into a perpetual 'spin up - spin down -spin up' mode (a mode it goes into each time I've tried to use it since) is also puzzling. When I get time I hope to look for any adjustments - specifically trim pots - and wiggle them around a little to see if it gets the OD working again. Incidentally, my OD looked brand new and dust free when it failed and had worked a fine the few times I used it briefly before my two-hour marathon session.

Luke

gtnicol

There are lot's of little trim pots on the drives and I'm sure that part of the problem with these things is calibration... I can hear the difference in motor speed between drives that work and drives that don't.

FWIW. I have found that reflowing some of the joints is a worthwhile effort... it can often get a dead drive to at least spin again.

pentium

I'm taking interest in the damage I saw on the motor controller board. Sorry I don't have a pic of it but I don't want to dismantle my cube and MO drive again for a single photo.
Anyways, It might be nice is someone else who was having motor troubles could take their drive apart and we could compare what the motor controller looks like.

-NeXT 68040 Cube with NS 3.3 and 64Mb ram

gtnicol

FWIW. I have found (by swapping boards/motors etc) that the motor driver is the primary suspect. That and the linear optical encoder.

Next up is the servo controller board on the back of the drive.

The top logic board doesn't seem to fail often (maybe one out of 15).

pentium

Well in that case I have a feeling that the motor driver is simply overheating and burning out either completely or partially. It does seem to get pretty warm during operation. do you think a little heatsink would fix this?

-NeXT 68040 Cube with NS 3.3 and 64Mb ram

gtnicol

I don't think the heatsink would help... the later model canon drives don't have one. It might be worthwhile swapping out, but I'd go through looking for dry joints first.

pentium

Quote from: "gtnicol"I don't think the heatsink would help... the later model canon drives don't have one. It might be worthwhile swapping out, but I'd go through looking for dry joints first.

*sigh*
Well there is a reason to open the thing up again as I saw quite a few of those.
I'll take some photos tonight.

EDIT: okay, here is how you remove the motor assembly.

Requirements: the optical assembly (the bottom of the drive) has been removed.

All you have to do is remove the three screws (1, 2 and 3) and then carefully pull the motor out parallel to the entire optical assembly (4)


What I have noticed is that the pins I marked with arrows seem more oxidized/discolored than the others. I have yet to go at the joints with my iron in this photo and I'll go at them after dinner.


EDIT: In my case at least, reheating the joints did not stop the motor from constantly spinning.  :(

-NeXT 68040 Cube with NS 3.3 and 64Mb ram