Iomega ZIP 250 USB teardown and hopefully repair. (SORTED)

[CatalinaWOW]

I came across some old zip disks that I wanted to read and went through the files until I found my Iomega ZIP 250.  No bueno, couldn't read disks, and in fact, couldn't eject one once inserted.  After a quick look at Ebay and others and finding that they are selling for new or higher prices I decided a repair attempt was in order.

The first stage of this, the tear down, should be beneficial to anyone working on these.  YMMV on the rest.   So first, don't do what I did, prying the lock tabs off the sides to get the top off.  That works, but I couldn't do it pretty, and I doubt anyone can.

The proper first step for disassembly is removal of the front bezel.  The two snap hooks on top, marked by blue arrows are easy.  The other three have a lock in place mechanism and are much harder.



Next peel the two rubber handgrips off of the sides.  After cleaning some adhesive this will expose one screw on each side.  After removing these screws the inner workings slide out the front of the case.  You can see from the picture that my drive will never be pretty again.  Oh well, yours can be.

[CatalinaWOW]

Mine turned out to have at least two problems.  The simpler one is that the clear plastic piece connecting to the front panel button had come out of position and was only intermittently contacting the switch it was meant to drive.  Loosening the PWB and repositioning sorted this problem.

The second problem is more serious.  The heads are driven in and out by the simple voice coil type assembly in the middle of the unit.  The white nylon box in the right rear contains a series of gears and levers used in ejecting the drive, and most importantly drives a mechanical arm that retracts the heads and holds them motionless any time a disk is not being accessed.  This mechanism was not working.  By using a finger to move the restraint mechanism I was able to read disks, but this is definitely not a practical solution.



The spur gear has come loose from the shaft and is not driving the chain.  The picture was taken after moving the gear back to its approximate correct location.  It had slid to the right on the shaft.

My first attempt at repair moved the spur to far to the left and resulted in ineffective engagement.  The adhesive is setting on the second attempt and I will report the results.

Getting the right amount of CA to stick the gear to the shaft without gumming up the works is tricky.  I trimmed all but two fibers from a small paint brush and was able to get a proper amount.  If doing it again I might leave three or four fibers. 

(Sharp eyes might note the black wire going nowhere on the motor.  It got pulled off the back terminal during all the head scratching and is now solder back in place.)

[CatalinaWOW]

Well I either need to be more patient on the adhesive or try another adhesive.  It worked for about three disk reads before the spur gear starting slipping on the shaft.  I am sure I'll get this figured out.  If nothing else I'll use the green aerospace stronger than granite adhesive.

Hope this find salvages some dead zip drives out there.

[CatalinaWOW]

One more thing that became obvious on teardown, and was probably in the manual but long forgotten by me is that there is an emergency eject mechanism.  A paper clip insert to the left of the action button on the front panel will engage the flat black piece.  Pushing it in (toward the rear of the drive) ejects the disk.

[CatalinaWOW]

Getting the shaft and bore of the spur gear well wetted with CA and then letting it thoroughly cure (overnight) turned out to be all that was required.  Have read, written and formatted several disks with no issues.

[guho]

OP: would you know how to fix a 250MB Iomega Zip drive (SCSI), which accepts 100MB media but rejects any 250MB disks right away? The two disk types have different retroreflective markers. I wonder if there are multiple LEDs  or just one for all types. I see no light coming from the media detection LED when inserting a disk so it could be an infrared LED too.

[CatalinaWOW]

Sorry, I haven't looked into this.  Don't have any of the high capacity disks.  In fact I transcribed all the ZIP 100s and got rid of them too.  I still have the drive, "just in case", but don't currently foresee a need.  Kind of like the 512kb 5 1/4 drives I have.

[CaptDon]

We had dozens of these external ZIP250 drives die. They were the parallel port com versions. Insert disk, click,click,click,click.....Push eject button, repeat!!! Never bothered to fix them, technology quickly marched along to USB storage. I still have an internal IDE ZIP250 drive and have rescued tons of other peoples data for them.

[guho]

I am hoping to get mine working again to use on my retro Amiga computer. It's a SCSI 250MB zip drive; they still fetch a lot on eBay.

Could someone help me identify these components (one with two Y and two black ones without markings; see images)?

[guho]

Besides identifying components, how would I troubleshoot this disk detection circuit? There is a yellow LED. I think it is infrared. But it has a weird black dot on the bottom left. Could that mean the LED is broken or corroded? Or is the dot normal. it is not dirt that can be scraped off. What type number should I look for if I want to order a replacement LED? The bottom contacts of the LED seem separate but there is continuity between them. Then there are the photodetectors. They seem covered with infrared filters. There are two detector modules with two detectors each. One detector module points up from the board whereas the other detector pair is at maybe a 30 degree angle. The relevant Iomega patent talks about special retroreflective materials that reflect very differently than normal surfaces of the same color. So this circuit can not be fooled by a mirror or plain paper of the same color as the spot on genuine disks.

Symptom I have: 100MB ZIP disks are accepted. 250MB discs ejected immediately. Fake insertion (pretending to insert a disk but there is air above the detector) also leads to ejection as expected. I have not connected my oscilloscope to anything yet.

[CatalinaWOW]

It occurs to me that if the detection process depends on the unique reflection properties of a thin film in the disk that the problem may lie in the disks rather than the player.  These things are twenty or so years old now and any number of things could have happened.  Does anyone out there have working ZIP 250s?

[CaptDon]

Of all the ZIP100 and ZIP250 disks handed to me for rescue they have all worked unless physically damaged by what would appear to be a user-induced head crash with visible damage to the disk.

[geggi1]

The component with  the Y looks like it is some kindof inductive device.
It might be the same kind as the isolation transformers used on network cards.

[CatalinaWOW]

Of all the ZIP100 and ZIP250 disks handed to me for rescue they have all worked unless physically damaged by what would appear to be a user-induced head crash with visible damage to the disk.

Doesn't sort this case, but it is a happy answer.  Resolving the problem I postulated would be difficult.

[guho]

It occurs to me that if the detection process depends on the unique reflection properties of a thin film in the disk that the problem may lie in the disks rather than the player.  These things are twenty or so years old now and any number of things could have happened.  Does anyone out there have working ZIP 250s?

Yes the thin film on 250MB disks is matte yellowish-green. Very different from the 100MB disks that have a clear plastic pattern. I've tried several disks, which are accepted by my USB and ATAPI 250MB drives, in this scsi 250MB drive and they are all rejected.  I think I will replace the LED and see what happens. Is it obvious to anyone whether this is yellow-colored LED supposed to be a visible-light LED or an infrared LED? It does not light up when I use my multimeter diode test. It also does not show up on my smartphone camera, which captures infrared from remotes etc. So either it is broken or it requires more voltage than my multimeter diode test provides.

 I just guessed infrared because the detectors have this dark look that reminds me of an infrared filter. But I also opened up my working USB zip drive and it shoots visible light at the reflective spot on the disk after insertion.

Edit: I replaced the LED by a red 3mm LED and it worked! The drive now accepts 250MB media again. Even though it was not an SMT LED, a regular 3mm LED also fit there after removing most of the legs.