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Tandon floppy drives and brittle plastic latches

F

Fractal Fischer

Member
Joined
Apr 17, 2018
Messages
10
Location
Frisco, TX
Hi all,

I'm quickly finding out with my recent repair attempts on an IBM 5150 that the plastic holding the front latches on Tandon floppy drives is evidently about as brittle as the Dead Sea scrolls.

The PC's been sitting untouched in a dark air-conditioned closet the past 30 years, and even so the latching mechanism on one of the floppy drives more or less disintegrated on the first or second use. I bought a replacement Tandon TM-100 that looked to be in good condition, and almost instantly the plastic latch shattered and failed in the exact same way as the first:

20180928_090850 (Large).jpg

I ordered a yet another replacement just a moment ago (you can never have too many spare parts, right?), but before I even so much as breathe on it I want to figure out if there's anything I can do to prevent a repeat of the last two breakages. I've had good results restoring light plastics with the retro-brite solution but I'm sure it'd be a pretty bad idea to use a bleaching agent on a black bezel. Any suggestions or should I just go ahead and get the super glue ready?
 
Those Tandon drives need to be closed carefully, because a lot of pressure on the hinge
when closing with the floppy inserted can break the plastic. Likewise, I don't let it flip
open with a snap, as I retain the operating hinge part so it doesn't bang.

Yes, there is a FIX. If you look closely at the hinge points you will see that there is one 1/8" brass rod
that is shown on your photo. The other hinge point is made up of two small white nylon pins.
These pins stress the plastic and it breaks. I purchase some 3/32" Brass (K&S) rod and replace the
two white pins with a full length piece of the brass. (You need to measure the pins to be sure they
are 3/32" because I'm going from memory now since I'm not at home.)

The broken plastic part has been drawn in CAD and the CAD part made into a 3D Object. I've got a few
of the test parts that have been printed on a 3D Printer, but haven't tested then yet. I believe they will
work, but they may need a bit of modification. When I get the time to test a part and know they will
function, the package is going to ThingIVerse. But, for the time being I'm at a standstill until I
know the parts are accurate enough to use.

The printed parts should be a long term fix.

PM me if you want one to test with.

Larry
 
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Those things would break even when they were fairly new. I have a machine with a pair of tandon drives that had a note inside it stating that one of the drive latches had been repaired back when it was in use. And sure enough, the A: drive had a different latch style.
 
SomeGuy,
I think your response is correct for any Tandon with the White Nylon Pins, but it does not apply to floppy's with the two brass full
length rods. I've got several Original Floppy Drives with Brass Pins that are 100% functional, with original parts.


Larry
 
Below is a shot of a TM-100-4 drive with my own repair. Basically 0.025" brass sheet and brass rod. Works fine and took very little time to fab. It'll probably last until the drive falls to pieces.

bracket.jpg

FWIW, the drive has a manufacture date in mid-1981, so it's older than your 5150.
 
ldkraemer said:
Those Tandon drives need to be closed carefully, because a lot of pressure on the hinge
when closing with the floppy inserted can break the plastic. Likewise, I don't let it flip
open with a snap, as I retain the operating hinge part so it doesn't bang.

Yes, there is a FIX. If you look closely at the hinge points you will see that there is one 1/8" brass rod
that is shown on your photo. The other hinge point is made up of two small white nylon pins.
These pins stress the plastic and it breaks. I purchase some 3/32" Brass (K&S) rod and replace the
two white pins with a full length piece of the brass. (You need to measure the pins to be sure they
are 3/32" because I'm going from memory now since I'm not at home.)

The broken plastic part has been drawn in CAD and the CAD part made into a 3D Object. I've got a few
of the test parts that have been printed on a 3D Printer, but haven't tested then yet. I believe they will
work, but they may need a bit of modification. When I get the time to test a part and know they will
function, the package is going to ThingIVerse. But, for the time being I'm at a standstill until I
know the parts are accurate enough to use.

The printed parts should be a long term fix.

PM me if you want one to test with.

Larry
Click to expand...

No way I can turn down an offer like that. I'd be happy to test and give feedback on any parts you'd care to send. I'll shoot you a pm here in a bit.

The new replacement drive just arrived a moment ago and it turns out it's actually a model TM-101, which appears to have a redesigned latching mechanism (pictured below). I can't seem to find any real comparisons between this model and the TM-100, but it looks to have done away with the nylon pins and looped plastic that failed in the other drives. Does anyone know if these units are any more or less prone to breakage?

20181002_155322 (Large).jpg
 
Andrew
Your package is on the way. USPS Tracking Number
9500 1154 1872 8277 0556 18

Should arrive Tuesday 10/09/2018 $3.50

I measured the bit I used to drill the hole and it was .096"

You need to purge your PM's

Here is a Photo of the part I'm going to install.

P1030880.jpg

Thanks.

Larry
 
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Fractal Fischer said:
No way I can turn down an offer like that. I'd be happy to test and give feedback on any parts you'd care to send. I'll shoot you a pm here in a bit.

The new replacement drive just arrived a moment ago and it turns out it's actually a model TM-101, which appears to have a redesigned latching mechanism (pictured below). I can't seem to find any real comparisons between this model and the TM-100, but it looks to have done away with the nylon pins and looped plastic that failed in the other drives. Does anyone know if these units are any more or less prone to breakage?

View attachment 48411
Click to expand...

If you're going to to use that TM-101 on your IBM 5150/5160, I think you've got a small problem. The PC and XT use 48 tpi drives (i.e. TM-100-1 or TM-100-2); you show a TM-101 with a 96 TPI sticker on the door latch. That means that you have a -3 or -4 (96 tpi) drive. It's not going to work with normal 48 tpi recorded floppies without some software intervention.

At least you don't have a -4M (100 tpi)...
 
Chuck(G) said:
If you're going to to use that TM-101 on your IBM 5150/5160, I think you've got a small problem. The PC and XT use 48 tpi drives (i.e. TM-100-1 or TM-100-2); you show a TM-101 with a 96 TPI sticker on the door latch. That means that you have a -3 or -4 (96 tpi) drive. It's not going to work with normal 48 tpi recorded floppies without some software intervention.

At least you don't have a -4M (100 tpi)...
Click to expand...

It is indeed a -4, and this is definitely good to know. I had my suspicions just based on the fact that I got it for next to nothing despite apparently being NOS, but my practical experience up to this point only really goes back to about the 386 era so some of these things are still a bit esoteric. Look like I need to do some more reading. Thanks for saving me from an afternoon of needless troubleshooting. Hopefully I can still fix the broken latch on the one of the other drives though using ldkraemer's solution.

Now that I think about it though, I wonder if I could use the latching mechanism from the 101 to repair one of the broken 100s. Seems like it might be similar enough to fit. That is assuming it can survive being dismantled without disintegrating to dust like the other two...
 
Andrew,
I've installed a 3D printed part and the 3/32" Brass Rod in my Tandon TM-100. I tested the Floppy to make sure I could format it
with no errors, and that a file copied there could be edited. Everything seems to be fine with one small thing that needs updated.
The Mount holes in the hinge part need to be elongated about .3mm in the direction away from the Brass Rod Hinge Pin. That will
allow the complete Door assembly to be finely adjusted so the Hinge Door is flush and even with the Front Face Plate. I used a small
grinding stone in my Dremel to make a slightly elongated hole. That fixed the problem. The CAD drawings are being updated.
(The Mount Holes are the ones that are closer to the read heads when the Door is in position.) I've added a Photo with WHITE lines
where the holes may need a bit of elongation.

I'm satisfied with my drive as being operational with the new part. You can take a small round file and elongate those holes
a bit if needed. Be sure to just snug up the door and fingers that barley miss the floppy and test the door operation and if it
is Flat and Flush with the front face before tightening the screws.

I'll get Thing-I-verse updated when I have the new files.

Larry

Update.jpg
 
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Andrew,
I recently located a Tandon TM-100-4 that had a bad hinge (had the white nylon pins) and I replaced it with a 3D Printed
Part (with ver1 modification) along with the 3/32" Brass Rod. I got the Door flush with the Face Plate, with the metal floppy
position fingers adjusted correctly.

The floppy formatted correctly when attached to my Model 4 with a DS 80 Track Floppy configured.
That now makes two floppy drives I got working again. Your Floppy Drives should be back in running order too.

Larry
 
I'm happy to report two drives repaired with everything lined up flush on the first try. The repaired drive actually seems like it's working more smoothly than the one that never broke (yet). Thanks again for all the help on this.
 
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