Resurrecting Model 1 floppy drives - my turn.

[syzygy]

It is finally time to do something with the TRS-80 “stuff”. The goal is to get one system working with the expansion interface and two drives. A bonus would be a second system with just a tape cassette. So, I am trying to resurrect four 5.25” floppies. I know that two of these (Shugart, SA400) worked back in the day, but I am just not sure about the other two (MPI, B51 and Tandon, TM100-1).

Here has been my approach. Comments and pointers are very welcome.

I found manuals for the drives and read a good portion of them. Read relevant threads on this board and elsewhere.

Opened each drive up (last used 30+ years ago, by me, or whoever gave one to me) and…

First looked them over very carefully to spot obvious problems like cracked power cords.

Used plenty of canned air, “duster”, but not too close to any components. Open surface areas cleaned with a little Windex on a cloth.

Used plenty of non-residue electronic cleaner on all of the connectors – pulling apart and spraying both ends. Used Isopropyl alcohol on them and also Deoxit-gold.

Used isopropyl alcohol on the head…gently.

Took a picture of the terminating resistors (or socket) and the shunts.

Example here is of the TM100. Note that the 150 ohm resistor pack is only 14 pin and is in a 16 pin socket. Didn’t have a 150, but did have a 330, so I used that and made a note. Also, it looks like a staple was used in the shunt socket – hey back in the day, you used what you had



Noted Mouser numbers for 14/16 pin replacements [ 652-4114R-1LF-150 / 652-4116R-1LF-150 ] and suitable dip shunts [I think 571-18251907 will work] in case I want to get “proper”.

After a smoke test, I used a little break-out rig where I could get access to some drive signals.



I was successful in turning the motor on and checked timing using the strobe disk.

Moved the stepper (and direction signal) and noted that the Track 0 signal worked. Probably not a good idea to be bouncing the stepper around, but it seemed acceptable for a quick test.

Checked that the sector index signal worked (more or less – i.e., it flashed an LED).

So far, all four have passed!

Until I get my Greaseweazle, this is all I can think of to do, but I am cautiously optimistic that these drives may actually have some life in them.

 

[ldkraemer]

For the Tandon TM-100-x Drives you need to do the following:

1. Open the Door and look at the Hinge Point for the Door. You are looking for a full length
piece of 3/32" brass Rod, versus two short White Nylon Pins. If you see two short White
Nylon Pins they need to be replaced with the Brass Rod. You also will likely need a new
Hinge Part to replace the Broken one. Hinge Part Photo Attached (Should also work on the
Shughart.)

2. Be sure to look at the RPM Board on the Back of the Tandon TM-100-x. The two caps
are bad about leaking their acid on the RPM Board and this eats away the PCB Traces.
It might be a good idea to replace them before they eat your PCB traces. If the PCB
traces have been removed I can rebuild your RPM board with Copper Hollow Rivets
and a few pieces of wire wrap wire, and test the RPM Board on my Tandon Drive.

3. Wipe the Tandon TM-100-x Head Guide Rod rails with a cotton swab sipped in Alcohol.
Then lubricate those Head Guide Rod rails with Dri-Slide, a Motorcycle cable Lubricant.
It does not attract dirt and will last for years. Available on Amazon or any Motorcycle shop.
Also makes the drives a lot quieter when they step. (Works good on Scanner Rails.)

4. For the Drive Select Shunts, get yourself some 7 Pin or 8 Pin DIP Switches and insert those
in the IC Sockets. Now, you can easily select what drive you are wanting.

5. You ONLY need the Terminator (PULLUP Resistor) on the Floppy Drive that is the last one on
the End of the cable.

For the Model 1 you need a Special Boot floppy for Drive 1. Track 0 is Single Density. You can
make that Boot floppy with Debian (Linux) and a 180K SS/DD Floppy Drive. (What OS are you
planning on using? TRSDOS, NEWDOS80, LDOS, Other?

You need to start by playing with the TRS-80 (Model 1, 3, 4) Emulators, while you are getting the
Model 1 functional. The Emulators available are David Keil's Emulator (TRS80), Tim Mann's
(XTRS), Jen Guenther's (SDLTRS), Matthew Reed's (TRS32), and George Phillips TRS80GP.

trs80gp - A TRS-80 Model 1,2,3,4,12,16,6000,MC-10,Color Computer,DT-1,Videotex Emulator

48k.ca

David Keil's TRS-80 Emulator Page

Lots of good software for the TRS-80's.

You will also want the TRSTOOLS Software, to open file images and extract/insert files.

The *HUMONGOUS* CP/M Software Archives

The Internet's largest, most comprehensive collection of software for Digital Research's CP/M family of operating systems.

cpmarchives.classiccmp.org

The *HUMONGOUS* CP/M Software Archives

The Internet's largest, most comprehensive collection of software for Digital Research's CP/M family of operating systems.

cpmarchives.classiccmp.org

https://willus.com/trs80/

http://ts-inc.dyndns.org/Diagnose%20Repair%20TRS80%20TRS-80%20Model%201.html

David Keil's TRS-80 Emulator Page

xtrs: TRS-80 Model I/III/4/4P Emulator for Unix

Jens Guenther / SDLTRS · GitLab

TRS-80 Model I/III/4/4P emulator SDLTRS/SDL2TRS focused on EACA, Prologica, TCS and other systems

gitlab.com

System 80/TRS-80 Model 1 Disk Software Archive

Larry

 

[syzygy]

Thanks so much for taking the time to respond. I read all of your message and bookmarked it for future reference. I really do appreciate the effort. Just wanted to acknowledge a couple of points....

On the two caps that can be problematic. Am I right that you mean these two on the servo board?

They look fine but they are easy enough to replace.

As an aside, when I opened the Tandon TM-100A, I immediately saw a telling stain on the inside of the case. I cleaned it off, but you can still see it here.


The stain was immediately adjacent to the 3300 uf cap on the PS board.


I believe that the entire board was replaced and that the large cap had blown at one time and was sent out for repair. Note that the board looks fine but the mounting screws are longer and mismatched. Note also, what looks like, a repair sticker. Additionally, see all those drilled holes in the case? - somebody wanted to increase the venting. Now, I know that I did not do any of that, even though this was back in ~1984 [the drive has a 1982 manufactured sticker). I would have remembered. It could have been working after the repair and when given to me as I put a note on it (in my handwriting) about the drive selection.

I have had large caps blow on me before and it is a memorable sight and smell.

My door is the frail one, from your description - good to know.


I have a number of lubricants and would likely have used a small amount of lithium product. After your response, however, I placed a bottle of Yamaha lube in my Amazon list ($10) . Reading up, this molybdenum grease is widely recommended - would not be bad to have some on hand.

I have probably 100+ TRS-80 M1 and M3 5.25 disks. I used TRSDOS and NEWDOS and RS Edt/Asm and Mzal and some really nice disk utilities. Add to that some IBM PC ones and a plenty of C64 formatted ones left from my divesting a while ago. Add to that ~100 of the 3.5" PC ones. I know I have some 3.5" drives (720/1.44) and at least one 1.2M 5.25 drive, somewhere.

The only think I would push back on (and respectfully so) is the simulation stuff. I am not at all interested. I have never even used Proteus. Yeah, I know - a lot of folks find them very valuable and maybe one day I will change my mind, but not today. I admire the coding, but they are not for me.

I am anxiously awaiting the Greaseweasel and hoping that I can both get these (and the other drives) working and go from there.

Again, thanks much, I am sincerely appreciative..

 

[ldkraemer]

Dri-Slide isn't molybdenum grease or Lithium Grease. It is a Liquid that drips on the Head carriage
Guide Rods. You don't want Grease on the Guide Rods as they will attract dirt and make the head(s)
step harder not easier. Dri-Slide or Graphite is the best way to go. Or a dry spray lubricant with PTFE.

Yes, those are the Caps. If they haven't leaked, just keep an eye on them, because if they leak,
the acid will eat up the PCB traces. I think they are 16 volt 47uF if i remembered correctly.

Send me an Direct Message and I will send you a Brass rod and hinge part to repair your door. I just resin
printed a new batch of Hinge parts. I also have a document that explains exactly what needs to
be done to keep from causing damage to the read head(s). It's an easy process, but you need
to still be aware of a few things. You can keep the existing hinge part as a SPARE. You won't
break the Tough Resin one I send. Hundreds are out there working on drive with not one
negative report as of today.

Larry

 

[syzygy]

Hmmm maybe I read wrong or looked at the wrong product, but I thought that the Drislide adverts clearly state Molybdenum Disulfide, https://cdn.shopify.com/s/files/1/0095/7332/files/TDS_MultiPurpose.pdf?8320760919139410357 as well as in the MSDS https://cdn.shopify.com/s/files/1/0095/7332/files/TDS_MultiPurpose.pdf?8320760919139410357. Maybe, I should have said Molybdenum Lubricant and not Molybdenum Grease. Anyways, thanks for the tip and the kind offer - I''ll let you know if I get that far. -Cheers

 

[syzygy]

So, I have now gone through all four drives and, to the extent that I have tested them, they work!!

I spent the most time on the MPI, B51. This is not a bad drive and does MF and MFM and I have been able to read 35T SSSD and 40T SSSD and 40T SSDD (based on my TRS80 M1, M3 and IBM PC disks). Have not done any real writing except from a C64 disk. In all cases (mostly .img) I can browse through the file and recognize stuff that I wrote 35-40 years ago and that has been a lot of fun!

The drive had some funkiness to it.


It has some thick foam that was degrading and flaking. I removed it and replaced it with new foam rubber.



The gold cables are practically sitting on the PS. But, I can see holes on the frame where I would expect to see a bracket. Maybe this was an after-fit or something - I don't know and it was probably just given to me and I said thanks. I can'At remember.


I could have just connected the twisty cable directly, but decided to see how this cable would work. First I notice some tearing and after noting that it was on interface line 2, which is a spare, I just taped it up...as well as where the cable sits on the frame bottom.

I also had to key the drive to make it compatible with the cable I am using (an IBM style twist). Amazingly, I managed to do it without damage


So, it is back in service.

I even managed to find some floppy drive cleaners - three of them including these two - one of which was unused (still had cutouts attached.).





The solution (IPA) had evaporated as you might expect. These have come in handy because many of my old disks are not clean.

As far as how the project is going? So far so good.

 

[ldkraemer]

They seem to match My Model 1 AeroComp Drives, except that mine are oriented
such that the Power Connector is Down and the data connector is Up. That keeps
the data cable away from the frame damage. Plus, the Floppy is oriented properly
when inserted.

You may want to Rotate the Floppy 180 Degrees in the case to prevent future problems.

Larry

 

[syzygy]

Some 10 months later, I did something (not much) about this funky drive. First, you are correct @ldkraemer and according to the manual, this drive is not meant to be mounted in the vertical orientation. Back in the early 80s, there were lots of OEMs who sold drives and maybe they did it, or maybe the drive was repaired and they did it - who knows, but it came to me that way. I did get it up and running but that cable bugged me. The case was also beat up pretty badly and I thought I would take a shot at doing some refinishing (something I have very little aptitude for).



I used to plastic clips to help route the cable away from the transformer.. The larger clip in the rear of the picture keeps it folded and away. The small one at the bottom of the pic keeps it from direct contact with the transformer. I mounted the connector on the outside of the frame such that the connecting cable fits all the way on.




I sanded the case and did what I could to reduce all the bends and deep nicks. Then, I tried to paint it and it was an embarrassing mess and the pic is being generous. That stuff is tough for me....maybe someday I will get better.

It's back in service and it still works and nothing is melting or igniting. I feel like I made some improvements, but didn't really "do it right". Nevertheless, it is off of the list.

 

[ldkraemer]

The Photo looks nice to me. Reminds me of my Model 1 that I need to get running again.


Larry