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TRS-80 Model 100 Floppy Drive 26-3808

M

MGaddict

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Joined
Nov 25, 2017
Messages
22
Location
DC area
I recently obtained a Model 100 and a portable floppy drive CA# 26-3808. The problem is, that's all I have. I need the serial cable to connect the two. I don't mind trying to make one if somebody knows the pinout of this odd 8pin RS-232C connector on the back of this drive. I found the technical manual that lists pins 1 through 8, but I don't know which pin is which.
1 2 3 4
5 6 7 8
or
1 3 5 7
2 4 6 8
or
4 3 2 1
8 7 6 5
I really don't know.

I've been searching online for days and can't find a replacement cable, unless somebody knows someplace cool to look.

The next problem will be to find single sided 100k disks and the dos install disk this was supposed to come with. I'm hoping I can get that from club100 or something.
I have a Serial to USB cable which works pretty well. I just want the floppy drive to work because I have it. It powers on and sounds good. But that's as far as I've been able to test it.
 
It's not just an ordinary cable; it has several passive components to convert TTL to bipolar RS232. The details are on line somewhere but I can't find them off-hand; why not ask on the Club100 list, I'm sure someone will know.

https://bitchin100.com/

Folks there will also be able to help you with the boot disk; if you can't find DD disks you can probably get away with HD; they're all double-sided.

m
 
The pinout is as follows (viewed looking into the pins on the back of the drive):

7 5 3 1
___-___
o o o o
o o o o
-------
8 6 4 2


1 - GND
2 - CTS
3 - DTR
4 - RTS
5 - DSR
6 - TXD#
7 - RXD#
8 - n/c
 
When trying to get my drive working, I noticed that the rubber drive belt had gone soft. This drive belt measures 0.125" wide and has a circumference of 9.625". Going about 5% shorter for proper tension, this means the drive belt should be 9.2" long. I found a replacement here which I will order and try out.
 
WOW! I have to say thanks. I found this forum from VWestlife's youtube channel and this is so much better than I could imagine. ejs, thanks. It'll probably be next weekend before I have time to try this, but I am completely up to giving it a try. Did you make one of these cables yourself? I've made up cables before, but this'll be a bit more advanced than anything I've made before, so I'm completely looking forward to it. Thanks again for the resources.
 
The belt from turntableneedles.com arrived. It works great.

To boostrap the system, I used DL-ARC.EXE from http://www.club100.org/catalog.html. I had to run it on an old Windows XP system to get it to extract the files. There are two programs, Teeny and Desklink. Teeny (once set to 9600 baud) was able to transfer DOS100.CO/DOS100.BA as well as FLOPPY.CO to my Model 100.

Both DOS100 and FLOPPY were able to talk to the Tandy portable disk drive. I was able to format a disk and store a few things on it. Desklink emulates a floppy so it's a good way to transfer data from a more modern PC.
 
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