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Docs needed for TRS -80 Model II Disk System

C

clh333

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Cleveland, OH, USA
Having just acquired the above-mentioned disk system, complete with cable and two drives, I am now faced with figuring out what is in it, how it operates, what can be connected to it and what to look for before I power it up.

Documentation, as it is commonly known.

Anyone with information or practical experience willing to offer advice or guidance will be greatly appreciated.

Thanks,

-CH-
 
Thank you for this information. After reading the DS documentation I have a couple more questions:

Do you know who sourced the drives? I read somewhere that they were CalComp.
Do you know whether the disks (Catalog 26-4905) are hard or soft-sectored?
Can the system be interfaced with any of the other TRS-80 machines, e.g. Model III, 4, 12 or 16?

Thanks again,

-CH-
 
> Do you know who sourced the drives? I read somewhere that they were CalComp.

Peter has some information on the drives here:

https://pski.net/trs-80-model-ii-family/

> Do you know whether the disks (Catalog 26-4905) are hard or soft-sectored?

They are soft-sectored.

> Can the system be interfaced with any of the other TRS-80 machines, e.g. Model III, 4, 12 or 16?

Any of those machines should be able to connect to a Model II via a serial port and a terminal program (the Model III's serial port was an add-on, if I remember correctly, the rest had serial ports built-in).

- Rick
 
Rick Thornquist said:
> Do you know who sourced the drives? I read somewhere that they were CalComp.

Peter has some information on the drives here:

https://pski.net/trs-80-model-ii-family/

> Do you know whether the disks (Catalog 26-4905) are hard or soft-sectored?

They are soft-sectored.

> Can the system be interfaced with any of the other TRS-80 machines, e.g. Model III, 4, 12 or 16?

Any of those machines should be able to connect to a Model II via a serial port and a terminal program (the Model III's serial port was an add-on, if I remember correctly, the rest had serial ports built-in).

- Rick
Click to expand...

Once again, thank you for this information.

Control Data supplied some of the expansion bay's drives, according to Peter's info:

"Tandy offered a disk expansion system which allowed up to 3 additional 8 inch floppy disk drives to be attached to the system. The expansion bay was outfitted with full-height Control Data Corporation (CDC) disk drives until late in the Model II run. As in the the computer itself, TPI drives replaced the CDC drives late in the Model II lifetime."

Shugart 800s were inside the Model II console, apparently.

Soft-sectored is good news, so is Shugart.

I regret that I wasn't more clear in my earlier question about interfacing: The expansion system has a 2x25 female connector at the end of a ~4-foot ribbon cable which undoubtedly connects to a Model II FDC. I am wondering if the Model II FDC was identical to any of those used in the other machines, or if an adapter, either passive or active, enabled the other machines to communicate with these drives in the expansion bay.

I have a Model III and IV; I don't yet have a II, 12 or 16. So the ability, or inability, to interface with any of these machines is a subject of interest.

Thanks again for your help.

-CH-
 
Gotcha.

I haven't tried interfacing the thing to a III or 4, so I can't help you there. However, I have connected it to a FDC on a Pentium PC. It's not a direct plug-in deal, though. The 8 inch disks require a separate signal that 5 1/4 inch controllers don't provide. It's called TG43 and it indicates whether the drive is on a track greater than 43. There is an interface that can handle this, the FDADAP, but I think it's for PC FDCs only (I don't know the III or 4 FDCs, so I don't know whether it would work with them). In my setup, it goes between the 50 pin cable that comes out of the expansion bay and a 34 pin cable that comes from the FDC on the PC.

This isn't exactly what you're looking for, but it might bump you in the right direction.

Here's more info on the FDADAP:

http://www.dbit.com/fdadap.html

- Rick
 
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Oh, and about the 12 and 16...

I actually don't know if the disk system will connect to the 12 or 16. There was a different disk system that attached to those machines that used double-sided drives (26-4165 and 26-4166). The Model II and the disk system used single-sided drives (26-4160, etc).

This is actually a good question. Does anyone know if a Model II disk expansion system will work with a 12 or 16? Peter?

- Rick
 
Thanks for your reply.

I recently began a project to rebuild a Shugart 850 and in support of that began acquiring materials; among them, an FDADAP from http://www.dbit.com/fdadap.html . I expect I'll be able to use it when communicating with the Disk System, with a PC or the Device Side Data FC 5025 http://www.deviceside.com/ sending the control signals.

I'm sort of following in the tracks of a lot of others on this site who have traveled this path in the past. The Shugart is my first venture into 8-inch territory and is unproven at this point but I have learned a lot from the experience.

Unfortunately that means asking a lot of basic questions.
Thanks for your help.

-CH-
 
there were two 8” drive makes used inboard to the model II: shugart and texas peripherials. all the model II’s were manufactured with shugarts, but some tpi went in as repair parts.

the TPI drives were clones of the shugart sa800. texas peripherals was owned by tandy/rs. they are equivalent practically speaking. single sided/soft sectored as rick said.

if you’re asking if you can use a model 3 or 4 fdc card with the model II, the answer is no. the model II technical reference manual is a very good overview. be aware that the schematics in there are early production. it’ll explain a lot for you.

the cdc drives in the external bay are notorious. tpi is much better and you will also see some shugarts in those bays. we treated shugart and tpi as equivalents for service purposes, though an attempt was made to swap like for like. if you have a bay with cdc drives, pay attention to the door close switch and pushrod assembly. i’m not going to say it was junk, but i’m thinking it.

the sa800 is an easy drive to work on and is a solid drive.
 
shank said:
there were two 8” drive makes used inboard to the model II: shugart and texas peripherials.
Click to expand...

I have seen 5.25" drives in some RS equipment (the Model 100 "DVI") labeled "TEC". Is that the same company with a different brand or another supplier?


shank said:
if you have a bay with cdc drives, pay attention to the door close switch and pushrod assembly. i’m not going to say it was junk, but i’m thinking it.
Click to expand...

As in: Press "up" (left) on the release at the "top" of the drive and the lower front drops "down" (swings right)? Hmmm....

All good information, thank you for your response.

-CH-
 
TPI did produce a 5.25" Tandon drive clone that went through various iterations--one being with the track zero switch glued in place instead of being adjustable. we had quite a time convincing them this wasn't such a good idea, but they finally relented. there were other running changes--but that's not about the Model II. anything manufactured by TPI is stamped TPI.

I don't think we're talking about the same CDC 8" drives from you description. regardless, they are delicate and lose alignment almost as soon as you finish with it.
 
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shank said:
TPI did produce a 5.25" Tandon drive clone that went through various iterations--one being with the track zero switch glued in place instead of being adjustable. we had quite a time convincing them this wasn't such a good idea, but they finally relented. ...
Click to expand...

Even I know that's not a good idea...

shank said:
anything manufactured by TPI is stamped TPI.
Click to expand...

I'm learning that Tandy had a wide network of suppliers.

shank said:
I don't think we're talking about the same CDC 8" drives from you description. regardless, they are delicate and lose alignment almost as soon as you finish with it.
Click to expand...

I may have a line on Shugart replacements. Any weak spots in the power supply? Weighs a ton and probably could light a city block.

Thanks again for the benefit of your expert knowledge.

-CH-
 
shank said:
CH

re: power supply. there are numerous threads here that deal with the MII ps. be sure to look them over. don't run it unloaded!
Click to expand...

Took a look inside. Pictures attached. Drives are Magnetic Peripherals / Control Data. SSDD I think. I misconstrued their orientation; top of drive is right, not left as I had assumed, so release is at the bottom, door is actuated with a spring-loaded rod as shank recalled. Space and power + data connectors for a third drive.

Turned the spindle by hand on both drives, heard a little clunking but things freed up after a few revolutions. Tried turning the stepper screw by hand but didn't feel right so I rotated it back. Inside the case is a thin layer of fine dirt / grit such as accumulates in an industrial environment. Astec PSU looks reasonably healthy for an old-timer but who knows.

This has a repair sticker from 1984 on the case and on the frame.

-CH-

IMG_3349.JPG IMG_3351.JPG IMG_3355.JPG IMG_3362.JPG IMG_3365.JPG IMG_3366.JPG
 
clh333 said:
This has a repair sticker from 1984 on the case and on the frame.

-CH-
Click to expand...

looks pretty good in there! definitely clean and get the grit off the worm gear before proceeding too far. some recapping on that supply, probably covered in other threads, and check the voltages. i figure you'd do that anyway. no adjustments on that supply.

what shop did the work? i probably know who last had their hands in there. :)
 
clh333 said:
See attached. Looks like Tony at shop 7130. Anyone you know?

-CH-
Click to expand...

I vaguely remember a Tony, but not sure what shop he was with. 01-7130 might have been the Cleveland shop--I think. I don't seem to have a service center list anymore--maybe someone here has come across one. We had techs (both male and female) we talked to all the time; some, not so much. There were around 150 company shops doing computer work (some with quite a few techs, but others as one tech shops), plus some full-line as well as franchise that push that number even higher. All company computer service centers handled in-shop and on-site component level service for the Z80 based systems and printers and on into the Intel years...
 
Completely disassembled the unit. I will be cleaning and testing the drives independent of the RS power supply, pictured below, which will need repair before I apply power. The 0.1 uf high-voltage paper-foil capacitor in the lower right shows cracks, for example, and for good measure I will replace all similar.

Would you replace ALL caps? Electrolytics don't display any signs of bulge or leakage, but I have no way to test them in circuit.

-CH-

PSU.jpg
 
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