Wanted: Upgrades & Extras for my TRS-80 Model 4 and Tandy TRS-80 Model 4D

[dracos]

Here is what I currently have, or have coming and what I would like to find:

Model 4 (64k) (haven't checked whether gate-array or not) 2x SS 5.25" drives, nothing else.

Model 4D (64k) 2x DS 5.25" floppy drives, 2x DS 3.5"(external) floppy drives, 15mb external HD (on the way).

Looking for:
Model 4 Grafyx Solution
Radio Shack Model 4 high-resolution board
The Deskmate software that was released with the 4D.
8x or 16x MN4164P-15A ICs for upgrading to 128k
128k case badge(like my avatar), oooo
Just about any parts/pieces you might have in a pile, especially some spare floppy drives to refurbish for eventual replacement would probably be a good idea.

Anything you know about that I haven't mentioned, and probably don't know about!
Suggestions and info regarding the same, also appreciated.

 

[Chromedome45]

Did you get the 15Meg HD yet? Also finding the hires boards is going to be nearly impossible. And if you do find one be willing to fork over a few hundred dollars! I sold one to a guy in Australia and he paid $200+ for it. To upgrade a Model 4 to 128k your going to need a special PAL chip. Also hard to find. The 4D should be a lot easier to upgrade to 128k though Moving a jumper I think. Good luck hunting these down.

 

[dracos]

15 meg is on the desk, though I have yet to fire it up, probably tomorrow.

Didn't know the 4 would require an additional chip. PAL? Anyone got a part number on that?

Thanks!

 

[Chromedome45]

Yes it's a dreaded PAL chip. it's kinda like a special PROM device. It replaces the Shunt in U72 that's in there now. Can't remember part number off hand.

 

[dracos]

Well I wanted to edit my original post but I don't see an edit option any more?

Update:

Acquired 15meg HD, have a beat up 35meg untested, and just picked up a 5meg with a bundle.
So should be good on HDs, though if someone has an unwanted housing even if internals are dead, I would not mind having.

4164 drams are on the way, no good on those.
So now I need a PAL chip also for the 4.

I also need a longer ribbon cable for my external 2x 720k floppies.
(need to go back and count conductors, should be std 34, yes?)

 

[Chromedome45]

34 pins yes on the floppy cable. And need to make one of the 3.5's Drive 0 and one drive 1. Hopefully you have older 3.5's where you can still set the drive ID's.

Check this old post: http://www.vintage-computer.com/vcforum/archive/index.php/t-18482.html

 

[Knuckledragger]

Hi, I realize this post is a few months old but I only subscribed a couple of weeks ago so I am cramming on a lot of stuff trying to learn what to do concerning some problems I have. I ran across this while searching around for stuff on memory upgrades and other stuff. In case you still do not have that number on that shunt part it is listed in the Model 4 Technical Reference Manual on page 5 it is the procedure for upgrading from 64k to 128 k and is as follows:


1.3 JUMPER OPTIONS

1.3.1 16K to 64K
1. Remove U77-U84
2. Move E5-E6 to E5-E4
Move E1-E2 to E2-E3
Move E12-E13 to E12-E11
3. Add E7-E8 and eight Tandy #8040665 ICs in
locations U77-U84.
4. Remove capacitors 068, 072, 076, 080, 084, 088,
092 and 096.

1.3.2 64K to 128K
1. Remove shunt at U72 and add IC Tandy
#8075468 in its place.
2. Add eight Tandy #8040665 ICs in locations U85-
U92.
1.3.3 Graphics Board
1. Remove E14-E15 (and screws near U65 and
U71).
2. Plug in Graphics Board
3. Replace mounting screws at U65 and U71.
1.3.4 E9-E10 are not used at this time

However I ran across the installation instructions for the procedure online which are more detailed than the Tandy manual instructions above. The sad part is that they are from a guy Stan Slater (who passed away) who started the site Computer News 80 to fill the void left when Micro 80 stopped writing about the TRS computers in order to focus only on the Tandy DOS line. He sold the kits for this from the site for years.

I think the pages I found are cached because there have been no updates for several years it appears nobody has carried on his work. In those instructions he states how to tell the difference between the non- Gate Array Models and the ones that are. He also further states that ALL Model 4 units were shipped as Gate Array; however, there is a bit more involved than simply moving a jumper even on the Model 4D in that you do have to be proficient at solder tinning as the move requires that expertise unlike simply moving a JUMPER on a later type of board. He also included a diagnostics disk to test the upgrade with to ensure its success.

I think this is what you are referring to. If not, well no harm no foul and I learned something myself. However, I was wondering where you were able to obtain the chips from. I have looked but had no luck as of yet finding them much less the PAL. In fact according to Mr. Slater in the document I downloaded he stated that the PAL Chips he had were the last supply manufactured for Tandy and were the original parts.
As I said I hope this helps; if not you than maybe somebody else on down the line.
Cheers to all, Gordon

 

[dracos]

This project has been sitting for a while, but hopefully I am ready to get back to it, soon. I have two 4s and two 4Ds, one of each being fairly pristine, the others being in what looks to be decent condition, needing a good going through and testing, at worst, good parts boxes.
I have the appropriate chips and what I think is a capable PAL programmer, and a jedec file that should do the trick. Just haven't had time to properly dive into it. If successful I hope to be able to provide the requisite PAL chips for non gate array folks.

Thanks for the info!