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Ok here is a "WHY" or can it be done question

Eudimorphodon

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I can't imagine why *not*, if the chassis is from a non-Gate-Array one (isn't the back panel different on the GAs?), but I've never taken the two apart so no idea if there's some gotchya like different cable connectors, etc. IE, I'm pretty sure the basic form factor of the motherboards was the same and that there wasn't anything "special" about the Model IV boards that were used for III upgrades, but I don't know if said upgrades came with any adapters/brackets/etc. to work around differences in the native chassis.

Obviously if you retained the IV keyboard it'll have extra keys that wouldn't get used by a III, although you might be able to PEEK for them in the matrix.
 

Chromedome45

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Yep it would be for a Non-Gate if I did it. From what I can see in pictures the connectors for power and video appear to be in the same spots. Same with the keyboard connector. Plus the Floppy controller and RS-232 are identical. And yes the "GA"'s have the RS-232 pointing out the back. The NGA RS-232 is pointing downward. Oh and the Keyboard would loose some of it functionality mainly the "Function" keys which don't do much anyway.
 

leeb

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Cant think of why you would want to, but they should be a mechanical perfect fit. After all, the 4 was built off the III and I doubt anything about the case was changed except for badging...

Still trying to come with a 'why' tho... :rolleyes:

('Why Not' is a copout... 'My III needs a new case' is FAR better. :p )
 

barythrin

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Did you see that someone recently had a huge supply of systems for sale and one was a model III or 4 in a model 1 body?
 

Eudimorphodon

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Did you see that someone recently had a huge supply of systems for sale and one was a model III or 4 in a model 1 body?

I can't imagine a real Model III/4 board fitting in a I, however, there was an outfit that sold a Model III compatible motherboard replacement that fit in a I's case. (Supposedly it had a disk controller and everything on it? Ads for it appeared in 1985-ish era 80 Micros.) Was it one of those by any chance?
 

TRS-Ian

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The III board will fit in a 4NGA but take note of the following:

The you need to take the L-O-N-G cassette cable from the donor III as well as the short one from the 4NGA won't reach.

The 4NGA has its cassette port on the right-hand side (when looking from behind the computer with the lid off) whereas the III has the cassette port on the left hand side next to the keyboard connector. The 4NGA has a sound port next to the keyboard connector which will not be used on the III motherboard.

The rest of the connectors should install OK.

Ian.
 

Chromedome45

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Now that looks cool. I think I actually heard of it. Someone did post about one a while back. There was something odd about the part number started as 11-xxxx when all trs-80's started with 26-xxxx But still neat looking!
 
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billdeg

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thm_TRS80_Model-4_FCC.JPG

Pic of what you might call an engineering sample Model 4, submitted for FCC testing before being moved into production. Note how keyboard is not like the model 4 keyboard. Other than the color, it's the same as the Tandy 3 keyboard in the video posted on this thread. Very interesting. The Tandy 3 case was probably used to house what was then the new TRS 80 Model 4 submitted to the FCC. Agree? Note the odd-looking display is a glare guard added by Roy Soltoff after the machine was returned to him from testing. I think he also added the 128K sticker and maybe the TRS 80 Model 4 sticker some time afterwards as no other labels/serial numbers are present on the system. He kept the unit and used for a number of years afterwards. He gave it to me in 2005. Given this was a personal system, he may have developed and tested some or all of LDOS on this as well...you never know. I remember when I went to his house, his car's vanity license plate was "LDOS"

thm_MB_rear-middle.jpg

Motherboard Rev "N/C"

thm_tandy_model4__FCC_underside_fccwarn%5B1%5D.jpg


http://vintagecomputer.net/browse_thread.cfm?id=23
More pics/info
 
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Eudimorphodon

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Here's the link on cctalk to the person selling the trs-80s in VA. This is his reply that I missed about his Model 3 in a model 1 body (I'd love to save it or buy it just to see it lol but I don't have the resources right now and I'm not sure if he's willing to ship in the US). Either way, heads up that if you're in the VA area he has quite a few systems he's looking to sell or offload.

Yeah, that sounds like the motherboard upgrade kit that I remember seeing in an 80 Micro but can't remember what month. (I quickly scanned through a couple on Archive.org and failed to find it, I wonder if Tandy sued them shortly after an initial run.) On one hand it almost sounds like a bit of a waste of a Model I, since all you're using is the case and the keyboard (and I imagine you'd have to modify the keyboard to make it 100% compatible, since the I and the III mapped the shift keys slightly differently), but on the other I think it only sold for around $300, which if you still had a cassette-only Model I in 1985-ish might have made it cheaper than finding an expansion interface and double density board. (A new one, anyway.)

It would certainly be neat to see the board and see if it looked simple enough to clone, since what the world really needs is a new-build TRS-80 replica! Alas VA is a long way away.
 

Chromedome45

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I like the white keyboard and that prototype bill look really cool. I sent an email to Roy and he said I could have it! So give it up...Ok I am obviously joking here but very nice of him to give it to you. Probably a whole bunch of cash if it were to be sold.


And off topic on the Model 3 in a 1 case. I had at one time thought about putting Model 1 in a Model 4 or III case as well. But the physical fit of having to put in the Model 1 board and the Expansion Interface seemed like it wouldn't fit to well not much space in there.
 
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billdeg

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I had plans to demo the Model 4 at VCF E last year until it was cancelled, maybe next year. I just finished going through it and cleaning it up, the drives needed a little work.
 

Chromedome45

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Yeah those 5.25 full heights are near the end of there lives. I had one working nearly perfect this morning. Now it won't even verify after format no matter which disks I use and after a good cleaning of the read/write head. So had to put in my spare MPI 51. Now it looks like your prototype there. MPI in bottom drive slot and Texas Peripherals in top drive slot.
 

billdeg

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Has anyone done any research into these Texas Peripheral drives...? I have a box of them that are bad or flaky. Fortunately I usually can dig up a replacement. Tandons and MPI's have held up better over time so I tend to replace the TP drives with *anything* else. My guess is that there are one or two common faults with the TP's, never spent too much time on them to find out. I really should see what can be done, it's a waste to have so many that don't work correctly..

[update]..Looked around, including threads here that Chromedome45, etc have been in...It ain't easy to fix the TP drives, too many mechanical failures, most people replace with a different type of drive (5 1/4", 3.5", HDD, etc).
 
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billdeg

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[update #2] - on page 81 of the Radio Shack Model 4 and Model 4 Gate Array Service Manual there is a tech specs and diagnostic check out procedure that describes how to service the Mini Disk Drive. The board layout in the schematics is a standard issue Texas Peripheral 5 1/4" drive. I double checked to be sure.

So..this means that you can at least have a fighting chance to repair a TPI disk drive by using the Service Manual. You'd need an oscilloscope and a lot of patience etc. but at least you'd know exactly what was wrong. makes it easier to merge two bad drives into one good one.

Ebay just sold a Service Manual- auction 200916084649 for $40, but I bet if you look you can find a PDF someplace.
 

Chromedome45

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Oh I have PDF's of the Tech Manual for Model 4 dated 1983, One dated 1985 that mainly deals with the Gate array version and a Model 4p tech manual. Regrettably I sold my tech manual a few months back.

I have been using them a lot lately to fix my Non gate array which has a nagging video problem. Sometimes get a clear screen sometimes filled with garbage. so still fighting that issue. Thought I had it fixed but it keeps coming back. I think it's haunted.

As far as drives go get a couple of good half heights and use them. Or do as I did on my Gate Array replace with 3.5" drives.
 

Agent Orange

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Oh I have PDF's of the Tech Manual for Model 4 dated 1983, One dated 1985 that mainly deals with the Gate array version and a Model 4p tech manual. Regrettably I sold my tech manual a few months back.

I have been using them a lot lately to fix my Non gate array which has a nagging video problem. Sometimes get a clear screen sometimes filled with garbage. so still fighting that issue. Thought I had it fixed but it keeps coming back. I think it's haunted.

As far as drives go get a couple of good half heights and use them. Or do as I did on my Gate Array replace with 3.5" drives.

Have you tried some freeze spray on that monitor? http://www.alliedelec.com/chemicals/freeze-sprays/
 
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