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EOI: Model III and 4 hi-res graphics board reproduction kits

TRS-Ian

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Sep 10, 2011
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Hi everyone, I'm looking into which way to best support the TRS-80 with reproduction sought-after hardware and hi-res graphics boards are high up on people's lists.

I'm looking at reproducing the RS 26-1125 board for the Model III and Grafyx Solution board for the Model 4 and are after people's feedback.

They will not be cheap for me to make and sell, and for those who want to purchase a kit form, they will be complicated to build. An order of magnitude more complicated than the FreHD kits.

Eg. FreHD has 6 semiconductors, 26-1125 has 34 semis, and Grafyx Solution has 32 semis.

26-1125 works on the Model III and Model 4NGA desktop computer. Grafyx Solution works on all Model 4,4P and 4D computers.

Tooling up and parts inventory costs to produce these boards will be high for me in the short term, so I need to know realistically how many people are interested before proceeding.

Do people want to solder their own kits together or buy a pre-built unit?

Cheers,

Ian.
 

gp2000

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Vancouver, BC, Canada
I'd be willing to buy a Model III and a Grafyx Solution board if they're identical to the originals down to the last memory wait state.

A pre-built unit would be my choice. I'd like to believe that I'd be brave and purchase a kit (those '74 series chips aren't so intimidating), but I'm doubtful given the time involved. How long do you think it would take an amateur to solder a kit?
 

TheCorfiot

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South Wales, United Kingdom
Hi Ian

I would be interested in both type boards to include in all my future rebuilds and my own kit.
You know me by now however and i am happy to build them from bare boards.

Thanks for your ongoing support for the TRS80

;)
 

lowen

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Ian, have you considered the Model 4 Tandy hi-res board (26-1126)? It appears to have only 12 ICs.
One of those is a gate array, as I recall.

If the goal is full 'repro' hardware, that's a deal-breaker. Now, if using a modern FPGA or CPLD would work.... incidentally, this has been done for the M4 Grafyx Solution, just never mass-produced; see Mark McDougal's page at http://members.iinet.net.au/~msmcdoug/trs80/grafyx.html

Ian, Mark might still have some of the stuff to do it, and it's already designed, and he's in Australia......
 

gp2000

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... incidentally, this has been done for the M4 Grafyx Solution, just never mass-produced; see Mark McDougal's page at http://members.iinet.net.au/~msmcdoug/trs80/grafyx.html

Did Mark complete the project? Last I heard he'd built a prototype which had a number of bugs to work out but he didn't have the time to fix them. I got the impression that the bugs appeared difficult to resolve so I couldn't say if building on his work would be easy.
 

pski

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Are the Model III hi res boards so rare that a reproduction is now cost effective? I've been interested in getting one but have not yet started looking. If the originals really are impossible to find, then Ian I would be willing to buy an assembled one. I just don't have the patience to put one of those together. What to you envision the price would be roughly?
 

TRS-Ian

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@pski

Yes they are rare... of course reproduction will not be cost effective, but someone has to do it and it may as well be me... Until I assemble and test a few I can't speculate on a price, and right now I'm sussing out PCB manufacture options. A minimum run of 50 PCBs will probably be required per design.

I am looking forward to this project and hopefully people will get behind it.

Ian.
 

jltursan

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Sep 24, 2010
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Count me in for at least one Grafyx card. If I can afford a second one, I would buy another one for my 4P.

I'll get in contact with a friend and if he's also interested probably I'll go for three...
 

veco

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May 12, 2013
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95
already in progress :)

already in progress :)

Count me in for at least one Grafyx card. If I can afford a second one, I would buy another one for my 4P.

I'll get in contact with a friend and if he's also interested probably I'll go for three...

FYI, I last year, I borrowed a Grafyx card from Ian, and did the reverse-engineer. I then made a replica, the only change being using a single SRAM chip vs a decoder and several smaller srams (now hard to find). I haven't made a prototype of this yet, due to lack of time (too busy with another hobby project). I'll provide the gerber plots to Ian, so we can make these a reality. This is the first step.. if that works, I think making a similar board with SOIC components would be better (and cheaper). Another alternative would be to use a CPLD, but the 5V-tolerant chips are also hard to find, and specialized tools are required to program them. The solution here is fully TTL "as in the good old days" :)

-Fred
 

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OS9dude

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Tucson Arizona USA
Tooling up and parts inventory costs to produce these boards will be high for me in the short term, so I need to know realistically how many people are interested before proceeding.

Do people want to solder their own kits together or buy a pre-built unit?

I'd take two kits: one for the Model III and another for the Model IV


-- RP
 

veco

Experienced Member
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May 12, 2013
Messages
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I"m interested also. Can assemble it myself. Depends on the cost though.

All the components are off-the-shelf 74LSxx, so that's really cheap. A 128KB SRAM is in the $3-5 range... the connector may be the most expensive part ;) The PCB itself shouldn't be too pricey if manufactured by 50+ pieces (I'd say around $8-10).

The thing is to prototype the replica, and get it working with a modern SRAM chip. [Side note: I am doing a similar exercise with analog synthesizers, and I can't get the sram to work properly for timing reason, looks like the modern chips are too fast for some applications].

-Fred
 

gonk23

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Jun 15, 2013
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Melbourne, Australia
All the components are off-the-shelf 74LSxx, so that's really cheap. A 128KB SRAM is in the $3-5 range... the connector may be the most expensive part ;) The PCB itself shouldn't be too pricey if manufactured by 50+ pieces (I'd say around $8-10).

Of course, you're referring to the Model 4 boards. The Model III board would be much more difficult to build and install because the Model III wasn't designed to have a hi-res card like the Model 4. It requires a video chip + extra circuitry. It also came with a replacement back panel RF shield which the hi-res card mounts inside + other wires to intercept the video signal. There's also the 50-pin expansion bus adaptor cable so that the hi-res card can use the required signals and pass them on to other expansion devices (e.g. FreHD). A simple modification to the mainboard is also required.
 

jltursan

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Sep 24, 2010
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Madrid, Spain
FYI, I last year, I borrowed a Grafyx card from Ian, and did the reverse-engineer. I then made a replica, the only change being using a single SRAM chip vs a decoder and several smaller srams (now hard to find). I haven't made a prototype of this yet, due to lack of time (too busy with another hobby project). I'll provide the gerber plots to Ian, so we can make these a reality. This is the first step.. if that works, I think making a similar board with SOIC components would be better (and cheaper). Another alternative would be to use a CPLD, but the 5V-tolerant chips are also hard to find, and specialized tools are required to program them. The solution here is fully TTL "as in the good old days"

Thanks for the effort!. It's a great initiative to build a Grafyx card replica!.

I like the idea of making it fully TTL; but definitely would be great if some components can be simplified, the SRAM is a perfect example.
 
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