1. Not old. Vintage. :)

Researching the TRS-80 Coco 1/2/3 repairs & upgrades and differences between them.

Discussion in 'SIG: 8-Bit Hardware' started by M.D.Baker, Sep 18, 2021.

  1. by Andy Barr
    Andy Barr

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    Again, it's riveting stuff this as I had no idea what form, shape or design the Tandy Co Co's went for in terms of expansion and peripheral boxes.

    They are quite something to behold in their variation and, at times, bulk.

    All I recall were the basic Tandy colour micros on the shelf or in the window of the same name store and me thinking... what strange beasts are these and then someone saying "They're a bit like a Dragon" but I knew next to nothing as they were rarely (if ever) covered in the mainstream UK computer mags - would you agree, guys?

    I got the impression that anything you wanted for them would be, like the Atari, quite expensive and very much proprietary so kinda steered well away and never ever knew anyone who owned one so they remained... exotic beasts.

    You are opening up new frontiers to many of us on here, Matt - thank you.

    The specs, whilst not being amazing, are nevertheless interesting as I did not have a scooby do.
     
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  2. by M.D.Baker
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    You are welcome. By the same token they were always strange beasts to me too, just like the Coleco Adam too. I saw commercials for the Adam back in the day, the TV stations were flooded with commercials for it after it was discontinued and they were liquidating, but of course the commercials made them a going concern and seem like they were popular and well supported. But at the time I wanted nothing to do with turbo tape drives, I wanted a disk drive, and I couldn't afford even the fire sale pricing because they only sold it as a system including the printer, and had too, since the PSU for everything was in the printer! So luckily I avoided a dead system, riddled with bugs and failures, with a VERY limited software library of it's own, and then the Colecovision's game library as they were compatible, but even the Colecovision has less than a 100 titles, similar to the 7800, Lynx and Jaguar libaries because of the video game crash of '83/84. So it remained mainly a strange beast and curiosity to me, but I want one now for that very reason.

    I remember the TV stations being flooded with commercial with and without William Shatner too, for the VIC-20 not long after the C64 came out, and they were unloading overstock and like Coleco and the Adam, were acting as if it was the latest-greatest that would have software and support for years to come!

    This was also true of the TRS-80 Coco's. Though I would rather have the Coco 3, but they sell for $500 like the 1200XL. In the Coco's case though, I was an avid Radio Shack shopper as a youngster, so I remember always seeing some model of the TRS-80 Coco on display, and it did catch my attention because it was being demonstrated to someone at the time and it had the mouse and GOS environment, and pretty much looked like an Atari ST or Amiga quality computer on the surface. But even though they were meant to be low-end models, they were still selling them for $100-200 more than The C64 or Atari XL/XE's. So I tended to ignore them and only the Coco 3 caught my eye when it was released, but by then I had made my choice with the 130XE and was building a system and library for it.

    So the Coco's remained a strange beast and mystery to me as well. I never knew anyone who owned it or the ADAM. I didn't even know anyone who owned an Atari. my friends all had C64's or Vic-20's or Apple II's and one had an IBM PCjr! So again it was another 8-bit micro that I always wondered about, but was satisfied with my 130XE, and actually felt it far superior to most other 8-bits and was proud of the fact even if friends scoffed. They stopped scoffing when they saw the Atari in action, and soon wanted to play it all the time.

    Of course as many of you know, I had been planning on a C64, and if time and space and money allowed, followed with an ADAM, or BBC micro, or TRS-80 Coco, and fate or destiny just seemed to step in and put Coco stuff in my lap. Honestly I'd still rather have a C64, but they are just to damned expensive anymore, even though there are 100 on sale on eBay at any given time! Just a couple years ago you could get one for sometimes less than $50! Of course this is true of many vintages systems today.

    The Coco's don't have a huge software library either, it seems like just a couple hundred commercial/semi-commercial programs were published for it, and about a quarter to one third are 16K cartridges from Tandy itself. But, I have discovered that it, and the Dragon 32/64 can be modded to use the other's software, or at least hacked versions of the software. And I have to start looking into Dragon Software, as I might just decide it got better software released for it, maybe even more? I might just turn this puppy into a Dragon full-time. I might not have too though, it may be a plug-in module. I have to look into it more. In which case I can have the best of both worlds and 2 systems in one! And now that @Vyper68 is getting a dragon, we can compare notes maybe in this area and help each other out.
     
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  3. by Andy Barr
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    All very stimulating and illuminating, Matt, as my knowledge of systems such as the Colecovision/Adam and Coco is virtually nil so all these extra bits of flesh you keep adding to the bones is really interesting and yes of course you and Richie will be able to bridge your know how and growing expertise as you investigate potential software successes and perhaps even get your coco breathing fire...yet!

    Exciting times, fellas.

    Never better to be in to retro micro!
     
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  4. by Vyper68
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    It will be good to compare notes on your CoCo with my Dragon. I don’t have a massive amount of software currently but some of the Dragon’s library is very good. The Battlezone clone ( Rommels Revenge ) is excellent and that is Tandy compatible. Design Design also released a game called Dark Star which is also very good. There are a couple of games called BackTrack and Eddie Steady Go! which are good and may be worth checking out.
    As far as hardware goes I have built a cartridge port extender which allows a cartridge to be fitted internally while still allowing access to the cartridge port from outside. Handy if you have a 32KB RAM cartridge and want to use a disk drive. Talking of disk drives I have built myself a disk drive interface and have been using it with my Gotek drive this week, so it makes it easy to save programs as opposed tape. I have a CasDUINO that enables me to load .cas files from MSX and Dragon’s so I have access to the Dragon cassette library as the Dragon Archives have nearly all the tape software released.
    Finally I picked up a cartridge for the Dragon called DeMON which is a machine code Monitor program which worked fine. I opened the case and popped out the 4K ROM and fitted an 8K EPROM will Dragon Data’s AllDream assembler/debug software. I am waiting on another 8K EPROM and that will enable me to burn the DaSM/DeMON combo. So I will have saved myself a fair amount of money compared to buying DaSM/DeMON on feeBay.
    Last thing is now I have the replacement power board fitted I am overhauling my original Issue 4 power PCB replacing the capacitors and voltage regulators with modern replacements. So hopefully when finished it will be more stable and reliable.
     
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  5. by M.D.Baker
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    I haven't even loaded a program to my Coco 2 yet, though I have a cassette player for it and have recorded a couple of .wav files. In the spurts of free time that I've had over the past couple of months, I've only been doing upgrades to my Coco 2, and my 7800, and my 800, sort of rotating between them. Currently I'm in the middle of an S-video and audio out mod on my Coco 2 and one for my 7800 as well.

    The Coco 2 mod I am going by somebody else's schematics and on the 7800 it's a combination of a couple different mods schematics by others and some of my own design where I felt I could improve over other's. And of course the 800, while mostly done mod and upgrade-wise, is undergoing the face-lift and make-over. A the moment I actually don't have any of my 8-bit systems up and running, all are in need of repair and/or in the middle of upgrades. Of course winter is approaching fast and I should have much more free time to see these projects and several other finished finally.

    Though I mentioned them above in posts, here is what I've done to my TRS-80 Coco 2 thus far in list form:

    -upgraded internal ram from 16 to 64K.
    -upgraded OS with adapter board for larger pin eprom and added MS extended Basic
    -upgraded Motorola HMOS 6809 MPU to newer, compatible Hitachi CMOS 63x09E MPU used in Coco 3's with the 1.78Mhz turbo mode and extended features.
    -replaced all 74LS series IC's with newer 74HC or 74F series
    -removed old RF box/board and am upgrading video with replacement video board
    -upgraded the MC6847 VDG to the newer MC6847TI with lower case characters and true descenders.

    I want to get the MOOH board as it has all the other upgrades I want to do included on it, but I may have to settle for the SDC board and do the 512K ram and OS-9 upgrades myself. I want to buy an original multi-pack device to plug in several modules at once, but I may have to build my own board and case for that as well as originals are expensive and rare and only a 2-port multi-pak is still available from home-brew dealers and I want at least a 4-port if not 6-port.

    Once the video board upgrade is finished I will start investigating the TRS-80 tape and cartridge software library as well as the Dragon's and look more into what needs to be done for Dragon/Coco cross-compatibility.

    Here is a link to hardware upgrades that are compatible with both Coco's and Dragon's.

    https://thezippsterzone.com/hardware/
     
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  6. by Vyper68
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    Have you looked at the CoCo VGA @M.D.Baker ? I have put my name down on the waiting list for one as they fit Dragons as well.
    There is a PAL CoCo2 on eBay right now that I’m watching which hopefully I will be able to pick up for a reasonable price, as well as bidding on a very sorry looking Dragon 32 so I’m full on 6809 right now :) The CoCo is a 16KB model but there is no indication if it has been updated to 64K. So it will be interesting to see if I get it. The Dragon is a really sorry looking loft find so it might be a good candidate for the D.I.Y 64KB upgrade if I’m successful. I know Dave expressed an interest in getting a Dragon, it might need a new power board so it can use a standard 12V PSU.
     
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  7. by M.D.Baker
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    Yes, I'm aware of the VGA board. I decided against it myself because I think I will be perfectly satisfied with the quality of video outs I make along with the external video-to-VGA adapter/upscaler that I already have and use for all my video/S-video equipment, and in fact, I suspect works better as it does with other similar devices I've tried and would rather use an external font/character board where the VGA board rests.

    External font/character board:

    20150303_082444-1.jpg


    And that VGA board is ultimately no different than my external VGA adapter (except maybe works with color artifacting) but my external adapter has more advanced features for a better picture:
    http://www.ambery.com/dvh4.html
     
    Last edited: Nov 4, 2021
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  8. by Vyper68
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    Well if I go ahead and get one for my little Welsh wonder Matt, we can compare and discuss :)

    By the way I heard from Tormod about the 32KB upgrade and uDrive a couple of days ago so he is still active. Have you heard anything from him?

    Loosing the bid on the Dragon so going all in on the CoCo2 now.
     
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  9. by M.D.Baker
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    I just checked my emails again and no, no response from him yet. I sent one about a month and a half ago and another about a week ago.

    Good luck on the Coco. Mine was only 16K without extended basic rom, I had dram on hand to do the 64K upgrade and I needed a 28-pin adapter board I got from the Zipster site which came with the extended basic rom, so I didn't have to burn one.
     
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  10. by M.D.Baker
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    @Vyper68 , now correct me if I am wrong, but you bought a Dragon 32 and so with the 32K board you'll have 64K like the Dragon 64?
     
  11. by Vyper68
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    It would give me 32KB of extra RAM accessible via Machine Code. The Dragon 64 has a slightly different ROM and an extra interface. So not a proper D64 but it would run OS9
     
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  12. by Vyper68
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    I missed out on the Tandy CoCo2 ( it went for £122 ) so I picked up another Dragon 32 for £50 instead. It has an earlier serial number than the one I currently have, so I am hoping that (a) it works as it's the old untested chestnut but in this case I can see it's likely to be true as there is no PSU with it and (b) it is one of the earlier boards with the 8 half faulty 64K chips which you can swap with working 64K chips. That would be preferable that cutting and bypassing tracks on my current Dragon. Then I'll start saving for the CoCo VGA board.
     
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