jdgabbard Posted August 23, 2015 Share Posted August 23, 2015 Got this baby yesterday in the mail. Sadly, it had seen better days.... While it was in decent condition, it came with no cables or accessories. Meaning that I had to do some fabrication. First up was a power cable. I dug and dug through my parts bin until I finally found a 1.8mm mono plug that came with a universal power supply. And with a little bit of ingenuity, a DC jack, a NES power supply, and some solder I had a working power supply. Next I dug around until I found a COAX to RCA type adapter. Hooked it up to the antenna in and plugged her in. Screen went black and I had a very faint view of a prompt. Well, I guess the modulator went bad over the last 33yrs, so I went back to the bench. After several minutes of desoldering I had it removed, and was at work getting a Composite replacement soldered together. After about an hour I had it all done and complete. Next up was to test it out. I went back to the living room and plugged it in. Shazzam! My black magic worked! Sadly, the membrane keyboard has broken buttons. However, I did find a source for new production membranes, and got one ordered. (About $19 USD). Since it is already modded, I guess I might as well see about a RAM upgrade. Going to see if I can find any plans for an internal mod. However, I seem to only see links for the ZX-81, which has a slightly different schematic. Might be able to work it out. (Feel free to post a link if you have one...) But when the keyboard comes in and I get it installed this baby will be ready to run like new. 5 Quote Link to comment Share on other sites More sharing options...
Keatah Posted August 23, 2015 Share Posted August 23, 2015 Bonus points if you put Skylake in there! Quote Link to comment Share on other sites More sharing options...
ClausB Posted August 23, 2015 Share Posted August 23, 2015 Congrats! Got a link to the composite video mod? I added 16K SRAM in the day. Nowadays you can do it with a single chip. http://atariage.com/forums/gallery/image/12227-zx81/ Quote Link to comment Share on other sites More sharing options...
ClausB Posted August 23, 2015 Share Posted August 23, 2015 Did you try trimming the worn end of the keyboard cable? Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted August 23, 2015 Share Posted August 23, 2015 However, I did find a source for new production membranes, and got one ordered. (About $19 USD). Now THAT is very interesting. What is the company/source? Some people might be interested in seeing if the company has any or could make any for the TI-99/4A Mitsumi (crap keyboard). A lot of this old tech is starting to fail, go out of spec or just plain die altogether. Having lists of sources for replacement parts will be invaluable resource for keeping these old units out of peoples trash cans. Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted August 23, 2015 Author Share Posted August 23, 2015 Here is the link for the replacement membrane. It's in the UK. But they didn't say they wouldn't ship to the States. The Timex is just a modified zx-81, so it should work. http://www.rwapsoftware.co.uk/zx812.html As for the video mod, the link is below. Again, it's for the ZX-81. And they have a difference in modulators. After using my logic analyzer and scope on the circuit, it appears that the modulator might have been ok. But the circuit going from the CPU logic chip to the modulator was showing as a solid high signal. So I got my feed from the CPU logic chip pin instead of from the back end of the circuit. Requires a little more wire, but it is neat considering I just ran the wires through the original solder holes. VCC and GND were both pulled from the solder points of the voltage regulator. So if anyone repeats this mod, that would be what I would do again. Also I used 30awg wire wrap wire, since it was small enough to fit through the solder pad holes. http://www.zx81.de/english/_frame_e.htm After I had prototyped this circuit, it only seemed logical to use what was already there to make it look original. Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted August 23, 2015 Author Share Posted August 23, 2015 And as far as the TI-99, it doesn't use a membrane. It has soldered in buttons... I have a parts TI that I and going to use the keyboard for input on a Z80 computer I'm building... It's not real far along, but I'm making progress none the less... Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted August 23, 2015 Author Share Posted August 23, 2015 Bonus points if you put Skylake in there! Not familiar with it. Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted August 23, 2015 Author Share Posted August 23, 2015 Did you try trimming the worn end of the keyboard cable? Yeah, that was my first idea. But after doing so still didn't work. I then noticed that some buttons were completely depressed. While the ones that worked were still bubbled up. My guess is they keyboard broke on the buttons themselves. Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted August 23, 2015 Share Posted August 23, 2015 And as far as the TI-99, it doesn't use a membrane. It has soldered in buttons... I have a parts TI that I and going to use the keyboard for input on a Z80 computer I'm building... It's not real far along, but I'm making progress none the less... image.jpg Actually the TI had multiple style keyboards by different manufactures over the period it was on the active market. For most of the units, there was the mechanical type you mention, towards the end when they switched to the BEIGE QI units to save money, they started putting in Mitsumi membrane keyboards like this one: The failure rate on the above style keyboard is astronomical. The type pictured below is the preferred type to own. 1 Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted August 23, 2015 Share Posted August 23, 2015 One guy even put a TS1000/ZX81 in a TI case! Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted August 23, 2015 Author Share Posted August 23, 2015 I was aware of the tan models, but wasn't aware of difference in keyboards. Interesting. As for the ZX-99... How did he do the keyboard? With only 8 data lines, and 5 lines which are written high, there are only 13 total pins on the Zx. While there are 15 on the TI. And Wgile I could go look, I'm pretty certain they don't match up to the TI's matrix. Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted August 23, 2015 Author Share Posted August 23, 2015 Of course I suppose you could always use a MCU to decode it and write to the keyboard pins... Quote Link to comment Share on other sites More sharing options...
jd_1138 Posted August 26, 2015 Share Posted August 26, 2015 I had one of those in '85. The keyboard was pretty miserable. Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted September 1, 2015 Author Share Posted September 1, 2015 For anyone interested in the replacement keyboards for the ZX81 or TS-1000, here are some pictures of the piece that I receieved in the mail. I'll post a review when I get it installed. 2 Quote Link to comment Share on other sites More sharing options...
Compumater Posted September 1, 2015 Share Posted September 1, 2015 If you want your Timex 1000 to be truly useful and down right fun to play with, skip trying to use 30+ year old tapes and spend the $$ on the incredible ZXPAND. I've always been a fan of the ZX-81 /TS-1000 computers, but when I spent the money on a ZXPANDER It was like I new system. Its basicly a 32K ram pack, and a SD card reader that allows you to hold every program ever made for them on one small chip. (Think hard drive) its also menu driven! Then it goes a step farther and with another add on It adds a joystick/mouse plug and sound! I love mine, and have used my TS 1000 more since I got it then in the 20 years before it. I'm a Zx freak, I've modded mine to have reverse video and have it hooked to the little 9 inch apple 2C monitor. I also hand built a nice full keyboard. Its increadable to be able to swap in game after game with out having to try and load them over and over from my tape deck, or trying to convert them to .wavs to pipe them in from my IBM. Search for ZXpand and check it out. 2 Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted September 1, 2015 Author Share Posted September 1, 2015 Yeah, I saw the ZXpand cards. I'm not really that into the ZX. I am more of a 'collector'. I like vintage tech, and want to see it kept alive. Some things I keep going, and buy tee addong for. Like the TI. But I'm more like the guy that says 'Wait till you see this!' And pulls some cool vintage device out of a closet or from a shelf. Sure, I tot on them some. But the only one I REALLY play with besides my 90s build computer is my TI-99. I have three of them. One working model at the house, one parts machine. And one in near mint that in long term loan to a friend and fellow retro-tech enthusiast. Quote Link to comment Share on other sites More sharing options...
MarkO Posted September 2, 2015 Share Posted September 2, 2015 << SNIP >> I'm a Zx freak, I've modded mine to have reverse video and have it hooked to the little 9 inch apple 2C monitor. I also hand built a nice full keyboard. Its increadable to be able to swap in game after game with out having to try and load them over and over from my tape deck, or trying to convert them to .wavs to pipe them in from my IBM. Search for ZXpand and check it out. Do you have any Web Sites for Mods like the Reverse Video?? I have a collection of ZX81/TS1000s, the ZX81 being the first computer I owned, I would like to modyfy some of them.. MarkO Quote Link to comment Share on other sites More sharing options...
Compumater Posted September 3, 2015 Share Posted September 3, 2015 Do you have any Web Sites for Mods like the Reverse Video?? I have a collection of ZX81/TS1000s, the ZX81 being the first computer I owned, I would like to modyfy some of them.. MarkO Yes Check out RWAP on google. It will lead you to the site that sells keyboard replacements and the ZXPand. from there the guy runs a E-bay type site called Sell my retro. On that site, I found a guy that makes a small board that replaces the old RF modulator with a nice clean Video out circuit. it has a jumper on it to reverse the video. I cannot understate how nice and "Professional" looking the ZX looks on a black screen with white letters, or even better a black screen with green letters. I don't think I paid more then $10 for it plus shipping. I bought a few of them so I could modify several of the units that I have. Its like 3 wires you solder on and your done. I would post a direct link, but the site seems to be down at the moment. 1 Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted September 3, 2015 Author Share Posted September 3, 2015 Somebody didn't read the thread before posting, lol... Thanks for pointing him in the right direction, Computermater. Yeah, I thought about doing a B/W reverse video mod. But I got lazy and just went for the single transistor/resistor composite mod. It's easy, and it works great. Though, I may go back and change it eventually. By my calculations there is ample room for both mods in the modulator box. And since the modulator switch on the bottom is no longer used, there is an easy way to get either signal on the fly. Probably have to cut a few traces. But that isn't anything that a sharp knife or dremel can't fix. 2 Quote Link to comment Share on other sites More sharing options...
MarkO Posted September 4, 2015 Share Posted September 4, 2015 Sorry.. I have been to the RWAP site before, but didn't see the links to other Sinclair related sites... MarkO Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted September 4, 2015 Author Share Posted September 4, 2015 Mark, if you go to the link i provided above, and scroll down, there is a table. The first item in it is the keyboard with a link. Hope it helps. As for fit and function, I can report that it fits awesome. And works better than expected. The key sensitivity are just right for this type of keyboard. 1 Quote Link to comment Share on other sites More sharing options...
Seob Posted September 12, 2015 Share Posted September 12, 2015 I also added a composite mod to my zx81, and had to cut down the keyboard ribbon since it was broken. The unit is working fine now. But my 16k expansion is broken. Would like to get a working on, since 1k is just to little memory. Don't want to go the zxpand way. 1 Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted September 15, 2015 Author Share Posted September 15, 2015 http://www.zx81.de/english/32k-rame.htm The link above is to a 32k internal SRAM mod. I can verify it works well (I made a change to the schematic, and used two transistors and a resistor to for an AND gate rather than use the two gates of a 74HCT00). The only problem I've had is with the battery backup. To appears that the 3v 2032 I used doesn't have enough voltage to hold he charges in the particular 62256 SRAM that I used. I'll have to check the datasheet, as a 3.6v might not do either... I did this mod on a second TS1000 I acquired that was in horrible shape (broken case, destroyed jeyboard, faulty modulator, etc...). I used a ABS compound to repair the PCB risers, did a composite mod, altered the heatsink, etched a tactile keyboard, installed a CMOS z80, and a few other things. Overall, I'm happy with it. But need to design a keyboard overlay for it. There wasn't enough room for a single sided keyboard PCB that matched the exact layout of the ZX. But it's in the same pattern. Here are some pics. But really, the internal SRAM mod is legit. 1 Quote Link to comment Share on other sites More sharing options...
jdgabbard Posted September 15, 2015 Author Share Posted September 15, 2015 Mark, I tried replying to you over on the tube...but not sure if it went through... Either way, I updated it. 1 Quote Link to comment Share on other sites More sharing options...
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