New member with a very sick TS1000

[ts_mike]

<whacks head with hand> Of course!! Now, I see what I did wrong! Correctly connecting the output to ground gives me 4.91V. Unfortunately, I'm pretty sure I made the same testing mistake with the original voltage regulator. If this does happen to be the "fix", I may have simply lucked into it!

Good to know that it is working. Another happy person and another retro computer saved from the scrap yard

Shhh!!! Don't jinx it!! It's too early to tell if this is a long term fix or not, but it does look promising so far (knock on wood).

If everything checks out, I'm considering getting one of these ULA heatsinks before I put the machine back together:

http://www.ebay.com/itm/Sinclair-ZX81-U ... 3cb67bd673

Since the Z80 chip is pretty much the same size, I thought about putting one on the CPU, too. The big question I have is with the clip--there doesn't seem to be one in the picture. How do I manage to clip it on? Does anyone else sell these heatsinks? I don't see any on the RWAP auction pages.

I'm going to give the Sinclair a nice long burn right now and she how she holds out... Wish me luck!

[ts_mike]

It's been another facepalm day... Had I read further in the eBay description, I would have seen that the heat sink has an adhesive backing. doh!

I've left the sinclair on for about 4 hours and it was still responding to keyboard input, so that's a good sign. After I get the heatsinks in, I'll seal her back up again and see how she does with the RAM pack et al. It is going to take a couple of weeks to get the heatsinks from the UK. I'll update this thread when they arrive to let you know if I still have any problems. Hopefully, she'll be ok and survive another 20 years, at which point I'll probably have to open her up and do a composite mod, since there will be no tube TV's around anymore to display a missing back porch signal. I hope this forum will still be around, too!

Thank you again for all your help!! I'm really grateful for all your assistance. I couldn't have done it without you! Not even close! You folks are the best!

[Paul]

If everything checks out, I'm considering getting one of these ULA heatsinks before I put the machine back together:

http://www.ebay.com/itm/Sinclair-ZX81-U ... 3cb67bd673

Since the Z80 chip is pretty much the same size, I thought about putting one on the CPU, too. The big question I have is with the clip--there doesn't seem to be one in the picture. How do I manage to clip it on? Does anyone else sell these heatsinks? I don't see any on the RWAP auction pages.

Yes you can just as well put one on your Z80. I just don't think its neccessary as a new Z80 replacement is available and cheaper than the heatsink.

As you are on your heat trip of the Zeddy: this ULA heatsink is good. But the 7805 is a source of heat that is is not neccessary! There are switching regulators that virtually do not create heat and do not need a heatsink. If you replace the 7805 with one of those recom or traco regulators (direct replacement for 7805) the heat in your zeddy will drop by a big amout (i guess around 30 degrees Celsius, but that is just a guess) and your ULA, supplied with a heatsink, will take big advantage from that.
There might be some verly little ripple on the power after you replaced your 7805 that might also lead to some distortions on the screen (well they are not visible to me, but others say they were there). If you are thinking of using a video input to a tv or monitor, the ZX81CCP is a very good solution you might build in while your zeddy is still open (and it will also take care of the minimal distortions on the screen).

[RetroTechie]

Don't bother to put a heatsink on a Z80. Nobody does that since it's simply not needed.

If you're worried about the Z80 heating up (or you want to reduce overall power consumption), better spend that GBP 3.49 on a CMOS Z80 (Z84C00nn where nn stands for MHz it's rated for). Less power consumed by IC's = double profit: less heating by IC's themselves, and less power wasted by +5V regulator to supply those IC's. With a CMOS Z80 you can't even feel it heating up (duhh... 25 mW / MHz or so, almost negligible). More for NMOS Z80's, but those also rarely die, and spares are cheap & easy to find.

[ts_mike]

Hello, again! I wanted to give you an update on my TS1000. I installed the heatsink and resoldered the "spring". Things seem to be looking good again, except that it looks like I damaged the keyboard ribbon. All the keys seem to work, except for the numbers 1-5. There is no obvious break in the ribbon, so I don't know where to look for damage. Is there a map that labels which keyboard key goes to which ribbon trace? I can maybe find a way to test and repair the trace. I'd rather not spend another $20 (and a few weeks waiting) on a new membrane if I can help it.

Once again, your advice and assistance are greatly appreciated! Thank you again!

UPDATE: If I pull out the board and "stretch" the membrane ribbon, the keys work fine. It seems only to "fail" when scrunched up in the case... So, the ribbon is working, per se, but it "breaks" temporarily when bent the proper way in the case. Pull out the board and it still works. Certainly a bad connection. Thoughts?

UPDATE2: So, I seem to have found a temporary solution. I've taped down the ribbon with electrical tape and now it bends in the "wrong" direction. That seems to be solving the problem for now, but I imagine not for long. I'm guessing the problem is at the tip of the ribbon, since I was able to get good continuity testing in most places I was testing. Hmmm.... Maybe I should get one of those new membranes just in case this "fix" fails...

[TMAOne]

A schematic is available at http://www.mainbyte.com/ts1000/good_schematic_hi.jpg You can see the line your break must be in. Note that "D1" refers to Data Line 1, not Diode 1, as the diodes are labeled left to right on the motherboard. Confusing, that.

good_schematic_hi.jpg

(993.66 KiB) Downloaded 3604 times

Option 1: Even though you said you don't want to, go ahead and buy the replacement keyboard from RWAP Software at http://www.sellmyretro.com/offer/detail ... rd%29-2292 I've bought two of them now and they're better than the originals--more flexible and durable, not as brittle. I thickened the ends with a sliver of electrical tape (on the non-conductive side obviously) to get a snug fit. I expect them to last a long time.

Option 2: If the break is near the end of the ribbon, you can cut the broken end off, trim the excess ribbon notch appropriately, and still have enough trace length to reach the terminals. If you're lucky.

Option 2B: If you're not lucky, I've heard tell of folk un-soldering the terminals from the motherboard, gluing them to the roof of the case so the ribbon will reach, and then running conventional wire back down to the mother to complete the connection. Sounds like work to me. Are you sure you don't want to spend the equivalent of £10? (I knew there was a reason I bookmarked that ascii chart.)

Option 3: I haven't tried this and don't necessarily recommend it, but there is such a thing as "wire glue". Look on eBay. It's about 5 dollars, and again you'd have to wait for it, unless you can find somewhere else it can be found. It is conductive adhesive. I've tried to use it on glass solar cells, which are near impossible to solder. Mixed success. It tends to be a pretty darned good conductor, but lousy glue. In this case you wouldn't need much "glue". if you could shore up the back of the trace break with tape to keep that part from bending too much, a tiny spot of wire glue put on with the end of a toothpick might be enough to complete the circuit. I emphasize "might".

Just thoughts, YMMV etc.
Ian

[ts_mike]

I'm happy to report that it seems like things are back up and running now (knock on wood). After installing the ULA heat sink, I put her back together and ran her hard without any problems. I got some blue-tack to stick the 16K rampack on (how come that extremely useful tip never made it to the US?), and managed to load 3-D Monster maze for a high-power test run. So far, so good!

Thank you all for all your expert help and advice! I couldn't have done it without you!

I'm having a lot of fun reliving some old memories, and making new ones. It's amazing what people managed to do with this machine! Now that I know much more about programming than I did so many years ago, I think I can maybe figure out a few tricks on my own. If I come up with something good, I'll be sure to post it here.

Once again, thank you!

[gozzo]

Woo-hoo! At least someones having success - I have 4 duff zx81's and 1 or more iffy rampacks waiting for me to sort them out - sometime !!

[TMAOne]

Congratulations ts_mike.

Ignore my earlier comment about the possibility of using wire glue to complete the circuit on a broken keyboard ribbon trace. I just tried it on a recently acquired Timex. It didn't work. There was no continuity over the break from one side of the glue spot to the other. I'm not sure why--I thought it would go. So I trimmed the ribbon up and put the cracked bit in the bin. There's still enough left to work with.

This particular Timex had another problem. The receiver that the ribbon fits into had no metal contacts inside! It didn't look like it had been tampered with; they just weren't there. I have to assume this was a factory defect and this particular unit has never worked until today, when I soldered in a good connector. (I was going to harvest one from one of the two mysteriously non-working motherboards I have, but found a suitable connector in my junk box. Okay, junk room. Well, actually its the whole house Your Honour.

Preventing the ubiquitous nemesis "RAM pack wobble" with "Stick-Tac" sounds like a great idea, if that's what that means--the stuff teachers use to hang up your kids' latest artwork? Is it called Blue-Tack now?

I use another solution. Every ZX81 or TS-1000 I own, I tin the pads of the interface on the motherboard. It gives them a tad more thickness, and a softer surface for the RAM pack contacts to bind to so they don't momentarily lose contact as easily. It seems to work very well. I also solder the power supply wires directly to the circuit board, and usually the SAVE and LOAD cables too. Those cheap %#+@& phone jacks are for the birds. Nothing spells frustration like typing in a brilliant program on that abysmal keyboard, and then having the power cord lose contact for the nanosecond it takes to erase it all. Grrr,...

Ian

[ts_mike]

Congratulations ts_mike.

Thanks! I'm glad I got lucky with this one. There are some classic systems that emulate well, like the Commodore 64. The ZX81/TS1000, however, is not one of them. Despite the EXCELLENT simulation of the EOX emulator, the Sinclair's unique keyboard and hardware quirks add an "atmosphere" that is impossible to truly emulate.

Preventing the ubiquitous nemesis "RAM pack wobble" with "Stick-Tac" sounds like a great idea, if that's what that means--the stuff teachers use to hang up your kids' latest artwork? Is it called Blue-Tack now?

Yep. It's the same stuff! I got that tip from Ol' Uncle Clive himself, or actually the actor portraying him in the BBC Micro Men movie. He mentioned the "engineering solution" in the movie to a Sinclair User reporter. Apparently, this trick was de rigueur for the British ZX-81 back then. It was even recommended on the inside of many program cassette labels. Since very little European software or periodicals ever made it to the states, the "secret" remained completely a European one. In the old days, I remember trying electrical tape with little success. I've heard that double sided foam tape also works well.

I use another solution. Every ZX81 or TS-1000 I own, I tin the pads of the interface on the motherboard. It gives them a tad more thickness, and a softer surface for the RAM pack contacts to bind to so they don't momentarily lose contact as easily. It seems to work very well. I also solder the power supply wires directly to the circuit board, and usually the SAVE and LOAD cables too. Those cheap %#+@& phone jacks are for the birds. Nothing spells frustration like typing in a brilliant program on that abysmal keyboard, and then having the power cord lose contact for the nanosecond it takes to erase it all. Grrr,...

Ian

Hmmm... that's one thing I never had a problem with... the phono jacks. Actually, I was probably one of the few people that didn't really have any problems with cassette loading or saving. I must have had a perfect tape recorder. It was an older model--made in the late 70's. I used Radio Shack tapes for the most part. They certainly were mediocre tapes for audio, but I guess they hit the sweet spot for sinclair programs.