ZX81 Versions/Issues

[PokeMon]

Anyway if it is working with a TV - you wouldn't have the best signal via the modulator.
It is like in the 80's but when you compare to the display you know from your smart phone or your hd television there is a big difference.
I would prefer a video mod rather than swapping the ULAs - both video mods ZXvid and ZX8-CCB add the missing backporch to your ULA and provide a clear and crispy composite video signal which nearly any TV accepts (even the newest LCD). There is no lack about the older ULA's except the missing backporch resulting in a dark picture on the TV. But you should maybe do a test if there comes a signal out with an old TV - this can be any old TV from a friend or better your grandma.

[RetroTechie]

Welcome here, nzbevan!

If you're going to order a replacement 2C210E version ULA or video improvement circuit, I suggest you order a new keyboard membrane while you're at it (well perhaps after checking that a new membrane isn't already fitted!).

Why? Because most likely that membrane has turned to crap after ~30 years. If it still works, chances are it won't after you've opened the case. Ordering a replacement together with ULA or video circuit will save on the shipping costs.

If you go for a replacement ULA, make sure to get a heatsink on it! That'll greatly lengthen whatever life is left in that part. Also the composite video mod is highly recommended in that case.

So either I need to go back really far to a VERY old TV (I'm guessing that means an old B&W CRT one) or upgrade my ULA chip which, it appears, may let me use any TV with a UHF tuner and Coaxial socket.

The one thing going for old B&W CRT is that they virtually come for free these days. So if you have the space for it, and can find one in your area, then yes it's a valid option. The new ULA or video circuit has the advantage that it's easier to connect your ZX81 to any TV you come across.

Either way, assume that a fix will mean "turn RF output into composite video". No VHF/UHF channel searching, modulator not needed anymore, better picture quality. The only reason I can think of to use a ZX81 with original RF output, is if you've only got a TV that has RF input and nothing else. Should be a non-issue these days...

[Rishi]

Either way, assume that a fix will mean "turn RF output into composite video". No VHF/UHF channel searching, modulator not needed anymore, better picture quality. The only reason I can think of to use a ZX81 with original RF output, is if you've only got a TV that has RF input and nothing else. Should be a non-issue these days...

I'm planning to do the Mod as well, Schematic is very simple, just looking at the Transistor, would a BC547 do ? and i can leave the RF Genarator where it is can't i ?

[1024MAK]

Yes, any good NPN small signal transistor should work okay.

You can either leave the modulator alone and add an extra phono/RCA/clinch socket or lead with an in-line socket.

Or, the recommended option is to disconnect the +5V supply wire and the video input wire to the modulator. Next, inside disconnect the centre terminal of the phono/RCA/clinch socket from the internal circuitry (components). Then wire the composite video transistor circuit in. With the input being routed via one of the existing wire holes from the ZX81 board. Do the same for the new +5V supply wire. Use the case of the modulator for the 0V/ground. Then wire the output to the centre terminal of the phono/RCA/clinch socket.

Mark

[nzbevan]

Thanks so much folks!

I've decided to get a ZXvid, and at the same time a new keyboard membrane. I'm sending my machine off to Sell My Retro to do it, as the price to get them to do the job for me is much the same as buying a soldering iron. Once it comes back I'll probably get a second hand smallish LCD TV to go with it - just the right size to sit on a desk. Then I'll just need that data-corder! (Who apart from us uses tape players at all now, let alone with both a mic and earphone socket?)
I can't even find one on UK eBay now! Anyone know where to find one? There must be some floating around...

[Moggy]

Argos item No..909/1821.
£35 at which point most people throw a wobbly but it's hopefully a one off purchase for your hobby, and no dearer than a good Saturday night out at which a lot of folk would happily throw a weeks wages at without complaint.

Also it comes with a guarantee unlike ebay tat, buy cheap buy twice as they say.

Or this one by Sony which is the popular one for zeddy use but not at the ridiculous price quoted here.

http://www.amazon.co.uk/Sony-TCM939-Sho ... B002H9HZH8

The perfect solution is the ZXpand SD card and 32k memory device. a large rampack and storage all in one from sell my retro. (that's if Charlie has made any recently.)

EDIT.
Looks like none in stock at this time.

[Rishi]

I made a cable that goes into my laptop, one end 2x mono 3.5mm other side 3.5mm TRRS where TR is connected to EAR , R=GND and sleeve via a 1K resistor (or the input is not recognized because the ZX81 only has a 1K across where i needed at least 1.5K) to MIC. and i did the increased output Mod. Recording with Audicity and playing back (Wav only, but these days space in my hard drive is loadz ) Tapeutils was a bit funky for me but ZXC & ZXD works for me (haven't tested ZXD tbh) although they are 16 Bit which means they can only run on a 64 bit OS using DosBox which slows things down a bit. but on my old 32 bit windows it runs fast ! and Audicty imports the RAW (just need to set the sample rate to 22500 and if you do resample although there is no need, make sure to turn dither off) Off course the SD-card is in some way the way to go.

[NicholsMark]

Actually i also uses the zx81's plus 3 TS1000's and it has the same issue as you.
Some times it has green resist some times red, and also some will have 5 chips some will have 4.
But can't remember which variations seem to go with each other maybe anything is possible. Have never yet seen an issue you mentioned here thet does it exist?
Only thing I do know is that the earlier ULA 2C184E is a problem.