ZX80/81 on a modern TV...

[bobs]

Is there an easy way of getting a ZX80 / ZX81 to work on a modern TV? I've previously been running my ZX80 & one of my ZX81s on an old analogue-tuned Philips B/W portable, with my second ZX81 appearing to work correctly on a modern TV (guess it has the ULA with the back-porch signal?), but lately the focus on that TV has been beginning to blur, making it increasing painful to use the computers on it.

Is it possible to get them to produce the correct signal, or an easy way of converting them to produce a composite or SCART output? Although I'd hate to make any major changes to my ZX80, I do really want to keep being able to use it.

[Chad]

I've used this circuit successfully on ZX81's to provide composite video:



There's a version of it floating about without the capacitor too, but I found adding it vastly improves the contrast. I tend to chuck out the PCB in the modulator and house it in there, using the existing TV connector as composite video. I don't think I'd want to irreversably mod a ZX80 in the same way, in which case I'm sure you could tack the few wires onto the PCB and trail a phono socket out of one of the existing case holes.

I've not tried this on a ZX80 and don't know if it would work - but I know they share very similar hardware. On ZX81's the success of this is somewhat dependent on the ULA producing a back porch, I don't know if the ZX80 suffers from this issue.

Good luck!

Chad

[Moggy]

Hi all

even simpler mod is to use a phono lead, solder the braid to modulator and inner core to to left hand wire exiting modulator (when viewed from front) does away with transistor etc used this method for a while now on zx80 as well (only way i could get my usa zx80 to work on uk tv)
I must add I have only used this method with the small modern b/w tv, 7" screen type of thing used in cars and caravans and a few old security cctv monitors that would only accept composit signal, never tried with modern colour sets maybe the circuitry is needed for that.

regards moggy

[Chad]

even simpler mod is to use a phono lead, solder the braid to modulator and inner core to to left hand wire exiting modulator

I've tried this method too, but I found the signal strength to be pretty poor, and had to crank the brightness on the TV right up to get anywhere near a white background. This may be more an issue with modern TVs though - I think older ones were a lot more tolerant of quirky signals.

By far the best results I've had are with the circuit I mentioned above. Only one of my four ZX81's doesn't work well with this which I think is down to the missing back porch. And despite what I've read, I've another ZX81 with the same version ULA which works perfectly... so perhaps it's only a batch/date range/some-other-factor which are affected?

[Moggy]

Agreed Chad
the early ulas (2C158E and 2C184E) seemed especialy dull, some with a "wavy screen" effect. Ula 2C210E which I think appeared on the issue three boards seemed much brighter.
Regards Moggy

[lov1]

Hi all,

I am new on the forum and with ZX-81 computers as well. When young (16 yrs old), always wanted to have one but they were not easy to get in Mexico, many years later, I got a TS-1000 on ebay.

Seller says it has never been used, and looks like that, but I can not see it is working as I don't know how to connect it to a tv set. it has an internal modulator for ch.2 and ch.3 but I don't know how to connect TS1000 to a TV.

Can you please advise on how to connect it and what I need?

Regards

Luis

[Spirantho]

Hi Luis,

This is a little off-topic (probably better in another thread) but you need an RF aerial cable. I'm not too hot on Mexican TV standard (you use NTSC-M I believe) but you should be able to connect the modulator directly to the TV's 75 Ohm aerial input (you might need a switchbox). Then you just tune your TV to channel 2 or 3 and you should get a picture.

It probably won't be a good picture, though, so if you know which end of a soldering iron to hold, you may be better off with the composite mods mentioned in this thread. Then you can connect it straight to the Video In of your TV and get a much better picture.

Hope that helps a little!

[yerzmyey]

Is there an easy way of getting a ZX80 / ZX81 to work on a modern TV?

A good question.
I was very suprised when I found first time about older ULA version in ZX81 and its weaker signal

As for me, I have to get myself a suitable TV set (the most simple device, black/white, probably Chinese, touristic machine, I would say, working with ZX81 perfectly).

But last times Factor6 wrote to me a very interesting info:

_______________________________
And I made a VIDEO-OUT
mod yesterday, and it works
It's connected to the internal CINCH TV OUT
connector, so there is no need to make any extra hole
to the computer. Just one resistor and one transistor is needed. The
TV OUT works then as TV OUT _AND_ VIDEO OUT simultaneoulsy. So you can
connect it to a TV ve RF lead or to a monitor via CINCH cable. No need
to switch anything.
_______________________________

I can ask him for details, if required.

Y

[lov1]

yerzmyey,

Yes, please try to get as much info as possible, in my case, I got a tv modulator but even with it, my tv sets are not displaying anything but a black screen.

Regards

Luis

[yerzmyey]

Done.

I will let You know as soon as possible.

Greetz!