Sinclair ZX80 / ZX81 / Z88 Forums

I concur. This idiot installed composite video mod without any problem save for adjustment of pots.

I was trying to make a composite video buffer off PIN 16 and the +5v pin of the RF box. with the transistor and resistor. I'm buying a 2600 premade board which has been proven to work on the TS-1000

Papa_Bear wrote: ↑Fri May 19, 2017 2:43 am I was trying to make a composite video buffer off PIN 16 and the +5v pin of the RF box. with the transistor and resistor.

Pin 16 of What??? I have not done this MOD on a ZX81 before.

The ZX Spectrum 48k Composite MOD just Requires a 10-16V 100uF Capacitor on the +5V Rail of RF Modulator and to Center Pin of RF Out Jack. (Once all the Original RF Circuitry has been Removed)

I have also experimented with this Same MOD on the ZX81, and it Does Work, but Picture is Darker. Will play with this and Up-Date if / when successful.

Darren in OZ

Please don't try a video out on the ZX81 without at least a transistor. Preferably use Pokemons ccp pcb. It gives a crystal clear picture.
Pin 16 of the ULA is video out.
But the ULA is VERY sensitive. Any static voltage or any low resistance (like 75 ohm) can kill the ULA.
Maybe your monitor didn't have the obligatory 75 ohm resistance. Then you were very lucky. But the next monitor you try can have this and your ULA will die.
On the spectrum video out doesn't come from the ULA directly but from a chip that mixes RGB to composite which is more robust.
Kind regards Paul

There was a transistor involved and was grounded. Like I've said this isn't going to be perfect.


Can the TS-1000 turn on without a keyboard?

Yes no problem no keyboard needed.
Also no Message "keyboard not present. Press F1 to continue"

Papa_Bear wrote: ↑Fri May 19, 2017 6:16 am There was a transistor involved and was grounded.

My comment on the ULA being very sensitive was aimed at Darren and any reader because his dangerous experiment.

anyone have a spare TS1000 for sale in case I totally screw mine up?


What are some other peripherals for the ZX81 and TS1000. I saw a little printer going for a ridiculous amount on ebay.

well... okay then


It doesnt seem to work properly

I'm following this mod using the same board

http://blog.tynemouthsoftware.co.uk/201 ... o-mod.html

I get an incredibly broken picture on my modern tv and no image on any of the crts I've tried

Wait a minute. apparently there was a coil connecting to ground... I have video now! woo on the B&W CRT as well as my modern flat screen