Sinclair ZX80 / ZX81 / Z88 Forums

I’ve made my own composite circuit, based on a transistor, a capacitor, 2 resistors and 2 diodes. Works perfectly on my Timex Sinclair 1000. Would you share the schematic? What kind of monitor are you connecting the 1000 to (which seems to me has as much to do with the quality of the resulting disp...

Cool. How did you make it? CNC? Are the vents routed out? Is that logo burned in?

Lardo Boffin wrote: ↑Thu Oct 07, 2021 12:21 am A vla81 is a modern ULA replacement (https://vdrivezx.com/vla81/).

Aside from being new and potentially more reliable a new Z80 may well be more power efficient.

For the new ones does it matter what the speed is? Will they all work?

soulmanpt wrote: ↑Wed Oct 06, 2021 6:37 pm Hi!


So far I have done a composite mod I saw on ByteDelight, added a vL81 and swapped for a new z80 from digikey.

Any advice?

What is a vL81? Also, what is the advantages of a new Z80?

1024MAK wrote: ↑Wed Oct 06, 2021 8:23 pm Shielded or braided screened co-ax cables are available with RCA / phono connectors. Although it’s not possible to tell on most pre-made cables with moulded connectors.

Look for cables specifically described as high quality video cables.

Mark

Will do, thanks

The 210E version of the ZX81 ULA is pretty compliant with the standards. Is this a UK/PAL ZX81 or a US NTSC unit? Maybe part of the issue on some of the TVs/monitors is a PAL 50hz vertical refresh rate. US NTSC The wavy pattern may be due to interference from the computer. Make sure you are using a...

Lardo Boffin wrote: ↑Wed Oct 06, 2021 11:04 am

Dukes909 wrote: ↑Wed Oct 06, 2021 3:52 am
Does anyone know if the TFW8B Atari 2600 mod works well on the Sinclairs?

Dukester

I have tried this a couple of times and it worked ok on one TV but not very well on the other three I tried.

Ok thatnks for that info.
Dukester

Does anyone know if the TFW8B Atari 2600 mod works well on the Sinclairs? . You appear to have been unlucky in that you have two TVs that are not happy and won’t work. Unfortunately it’s the luck of the draw on what works and what does not. Mark Well, fiddle faddle. Thanks again for the extra detai...

An update: I added one 1N4148 and then 2 in series. First tried this with the 1000 connected to a JVC LCD TV/monitor. Made no difference in stability of the image. Then tried a 100Ω resistor between the RCA (signal) pin and 0V/GND...no dice there either. I then tried connecting with the single diode...

Lack of stability indicates that the TV is not happy with the sync part of the signal. You could try adding one or two silicon signal diodes (such as 1N4148 or1N914) between the input from the ULA and resistor R1. The anode (a) end goes towards the ULA. The cathode (k) goes towards resistor R1. If ...