Sinclair ZX80 / ZX81 / Z88 Forums

I have just finished refurbing a toastrack and the jail bars were a bit noticeable so I did the jail bar mod as shown here https://spectrumforeveryone.com/technic ... -spectrum/

It has certainly mostly got rid of the jail-bars visible on the white background when it boots up but in some games there is a very noticeable level of jail barring going on.


Note the vertical ‘stripe’:

Even worse on the main menu:

Up close on a CRT TV:

They almost look like character boundaries?

Is there anything I can do further to reduce this? It was like it from the outset and isn’t as bad as it was to start with.

I have fully recapped it and replaced the voltage regulator.

Any help appreciated thanks!

Yeah, desolder C1 to C8 (including those shiny new capacitors if you used a value of less than 470nF) and fit 470nF or 1µF types instead

Note that try to keep the leads as short as possible.

Also consider doing the same with C30 and C75.

Although some of the artefacts may be due to a problem with the ULA.

Mark

1024MAK wrote: ↑Thu Nov 19, 2020 1:43 am Yeah, desolder C1 to C8 (including those shiny new capacitors if you used a value of less than 470nF) and fit 470nF or 1uF types instead

Note that try to keep the leads as short as possible.

Also consider doing the same with C30 and C75.

Although some of the artefacts may be due to a problem with the ULA.

Mark

Thanks Mark

C7 and 8 were replaced with 1uF types. Will do the rest!

Once I’ve ordered some more. Only 2 left. Typical.

1uF multi layer ceramics?

Lardo Boffin wrote: ↑Thu Nov 19, 2020 8:42 am 1uF multi-layer ceramics?

Yes!

Mark

1024MAK wrote: ↑Thu Nov 19, 2020 11:23 am

Lardo Boffin wrote: ↑Thu Nov 19, 2020 8:42 am 1uF multi-layer ceramics?

Yes!

Mark

Thanks. Wasn’t sure about C30 and C75.

Lardo Boffin wrote: ↑Thu Nov 19, 2020 12:03 pm

1024MAK wrote: ↑Thu Nov 19, 2020 11:23 am

Lardo Boffin wrote: ↑Thu Nov 19, 2020 8:42 am 1uF multi-layer ceramics?

Yes!

Mark

Thanks. Wasn’t sure about C30 and C75.

Use 1µF for these as well.

Mark

I have replaced all the caps but it made no difference. Dodgy ULA?

Maybe time to get a vLA128?

In the short term it turns out I can use my SpectraSCART with the toastrack and it produces a perfect picture.
It only produces beeper noises directly though so it looks like I need to enter the world of butchering modifying cables.

Thanks to (a lot of) assistance from Paul Farrow one cable delicately bodged modified and I have a great picture and full sound!


Wish I had found a longer cable for the MIC socket. Ah well, cable take 2 I guess.