Sinclair ZX80 / ZX81 / Z88 Forums

I got my kit today and built it up.

It works great functionally, but it causes bad interference in my monitor (squiggly lines). I have a 210e ULA and a simple transistor mod. The video is clean with nothing plugged in, and also the Timex 16k packs. It only seems to get interference from ZXBlast.

Is there anything I can do? Some kind of filtering on the line(s) to the expansion port?

Is this just on the ZXblast main/config screen or even when you start a ZX81 instance (by pressing "1" for example) ?
What kind of monitor do you use ?
LCD or CRT ?

It's on every screen as long as ZXblast is plugged in... title, menu, and instances.

I have two CRT displays- a Sony PVM and a 20" television. It's better on the television than the Sony, but still wavy.

I'm going to see if I can find a ferrite bead and put it on the video out wire and see if it helps.

Could it be a bad power supply some of the older Sinclair power supplies have been known to have smoothing capacitors that are as dry as a bone and therefore very ineffective, any additional loading zxpand , rampack, ext causes the wavy lines

Just a thought

Regards andy

Maybe you could check the power supply.
Did you already plug a USB stick in ? Is there a difference if USB plugged in or not ?
Some USB media flash disk draw quite amount of power.

Did you buy the complete module or an assembly kit ? I actually don't know.

Thanks, I tried 4 different 9V adapters, same thing. USB stick in or out doesn't affect it.

Yes, I bought kit and built it. I'm sure it's something funny with my composite mod or something. I will try some ferrite cores tonight and hopefully that will clear it up. Otherwise, maybe some cap(s) to filter whatever is getting into the video signal.

Well darn- Ferrite core did nothing at all. Somehow interference still leaking in from somewhere.

I solved it. Adding a 10uf electolytic capacitor between 5v and ground on my transistor video amp solved it completely.
Output is crystal clear!

Enjoying the ZXBlast- great project.
It would be nice to have a file manager, though.

I did figure out how to load at least one two-part game.
HRCHESS
1) Change block 2 to RAM (can you save this permanently?)
2) Shift-shift-L hrchess.p
3) It tries to load second part from tape. press space to exit.
4) Change back to slow mode (shift-d) (ZXblast menu won't appear when in fast mode)
5) Shift-shift-L chess.p
Now it runs!

Glad you made it !
I am working at the file manager from today on as I was quite busy last two weeks in my work.

There is no load batch sequence but if you have different steps and complex setup you can save a complete instance while entering a filename with extension .BAK (stores complete memory) and you can even save a game or program during running mode, to save a game at a specific level and continue later. The program will be continued automatically when loaded again with .BAK extension.

The same is done with all instances (for 512k version) when using BACKUP over the tools menu in instance 0. This is a one key system startup and restores all running instances when pressing "L" at the start screen (as "any key"). This may take about 2 seconds per active instance while having a white screen - so be patient. You can get the start screen by using DS-R (double shift R) in instance 0 / config screen.

Okay - time to load up a more detailed documentation for it.

Here you find the attached ZXblast user manual.

Now if I only had a 'blast to go with the manual...Saving my pennies.