ZXblast - ZX81 memory extension plus USB

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81
rcade
Posts: 16
Joined: Tue Dec 02, 2014 2:28 pm

Re: ZXblast - ZX81 memory extension plus USB

Post by rcade » Tue Feb 14, 2017 2:59 am

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?

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PokeMon
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Joined: Sat Sep 17, 2011 6:48 pm

Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon » Tue Feb 14, 2017 10:46 am

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 ?

rcade
Posts: 16
Joined: Tue Dec 02, 2014 2:28 pm

Re: ZXblast - ZX81 memory extension plus USB

Post by rcade » Tue Feb 14, 2017 4:19 pm

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.

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Andy Rea
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Location: notts UK

Re: ZXblast - ZX81 memory extension plus USB

Post by Andy Rea » Tue Feb 14, 2017 5:00 pm

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
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

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PokeMon
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Joined: Sat Sep 17, 2011 6:48 pm

Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon » Tue Feb 14, 2017 6:46 pm

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.

rcade
Posts: 16
Joined: Tue Dec 02, 2014 2:28 pm

Re: ZXblast - ZX81 memory extension plus USB

Post by rcade » Tue Feb 14, 2017 7:27 pm

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.

rcade
Posts: 16
Joined: Tue Dec 02, 2014 2:28 pm

Re: ZXblast - ZX81 memory extension plus USB

Post by rcade » Wed Feb 15, 2017 1:58 am

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!

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PokeMon
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Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon » Wed Feb 15, 2017 11:02 am

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. ;)

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PokeMon
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Re: ZXblast - ZX81 memory extension plus USB

Post by PokeMon » Thu Feb 16, 2017 7:52 pm

Here you find the attached ZXblast user manual. ;)
ZXblast-UserManual_V10.pdf
(692.91 KiB) Downloaded 95 times

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gammaray
Posts: 586
Joined: Sun Apr 17, 2016 2:44 am
Location: Texas

Re: ZXblast - ZX81 memory extension plus USB

Post by gammaray » Thu Feb 16, 2017 8:12 pm

Now if I only had a 'blast to go with the manual...Saving my pennies.
5-TS1000,UK ZX81<-Sheelagh, US ZX81, 2-TS1500/KDLX , 3-TS2040 printer, 2-TS2020 cassette decks, ZXPAND+AY, ZeddyNET, ZXBlast, UDG, ZX8CCB, AERCO, BUILDS/REPAIRS ZX Spectrum, ZX80 Minstrel, ZXMAX48 v1 v2, 2-TS-2068, ROM, 16kRAM

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