Sinclair ZX80 / ZX81 / Z88 Forums

Hi,

Im looking for some help. I have a MR-X sound card. The GAL chip on it got very warm and it no longer works.

As there are only two ICs - GAL and AY sound chip it should be an easy fix, except I cant source the GALs.

Is there anyone who could program a GAL for me? I'll be happy to pay for the GAL, any post and packing costs and even buy a beer*.

* Other drinks are available

Thanks,

Dave

I'm sure I can help if I can get hold of the JED (programming) file. I can ask Sasha, one of the German ZX-team. I _think_ this was his board design.

Hello Charlie

If you know Sasha and he can help its possibly easier and quicker. Let me know how much I'll owe you. Can I pay by Paypal?

Otherwise I'll try to get the JED file.

Thanks a lot,

Dave

I have emailed Sascha - yes, he designed and makes these sound interfaces

Thanks Rich, couldn't ask for more.

Dave

well these are two reasons why I try to avoid using programmable (PAL/GAL) devices, they may be easy to use, and to change if you are uncertain of what they should do, (for example which addresses to decode and how to control the PSG chip) but they do break down, and if they do you have to be able to get their contents to repair them. not so good if you want to preserve the information for eternity.

I'm actually in the process of designing my own ZON x-81 compatible PSG for my ZX81+35 clone, and it has been a puzzle to find out details, like clock frequency, and I/O addresses, and such things, the (preliminary) result of my efforts (schematic) can be found here: https://revspace.nl/ZX81%2B34_ZX81_clon ... sion_board

I knew about the mr-x soundcard and have been curious about further details, but just as details about other PSG systems for the ZX81 they are hard to get and some sources are contradictory.

For example, does the son x-81 use 1.625MHz, or something like 100KHz as a clock?

I want to create a zon x-81 clone where you can also read from the PSG registers, would that be possible?

Yes. ZXpand-AY allows this, whilst remaining compatible with the original zon-x. The source code for EO is a good reference for things like IO addresses. Or you could ask here...

Hello,

I got a Mail from Rich and a PN from SirMorris. I will send him the JED files this weekend. He'll burn the GAL and ship it to you rune.

I will soon offer on my homepage those files, so that everybody can use them. Anyway they are public domain and for free .....

Regards
Sascha

mahjongg wrote:
...For example, does the son x-81 use 1.625MHz, or something like 100KHz as a clock?

1.625 is the sound chip frequency I use when setting Sergey Bulba's AY emulator to Zonx-81 mode and it sounds just right, if that helps.

Thanks Sasha,

SirMorris could you PM me when its ready and I'll send payment.

Thanks also to everyone else who commented or helped. This is why I think this forum is the best.

Dave