Page 4 of 5

Re: ZX80 3K Ram Pack memory

Posted: Wed Apr 18, 2018 11:03 am
by msch
1-3k-rampack.jpeg
iss1-partsside-pcb.jpeg
iss1-solderside-pcb.jpeg
partsside.jpeg
soöderside.jpeg
The blank PCB is a "Replica"-PCB based on the original one.

Re: ZX80 3K Ram Pack memory

Posted: Wed Apr 18, 2018 11:18 am
by msch
1-3k-rampack-pcb-both-sides.jpg

Re: ZX80 3K Ram Pack memory

Posted: Wed Apr 18, 2018 2:07 pm
by 1024MAK
If you want to compare the board to a schematic, I have found these two different versions:

This version is by Phill (Prime) on this forum, (link to post).

This version I found in a link from a post by Markus on forum.tlienhard.com (link to forum page) link to zip file.

Neither shows any connection between edge-connector contact 23B and 0V/GND.

Mark

Re: ZX80 3K Ram Pack memory

Posted: Wed Apr 18, 2018 2:24 pm
by mhudson52
Charlie, you beat me to it by 2 minutes! :lol:

Re: ZX80 3K Ram Pack memory

Posted: Wed Apr 18, 2018 2:26 pm
by msch
Thanks!

Re: ZX80 3K Ram Pack memory

Posted: Mon Apr 30, 2018 3:56 pm
by mhudson52
The ZX80 3K memory pack reproduction has just been posted on the SMR site. Thanks to everyone here for your generous help and advice! :D

Re: ZX80 3K Ram Pack memory

Posted: Mon Apr 30, 2018 4:19 pm
by Paul
mhudson52 wrote: Mon Apr 30, 2018 3:56 pm The ZX80 3K memory pack reproduction has just been posted on the SMR site. Thanks to everyone here for your generous help and advice! :D
Hi Mike, I had to search a while. Would you be so kind to also list it in the ZX80 section?
And it extends the internal ram by up to 3 k giving a total of 2 to 4 k of RAM.
Kind regards Paul

Re: ZX80 3K Ram Pack memory

Posted: Mon Apr 30, 2018 4:29 pm
by mhudson52
Hi Mike, I had to search a while. Would you be so kind to also list it in the ZX80 section?
And it extends the internal ram by up to 3 k giving a total of 2 to 4 k of RAM.
Will do, Paul, and thanks for the 4K reminder. The SMR listing has been updated.


Thanks,
Mike

Re: ZX80 3K Ram Pack memory

Posted: Thu May 03, 2018 12:53 am
by 1024MAK
1024MAK wrote: Tue Apr 17, 2018 12:32 amHmm. I have a TS1000 around he somewhere. I can't remember if it works, I think it has been modified to run at 50Hz. I also have a 3k RAM pack around somewhere. I'm working late turn shifts through to Thursday, then I'm away Friday and Saturday. So it will be a while before I can dig them out. If the TS1000 works, I'll post any findings here.
1024MAK wrote: Tue Apr 17, 2018 12:32 amI was expecting the circuitry in the 3k RAM pack to treat the existing 2k RAM chip in the TS1000 the same as it treats the 1k RAM chip in the ZX80 and ZX81. The end result being a total of 4k bytes of useable RAM (it's the decoding circuit that decides the memory map, not just the RAM chips themselves).
Well, about time for an update... :mrgreen:

My TS1000 has indeed been modified to work at 50Hz video. The keyboard membrane tails are shot. But never mind, I'm using a Memotech keyboard ;). Also, as the modulator is a VHF type, I'm using one of PokeMons ZX8 CCB modules to get a nice clear composite video output :D
Result of a check of the memory in a (more or less) standard TS1000
Result of a check of the memory in a (more or less) standard TS1000
I also tracked down my 3K byte RAM pack. Now, I should mention that this is a recreation and not an original. However, this reproduction did faithfully include the track connecting the 0V/GND to the edge-connector pin 23B.

With this track intact, the TS1000 does not work properly. Instead I get a rolling pattern of white dotted lines on a black background.

With the offending track cut, the 3K byte RAM pack works fine, as you can see from the photo below:
And with a (slightly) modified 3K byte RAM pack added to a TS1000
And with a (slightly) modified 3K byte RAM pack added to a TS1000
The set-up, a TS1000, Memotech keyboard interface and keyboard and a 3K byte RAM pack.
The set-up, a TS1000, Memotech keyboard interface and keyboard and a 3K byte RAM pack.
:D

Mark

Re: ZX80 3K Ram Pack memory

Posted: Thu May 03, 2018 2:32 pm
by mhudson52
Thanks for getting back to me Mark. Unless I just don't know what to look for ( a distinct possibility) there does not appear to be anything going to 23B on the Brenner design I am using. Take a look below and see if that is correct.
3K RAM Pack Front.JPG