ZX80 3K Ram Pack memory

Discussions about Sinclair ZX80 and ZX81 Hardware
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msch
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Re: ZX80 3K Ram Pack memory

Post by msch » Wed Apr 18, 2018 11:03 am

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.
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msch
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Re: ZX80 3K Ram Pack memory

Post by msch » Wed Apr 18, 2018 11:18 am

1-3k-rampack-pcb-both-sides.jpg
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1024MAK
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Re: ZX80 3K Ram Pack memory

Post by 1024MAK » Wed Apr 18, 2018 2:07 pm

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

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mhudson52
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Re: ZX80 3K Ram Pack memory

Post by mhudson52 » Wed Apr 18, 2018 2:24 pm

Charlie, you beat me to it by 2 minutes! :lol:
TS 1000 bought in 1982 and brought back to life by Sir Ian

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msch
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Re: ZX80 3K Ram Pack memory

Post by msch » Wed Apr 18, 2018 2:26 pm

Thanks!
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mhudson52
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Re: ZX80 3K Ram Pack memory

Post by mhudson52 » 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
TS 1000 bought in 1982 and brought back to life by Sir Ian

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Paul
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Re: ZX80 3K Ram Pack memory

Post by Paul » Mon Apr 30, 2018 4:19 pm

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
In theory, there is no difference between theory and practice. But, in practice, there is.

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mhudson52
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Re: ZX80 3K Ram Pack memory

Post by mhudson52 » Mon Apr 30, 2018 4:29 pm

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
TS 1000 bought in 1982 and brought back to life by Sir Ian

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1024MAK
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Re: ZX80 3K Ram Pack memory

Post by 1024MAK » Thu May 03, 2018 12:53 am

1024MAK wrote:
Tue Apr 17, 2018 12:32 am
Hmm. 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 am
I 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
IMG_6870.JPG
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:
IMG_6987.JPG
And with a (slightly) modified 3K byte RAM pack added to a TS1000
IMG_6989.JPG
The set-up, a TS1000, Memotech keyboard interface and keyboard and a 3K byte RAM pack.
:D

Mark

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mhudson52
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Re: ZX80 3K Ram Pack memory

Post by mhudson52 » Thu May 03, 2018 2:32 pm

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
Attachments
3K RAM Pack Rear.JPG
TS 1000 bought in 1982 and brought back to life by Sir Ian

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