Various ZX81 Items on SellMyRetro.com

[1024MAK]

http://forum.tlienhard.com/ts1000/www.t ... 942504.htm
http://forum.tlienhard.com/ts1000/www.t ... 564648.htm
http://forum.tlienhard.com/ts1000/www.t ... U-BERT.htm

[yerzmyey]

Btw 1024MAK, how did You find required posts on the archive? Any engines don't work or require log-in which is obviously impossible.

[Paul]

Google??

[gozzo]

Yes, I've tried google, and already seen those ts1000. posts, and also have a possibly complete copy of the www.ts1000.us, .... just got to keep trying now and again I suppose,... hoping that something may turn up......

[1024MAK]

Btw 1024MAK, how did You find required posts on the archive? Any engines don't work or require log-in which is obviously impossible.

Yes, I used Google. I used the advanced search.
I searched for

Compusa site:http://forum.tlienhard.com/ts1000/www.ts1000.us

https://www.google.co.uk/search?hl=en&a ... as_rights=

Mark

[yerzmyey]

Thx.

[gozzo]

Still haven't yet tested it but have examined it further - the 'triple piggyback' is of 2 2716 2kb eproms with one gate of a 74ls14 wired between each eproms CE line,one of them thats connected to the input of the gate connected to the board going to the A11 line of the ZX, and both OE's tied to ground - obviously they didn't have any 2732's (4kb) they could have used (track cuts and added wire links suggest a 2732 was intended)- but as for why TWO eproms (other one a single 2716) ?? not yet sure - maybe one is used as a 'data-separator' - I've heard of a fusible link PROM chip being used in such a circuit (got it somewhere..) to add a disk interface to a speccy +2A...??? I think (but am not yet 100% sure) that the added switch is probably to disable the interface..

[sirmorris]

I'm looking forward to your analysis of this board! It looks like there's enough there to keep you intrigued for a while

Dumps of the roms would be interesting. I see the problem with them being soldered in though. You'd have to make a dumper that plugs in to the expansion connector. That would be a cool little project in itself..! If, like you think, one of the eproms is used as a logic array then that probably won't dump from the expansion

C

[gozzo]

The eproms themselves aren't soldered to the board - they ARE in sockets (phew!) but all the other chip are (damn!), although 2 of the eproms are soldered together as part of a triple piggyback, but it appears to be wired to simulate a 2732 out of 2 2716's !!! There are 2 big problems - the other chips being soldered in, as said above(pain in the bum to change/test if they are duff), and my eprom programmer can only handle 2764 or higher , unless I can rig some sort of adapter up (although I have now ordered one through ebay which supposedly handles 2716 and higher!), and it cant program/reprogram them as its highest program voltage is 12.5 and as far as I know 2716/2732' s use either 21 or 25 v.. Don't yet know when I'll be able to test it (hopefully within a few days) as I have just got hold of some more stuff I need to sort out first (2 fairly old laptops, some ISA pc cards,a commodore A1200, and some valves(!!) )..

[Moggy]

I have the opposite problem My spectrum eprom burner can handle the 21v stuff and not the 12.5v 2764s only the 25v ones


Moggy.