Search found 2582 matches

by 1024MAK
Sun Dec 15, 2019 7:43 pm
Forum: Hardware
Topic: Earliest known ZX81?
Replies: 5
Views: 76

Re: Earliest known ZX81?

Erm wrote:
Sun Dec 15, 2019 6:27 pm
Mentioned in another recent topic, but I thought I'd share it here so that people can find and add details of early ZX81's.

This one is very early, so I have bragging rights for now ;).
Sorry, when I started reading this post, I thought it was Lardo with yet another Zeddy :lol:

Mark
by 1024MAK
Sun Dec 15, 2019 5:48 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 20
Views: 208

Re: vLA81 ULA and 16/32K internal RAM

Lardo Boffin wrote:
Sun Dec 15, 2019 5:29 pm
I quite liked the Sinclair ROM bodge
:shock: Image

You mean ‘mandatory modification’ surely :lol:

Mark
by 1024MAK
Sun Dec 15, 2019 3:30 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 20
Views: 208

Re: vLA81 ULA and 16/32K internal RAM

Presumably the major issue with bent pins on an IC is that it makes maintenance more difficult in the future? Would it be possible to fit a low profile socket, then fit another socket (pins bent out) and put the IC in that? Only the sandwich socket is modified and the RAM chips are easily swappable...
by 1024MAK
Sun Dec 15, 2019 12:24 am
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 20
Views: 208

Re: vLA81 ULA and 16/32K internal RAM

Top of ZX81 PCB showing temp +5V wire link to be removed.
Top of ZX81 PCB showing temp +5V wire link to be removed.
Bottom of ZX81 PCB showing signal details including A14
Bottom of ZX81 PCB showing signal details including A14
Bottom of ZX81 PCB showing wiring and added A14 wire
Bottom of ZX81 PCB showing wiring and added A14 wire
Mark
by 1024MAK
Sat Dec 14, 2019 10:46 pm
Forum: Hardware
Topic: I got a ZX80!
Replies: 7
Views: 104

Re: I got a ZX80!

That’s a nice looking ZX80 8-)

In relation to the ROM and EPROMs, check out this useful page ;-)

Mark
by 1024MAK
Sat Dec 14, 2019 10:13 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 20
Views: 208

Re: vLA81 ULA and 16/32K internal RAM

Thank for the links. I was wondering how using one of these to get 32K would work in relation to your mod process? Presumably the same tracks would be cut. Would the part where you reconnect the two cut tracks be connected directly to a pin on the vLA? https://www.sinclairzxworld.com/download/file....
by 1024MAK
Sat Dec 14, 2019 10:08 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 20
Views: 208

Re: vLA81 ULA and 16/32K internal RAM

I've done a few of these (and have done a lot of fiddling with various configurations and written a lot of emails bothering Mr Ingley with silly questions) and there is no need to cut any tracks, just bend out 4 pins (1,2,23,26) of the 32k RAM chip and connect to address lines A11 to A14. Note that...
by 1024MAK
Sat Dec 14, 2019 3:46 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 20
Views: 208

Re: vLA81 ULA and 16/32K internal RAM

More help about the vLA81 ZX81 ULA in these threads

The maker describes the vLA81

soft mode changes

I must find time to play with mine some more :oops:

Mark
by 1024MAK
Fri Dec 13, 2019 9:22 pm
Forum: Hardware
Topic: Garbled display when certain keys are pressed.
Replies: 5
Views: 123

Re: Garbled display when certain keys are pressed.

This fault is almost always due to the ULA...

Mark
by 1024MAK
Thu Dec 12, 2019 4:41 pm
Forum: Development
Topic: New ZX80 cases
Replies: 12
Views: 251

Re: New ZX80 cases

The difficult factor here is predicting quantity, on small runs the price is X amount, if i order double, it comes down, if i order 5 times the amount, the price comes close to 50% Yeah, I’m aware that the order volume affects the unit cost. Have you posted on the other Sinclair / ZX Spectrum forum...