Search found 1910 matches

by 1024MAK
Wed Apr 18, 2018 2:07 pm
Forum: Hardware
Topic: ZX80 3K Ram Pack memory
Replies: 37
Views: 1017

Re: ZX80 3K Ram Pack memory

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 connect...
by 1024MAK
Tue Apr 17, 2018 8:11 pm
Forum: Hardware
Topic: ZX80 3K Ram Pack memory
Replies: 37
Views: 1017

Re: ZX80 3K Ram Pack memory

by 1024MAK
Tue Apr 17, 2018 7:39 pm
Forum: Hardware
Topic: ZX80 3K Ram Pack memory
Replies: 37
Views: 1017

Re: ZX80 3K Ram Pack memory

So looking at that page that Moggy helpfully provided, comparing it to a picture of a 3k RAM pack, and comparing it to the edge-connector details for both the ZX80 and the ZX81... It looks like the 3k RAM pack is linking edge-connector terminal 23B to 0V/GND. This does not matter on a ZX80, as this ...
by 1024MAK
Tue Apr 17, 2018 6:34 pm
Forum: Hardware
Topic: ZX80 3K Ram Pack memory
Replies: 37
Views: 1017

Re: ZX80 3K Ram Pack memory

Ahh, thank you Moggy :D

Mark
by 1024MAK
Tue Apr 17, 2018 2:35 am
Forum: Hardware
Topic: Sinclair 128k ZX Spectrum +2 Grey UK no video after inverted polarity
Replies: 10
Views: 166

Re: Sinclair 128k ZX Spectrum +2 Grey UK no video after inverted polarity

Note, the +12V and -5V are also on the edge-connector. If you have a regulated 12V supply, you could always feed it in via either the edge-connector, or via D20 cathode connection. Of course, check, test and double check the polarity ;) You still need a nominal +9V on the power jack input for the 78...
by 1024MAK
Tue Apr 17, 2018 12:32 am
Forum: Hardware
Topic: ZX80 3K Ram Pack memory
Replies: 37
Views: 1017

Re: ZX80 3K Ram Pack memory

Mark, I ran your code on my 2k TS1000 with the ram pack attached and got the exact same result as you :( , so I am assuming that something in it needs to be changed to work on the TS. Like I've said, I'm dumber'n a box of rocks when it comes to this stuff. Hmm. I have a TS1000 around he somewhere. ...
by 1024MAK
Tue Apr 17, 2018 12:26 am
Forum: Hardware
Topic: Sinclair 128k ZX Spectrum +2 Grey UK no video after inverted polarity
Replies: 10
Views: 166

Re: Sinclair 128k ZX Spectrum +2 Grey UK no video after inverted polarity

TR9 has to be a fast switching power transistor. I'm not sure a BC548 will work (the BC548 and similar transistors are for audio frequency low power amplifier applications). Certainly a BC548 will not last long in the 16k and 48k models (although in these there is a higher load on the +12V supply). ...
by 1024MAK
Mon Apr 16, 2018 7:49 pm
Forum: Hardware
Topic: Sinclair 128k ZX Spectrum +2 Grey UK no video after inverted polarity
Replies: 10
Views: 166

Re: Sinclair 128k ZX Spectrum +2 Grey UK no video after inverted polarity

It's likely that TR8 (ZTX213) and TR9 (ZTX650, or ZTX651 or ZTX653) have been damaged. I suggest replacing TR9 first. If you test across C41 connections (or between D20 cathode (K) and 0V/GND) when the internal DC/DC circuit is working correctly, your meter should show about +12V even if the input s...
by 1024MAK
Mon Apr 16, 2018 12:15 am
Forum: Development
Topic: ZX81 ULA-in-a-CPLD
Replies: 147
Views: 12159

Re: ZX81 ULA-in-a-CPLD

@Andy - naughty but nice :D

Mark
by 1024MAK
Mon Apr 16, 2018 12:04 am
Forum: Welcome Area
Topic: Hello from Portugal
Replies: 1
Views: 56

Re: Hello from Portugal

Hello João

Welcome to our forum :D

All the Sinclair computers are polarity sensitive.

I suggest you post details of the problems you are having in the ZX Spectrum area of the site here ;)

Mark