Search found 15 matches

by inaki
Fri Dec 20, 2013 7:24 pm
Forum: Hardware
Topic: I got the ZX80 Replica Kit
Replies: 1
Views: 1473

I got the ZX80 Replica Kit

Hi, I got the Z80 Replica Kit selling on eBay, from Bulgaria. It took 3 weeks to arrive ! It is a very nicely presented and clean kit. As always happens with any kit, it is a shame to assemble it! :-) I miss having a case though. Anyone with a 3D printer wanting to take the challenge to print a ZX80...
by inaki
Tue Dec 17, 2013 1:37 am
Forum: Hardware
Topic: ZX81 White display
Replies: 17
Views: 4207

Re: ZX81 White display

Thanks everyone to point out possible checkings. I will try to check it all. However, having replaced every active component (every chip and the two transistors), is it not strange I get exactly the same behavior than using the original components ? I mean, would it not point to some passive compone...
by inaki
Fri Dec 13, 2013 9:34 pm
Forum: SALES
Topic: ZX81 with a serial number...
Replies: 11
Views: 6753

Re: ZX81 with a serial number...

Here a ZX81 with ULA 82-45. No serial number.
by inaki
Thu Dec 12, 2013 9:02 pm
Forum: Hardware
Topic: ZX81 White display
Replies: 17
Views: 4207

Re: ZX81 White display

Tried with 16K pack. No changes.
by inaki
Wed Dec 11, 2013 10:10 pm
Forum: Hardware
Topic: ZX81 White display
Replies: 17
Views: 4207

Re: ZX81 White display

I have taken a look at the thread where pokemon explains the shape I should get on A15. I get a similar pattern to the one in the pictures for a couple of seconds. Then the signals starts changing. Some seconds later the signal is flat. So it seems clear to me that some component is heating up and t...
by inaki
Wed Dec 11, 2013 9:33 pm
Forum: Hardware
Topic: ZX81 White display
Replies: 17
Views: 4207

Re: ZX81 White display

gozzo, I have replaced both TR133 with new ones. No way. Same white display! :-(

iturbez, I will check RAM connections and will take a look at these scope signals too. Thanks!
by inaki
Wed Dec 11, 2013 6:56 pm
Forum: Hardware
Topic: ZX81 White display
Replies: 17
Views: 4207

Re: ZX81 White display

I have checked the NMI.
It is alive for a couple of seconds and then vanishes.
The edge an frequency of the NMI pulse matches the start video signal. Is this right? The pulse is 5us wide.
I can figure out the NMI should last forever, unless fast mode is used, right ?
by inaki
Wed Dec 11, 2013 3:50 pm
Forum: Hardware
Topic: ZX81 White display
Replies: 17
Views: 4207

Re: ZX81 White display

I have not replaced the ROM because apparently it reads well and the code matches the one I can see on the available ZX81 ROM listings. I do know the system is working because I see it working when I connect it to a Z80 ICE. I can actually see the startup code running. The TV modulator appears to wo...
by inaki
Tue Dec 10, 2013 6:20 pm
Forum: Hardware
Topic: ZX81 White display
Replies: 17
Views: 4207

ZX81 White display

I am trying to get to life my old ZX81 in kit. Apparently it is working but display is white. No cursor, no characters. Just a white background. I have checked the video output with a scope and it looks right. The display is a well formed white rectangle. The Z80 apparently is running fine. I have c...
by inaki
Mon Dec 09, 2013 7:14 pm
Forum: Development
Topic: ZX80 Core - new ZX80 motherboards
Replies: 259
Views: 62932

Re: ZX80 Core - new ZX80 motherboards

Of course, I am not interested in machines that work at first try!
Said this, I do not like these opaque soldering mask. I prefer the transparent ones.

inaki.