Search found 992 matches

by Paul
Fri Sep 17, 2010 9:15 am
Forum: Hardware
Topic: ZX80 ROM in zx81?
Replies: 7
Views: 2643

Re: ZX80 ROM in zx81?

hi all, there is a way to get a ZX80 ROM running without problem without the need of cutting the NMI line. It is taken from the german ZX-Team forum, where it was posted recently by the original user holmatic: http://forum.tlienhard.com/phpBB3/viewtopic.php?f=2&t=412 The first instruction in a ZX81 ...
by Paul
Sun Aug 29, 2010 1:30 pm
Forum: Development
Topic: New ZX80 boards
Replies: 194
Views: 99069

Re: New ZX80 boards

After his last visit, Jens found out that every line is shifted by one "Subrow" upwards with Jumper 5-6 set. You can see this quite good using the shift-S Character as all lines are used there It is the same with my board, with ZX80 and ZX81 rom. Is this the same on the other boards? @Lee, has this ...
by Paul
Sun Aug 01, 2010 10:07 pm
Forum: Development
Topic: New ZX80 boards
Replies: 194
Views: 99069

Re: New ZX80 boards

Yes, correct no connection to the pad of R30. Thanks for the description, this explains why nothing happened to the signal level: R32 is exactly in the middle position, I forgot to try to change its setting :oops:, or even to compare their settings, because there is absolutely no problem with my mon...
by Paul
Sun Aug 01, 2010 7:35 pm
Forum: Development
Topic: New ZX80 boards
Replies: 194
Views: 99069

Re: New ZX80 boards

Hi Lee, I also misinterpreted the photo. Luckily I could see #4 in live. The yellow wire connects the additional diode directly from R37 to D13, no connection to R31. I hope that makes it clear. Why my modification from 1K to 500 Ohm did not increase the video level I cannot tell. I checked the valu...
by Paul
Fri Jul 23, 2010 2:48 pm
Forum: Development
Topic: New ZX80 boards
Replies: 194
Views: 99069

Re: New ZX80 boards

Neither good nor bad. At the moment 4 out of 5 Boards are completely built. One does not work (Jens), it gives no signal to the screen, there will be further investigation this weekend. Two work with the known error of the keyboard. SirMorris replaced the diodes with no effect. My board still works ...
by Paul
Mon Jul 05, 2010 6:41 pm
Forum: Development
Topic: New ZX80 boards
Replies: 194
Views: 99069

Re: New ZX80 boards

I made a EEPROM with ZX81 + ZX80 + ZX80 ROM inside and tried out a bit. The printing near w5 doesn't seem to match the schematics. There is 5V at '27128' where should be A13, and A13 at '2732' where should be 5V. The schematic also states 2716 here, where it should read 2732 like on the board. This ...
by Paul
Sun Jul 04, 2010 9:59 am
Forum: Development
Topic: New ZX80 boards
Replies: 194
Views: 99069

Re: New ZX80 boards

Hi SirMorris, I'm using BAT41. It took me a quarter of an hour to find this out. I had to use the power of two magnifying glasses :oops: It is 100V 100mA. The voltage drop of mine were between 291mV and 316mV. The datasheet lists them with 0.4V But I didn't select them. I just went to my local elect...
by Paul
Sat Jul 03, 2010 10:46 am
Forum: Development
Topic: New ZX80 boards
Replies: 194
Views: 99069

Re: New ZX80 boards

Thanks for your reply, Lee. Yes, the keyboard works with all shifted keys as well. So the diode drop was the problem (or my configuration works for any other reason). We will know for shure if superfoe or SirMorris replaces the diodes and this solves their problem. No, there was no jumper installed ...
by Paul
Fri Jul 02, 2010 11:52 pm
Forum: Development
Topic: New ZX80 boards
Replies: 194
Views: 99069

Re: New ZX80 boards

Hi all, just in case you'd like to know: my ZX80 is ready and it's working. Does that make it serial# 3? The keyboard works without problems, I used schottky diodes instead of 1N4148 for the keyboard. There is a tiny problem with the display: Every displayed line begins with pixel line #2, followed ...
by Paul
Fri Jul 02, 2010 7:52 am
Forum: Development
Topic: New ZX80 boards
Replies: 194
Views: 99069

Re: New ZX80 boards

Hi all,
after a few hours of sleep I was able to read the schematics again. :oops:
Q1 is 2N3906 and Q2 is 2N3904. :)
So I will finish my soldering this evening and give it a try.

Paul