Search found 41 matches

by zx-heinz
Thu Aug 12, 2021 3:45 pm
Forum: Hardware
Topic: VLa81 noisy video signal
Replies: 19
Views: 4112

Re: VLa81 noisy video signal

Change the capacitor C2 (located close to the modulator) into a bigger one, 100nF or 1µF.
by zx-heinz
Tue Aug 10, 2021 6:31 pm
Forum: Hardware
Topic: VLa81 noisy video signal
Replies: 19
Views: 4112

Re: VLa81 noisy video signal

Check the Ground Line. Do you have noise between the ground at the modulator and the ground at the 7805 regulator (heat sink)?
by zx-heinz
Fri Jun 25, 2021 3:20 pm
Forum: Hardware
Topic: ZX81 Troubleshooting
Replies: 13
Views: 5164

Re: ZX81 Troubleshooting

Check also the signal at CPU/18(=HALT) and ULA/17(=HALT) as well as the signals around TR1.
by zx-heinz
Thu Jun 24, 2021 5:07 pm
Forum: Hardware
Topic: ZX81 Troubleshooting
Replies: 13
Views: 5164

Re: ZX81 Troubleshooting

Try a different CPU or look for shorts around pin17. (I use a Andy Rea's ULA).
by zx-heinz
Fri Apr 02, 2021 10:55 am
Forum: Hardware
Topic: Power consumption and the voltage regulator
Replies: 6
Views: 2275

Re: Power consumption and the voltage regulator

Hi patters,
look for Step Down regulators at e Ba* as an alternative.
by zx-heinz
Thu Apr 01, 2021 11:12 pm
Forum: Hardware
Topic: Power consumption and the voltage regulator
Replies: 6
Views: 2275

Re: Power consumption and the voltage regulator

Hello patters, we've detected the same problem in https://forum.tlienhard.com/phpBB3/viewtopic.php?p=49046#p49046 . The internal regulator will be overheated. A switching regulator is strongly recommended to overcome this problem. I usually use cheap Chinese step down regulators as shown in the pict...
by zx-heinz
Sun Mar 21, 2021 4:55 pm
Forum: Software
Topic: Pascal for ZX81
Replies: 71
Views: 20548

Re: Pascal for ZX81

It seems there is no direct way to write a program, to compile it afterwards and run immediately. You have to save in between. Is this true or am I wrong?
by zx-heinz
Sun Mar 07, 2021 12:30 pm
Forum: GAMES
Topic: New ZX81 Games
Replies: 363
Views: 682054

Re: New ZX81 Games

@DrBeep: Thank you for assisitance, with WRX on EO it runs perfectly. Also on my ZX81NU, even with WESPI+Display. My score is 85 :D
by zx-heinz
Sat Mar 06, 2021 12:29 pm
Forum: GAMES
Topic: New ZX81 Games
Replies: 363
Views: 682054

Re: New ZX81 Games : Johnnie Walker

dr beep wrote: Fri Mar 05, 2021 10:00 pm Requirements (eg. 1K, 16K, AY Card, Hi-Res Scheme): 1K hires
Hello Dr. Beep,
unfortunately the game doesn't run with graphics on my EO. Just black blocks. Where can I get the Hi-Res Scheme?
Heinz
by zx-heinz
Fri Jan 29, 2021 11:54 pm
Forum: Hardware
Topic: ZX-81 Power supply question (USA)
Replies: 3
Views: 1252

Re: ZX-81 Power supply question (USA)

Don't worry, this PSU can be used. If there is no load then the voltage goes up by the factor sqrt(2)=1.41. So, 9.75V * 1.41 = 13.7V is near to your measured value. And since it is original, there is also no problem with the polarity.