Sinclair ZX80 / ZX81 / Z88 Forums

The ULA for the ZX81 has currently two replacements: Andy’s ULA vLA81 These are often cheaper than an original ULA, as the original ULAs are getting rarer. The replacement ULA often has added some of these features: M1NOT mod to enable machine language in high memory, that Sinclair intended for data...

New hiscore in 1 Karat

I'm grateful for all the help you all give me. I havn't had time to test all suggestions yet.

As mentioned in the first post, there is no sound when software that uses WRX graphics is used.

So it is software affected. And remember: Most of the hardware in ZX81 is software.

It works with the composite output of a Raspberry Pi, without the noise.

My plan is to use my Lambda 8300 with the custom ZX81 ROM. This will work without the noise.

Maybe I can make a modified ROM for the ZX81, that does not produce the sound. :-/

The sound does not change at all changing the contrast and brightness. And here is a picture without the lights turned off. Here the monitor is powered off as well. https://trello-attachments.s3.amazonaws.com/598af660300e0d55b35f5755/5a36e7929ce3cfa9702728e9/31620e482c7645106b270984f1bc0382/image.jp...

mrtinb, I am unfamiliar with MTASM and am curious about the graphics characters at the end of each line of the program. What do they mean? zx-splsh.jpg These chars are not shown, when you edit the source inside the assembler. You are not supposed to display the source this way, but it was just a li...

I have now opened the back of the monitor. I have taken 2 pictures of the back if the tube in operation. One picture was taken with no composite input, and the other when the text mode of ROM display routine is making the sound. You can see it is shining brighter and more blue, when the text mode is...

Eagle CSS40 System CSS-14 Series, CCTV System. Monitor Model P701 (HVM29XXAS4C).

Can't find anything about it.

Sound is off, when LISTing i FAST-mode, but the resumes, when picture is drawn again.

Hello again, Sorry but I couldn't get all information about it. Please to check : http://blog.retroleum.co.uk/electronics-articles/nebula-spectrum-ula-chip-replacement-module/ May it helps you? write to Phill, he will answer you properly. The price is pretty low compared with other solutions. Cheer...