Sinclair ZX80 / ZX81 / Z88 Forums

Hello folks,

After many years searching I finally got a working IQ8300 with a bonus of a boxed colour pack. No PSU, but since it's a ZX81 clone-esque with a 7805 regulator I checked the polarity and fed it 8v@1A and after a reset got a nice READY prompt on a composite monitor. Quick BASIC program entry and all is well.

Colour box is a different story though. I guessed that the flying lead was supposed to go into the Monitor socket since that's all it would reach (I hadn't RTFM at that point ), video cable into the Monitor socket on the box. There's no output though. The machine is working since I can type SOUND and get a noise, plus the random keyboard beeps work. Nothing on the monitor.

Reading the forum I saw the specs of the real PSU and noted that the colour box needs more current for it to work. Upping the voltage to 12v doesn't help my bench PSU isn't breaking a sweat, running at 400mA. It's set to limit at 1A.

Am I going wrong anywhere? I've now RTFM and it says I should get a picture no matter what.

Cheers!

I do remember having to put more power into the Lambda 8300, when I attached a Colour Pack.

My color monitor since has died, and my Lambda 8300 has become flaky, so I won't be able to test it now.

Did you get the Lambda from the Pink Hat Man? I managed to miss the end of the auction.

Lardo Boffin wrote: ↑Tue Sep 24, 2024 10:09 am Did you get the Lambda from the Pink Hat Man? I managed to miss the end of the auction.

It was indeed. I didn't expect to win it so was really pleased when I got the notification One more unicorn off my wants list, and something new to show at the next RetroFest.

mrtinb wrote: ↑Mon Sep 23, 2024 10:28 pm I do remember having to put more power into the Lambda 8300, when I attached a Colour Pack.

My color monitor since has died, and my Lambda 8300 has become flaky, so I won't be able to test it now.

I think it was your post about voltage boosting that I saw, but that's only usually necessary if the circuit is pulling more current than the PSU can provide. In my case my bench PSU sits at 400mA with the pack fitted. It's current limited to 1A so if the machine did need more current it would be obvious.

witchy wrote: ↑Tue Sep 24, 2024 11:29 am I think it was your post about voltage boosting that I saw, but that's only usually necessary if the circuit is pulling more current than the PSU can provide. In my case my bench PSU sits at 400mA with the pack fitted. It's current limited to 1A so if the machine did need more current it would be obvious.

I have no education in electronics. I just bought a multivoltage PSU. I sat in on 6V, and if the screen got unstable I changed to 9V, and again 12V. Usually the picture got stable at one of the voltages. It also depended on how warm the computer was. As I am not educated in electronics, I don't know what was going on. I just experienced that it sometimes fixed my problem.

mrtinb wrote: ↑Tue Sep 24, 2024 12:23 pm I have no education in electronics. I just bought a multivoltage PSU. I sat in on 6V, and if the screen got unstable I changed to 9V, and again 12V. Usually the picture got stable at one of the voltages. It also depended on how warm the computer was. As I am not educated in electronics, I don't know what was going on. I just experienced that it sometimes fixed my problem.

This is how we learn things I'm self taught too. Forums like this are a great source of knowledge transfer for me.

Now play MUSHROOMMAN with the brand new quaracterdisplay!

dr beep wrote: ↑Tue Sep 24, 2024 6:00 pm Now play MUSHROOMMAN with the brand new quaracterdisplay!

Hopefully my new *duino device will arrive tomorrow, after the demise of my original TZXduino/Arduitape. Then I can throw some 2k games at it.

witchy wrote: ↑Thu Sep 26, 2024 8:10 pm
Hopefully my new *duino device will arrive tomorrow, after the demise of my original TZXduino/Arduitape. Then I can throw some 2k games at it.

Well you can start with this demo

viewtopic.php?f=16&t=5558&p=55993&hilit ... res#p55993

or this generator
viewtopic.php?p=55967#p55967

You can load them by playing them over the soundcard right now.