Hi all
First post on the forum! I recently resurrected my ZX-81 that I bought new with my hard-earned savings as a teenager back when it first came on the market. I've replaced the keyboard, installed 16K RAM and installed a composite video (with backporch) board from zxrenew.co.uk and am feeding video to a composite to HDMI adapter for display on a computer monitor. I'm using a Maxduino to load software.
Here's the issue: occasionally the monitor screen goes blank and comes back again after a second or two. I'm guessing it doesn't like something about the video signal (adjusting the pots on the board). The screen also goes blank when loading a program but I suspect this is normal.
Anyway, I decided to connect to the composite video input of an old CRT TV that I had to compare - no issues with this, picture is completely stable so I'm thinking it's simply more tolerant on whatever fluctuations might be happening with the signal. However, I cannot load programs successfully while connected to the TV! I see the bars on the screen, but the loading process fails every time (bars stay on the screen when the Maxduino has finished playing). If I go back to the HDMI adapter/monitor programs load fine. I can even load while connected to the monitor, then when loaded, switch over to the TV and it remains ok - it's just the loading that's a problem.
My theory is that having the video output connected to the TV input is somehow 'loading' the signal and degrading it somehow. Has anyone seen anything like this before and/or have any ideas?
Thanks!
issue loading program while video output is connected to TV
- 1024MAK
- Posts: 5103
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: issue loading program while video output is connected to TV
Hello and welcome ploughna
I’m not sure what’s going on. Do keep in mind that some video receivers/converters/modern TVs don’t like the ‘strange’ to them signal that the computer produces when loading. As it’s very far from being a standard video signal.
The ZX81 ULA does use the video output pin for both the video generation and the signal for saving (MIC). But the ULA has a separate tape input pin (for the cassette EAR). So it should not be affected by whatever video receivers/converters or TV is connected.
Is your TV a double-insulated type (no earth pin connection on the mains plug)?
Have you tried loading from a real cassette tape?
Mark
I’m not sure what’s going on. Do keep in mind that some video receivers/converters/modern TVs don’t like the ‘strange’ to them signal that the computer produces when loading. As it’s very far from being a standard video signal.
The ZX81 ULA does use the video output pin for both the video generation and the signal for saving (MIC). But the ULA has a separate tape input pin (for the cassette EAR). So it should not be affected by whatever video receivers/converters or TV is connected.
Is your TV a double-insulated type (no earth pin connection on the mains plug)?
Have you tried loading from a real cassette tape?
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
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Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: issue loading program while video output is connected to TV
thanks for the quick reply. yes, TV is double-insulated and no, I haven't tried a real cassette tape (I don't have one anymore!)
Honestly, I'm not overly concerned about the TV if I can make the HDMI converter work more reliably. I might just buy another brand for comparison as they're very cheap (the one I have is called AV2HDMI - I bought this one as I saw it referenced by a few people here on the forum)
Honestly, I'm not overly concerned about the TV if I can make the HDMI converter work more reliably. I might just buy another brand for comparison as they're very cheap (the one I have is called AV2HDMI - I bought this one as I saw it referenced by a few people here on the forum)
- 1024MAK
- Posts: 5103
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: issue loading program while video output is connected to TV
I only mention the TV being double insulated, as sometimes the system not having a mains earth connection can affect things. Yes, it shouldn’t, but…
Mark
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.