Composite modding a TK-83
Hi everybody,
Perhaps you can help me. I've just modded my Jupiter Ace 4000 to composite video and it worked a treat, so I thought I'd try one of my ZX81 clones, as their video is normally too weak for my TVs.
So, here's my TK-83. The modding process went smoothly, though it was a bit more of a headache because of the weird modulator internals. The problem is that the display is too dark, and the characters are a bit distorty. I'm suspecting there may be a lack of back porch like the ZX80s suffer from. The picture of the display is with brightness and everything turned up full, at normal settings it's much much darker.
Anybody have any ideas? Images are:
Thanks for any help!
Edit: the mod I did was http://www.zx81.de/english/video_e.htm - using a BC547C with a 75R resistor (tried with a pot too just in case).
Edit2: Yes, it's a TK-85, not a TK-83. The '83 gets done once the '85 is working acceptably!
Perhaps you can help me. I've just modded my Jupiter Ace 4000 to composite video and it worked a treat, so I thought I'd try one of my ZX81 clones, as their video is normally too weak for my TVs.
So, here's my TK-83. The modding process went smoothly, though it was a bit more of a headache because of the weird modulator internals. The problem is that the display is too dark, and the characters are a bit distorty. I'm suspecting there may be a lack of back porch like the ZX80s suffer from. The picture of the display is with brightness and everything turned up full, at normal settings it's much much darker.
Anybody have any ideas? Images are:
Thanks for any help!
Edit: the mod I did was http://www.zx81.de/english/video_e.htm - using a BC547C with a 75R resistor (tried with a pot too just in case).
Edit2: Yes, it's a TK-85, not a TK-83. The '83 gets done once the '85 is working acceptably!
Post edited by Spirantho on
Comments
Same on my Timex1000 (ZX81). Picture is fine on another TV though.
Is that the same problem? Maybe I need to find the sync signal and do the back porch mod on it...