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Timex Sinclair 1000 repair help needed.

There are 2 part numbers for the ULA chip.

2C184E - Older version. Missing the "back porch" part of the NTSC signal resulting in incompatibility with some TVs and most LCD displays.

2C210E - fixed that signalling issue.

You can buy a 3rd party composite video converter for the ZX81 / TS1000 that fixes the missing back porch part of the NTSC signal. I highly recommend going that route rather than trying to fix it yourself if that is your problem.
 
channelmaniac said:
There are 2 part numbers for the ULA chip.

2C184E - Older version. Missing the "back porch" part of the NTSC signal resulting in incompatibility with some TVs and most LCD displays.

2C210E - fixed that signalling issue.

You can buy a 3rd party composite video converter for the ZX81 / TS1000 that fixes the missing back porch part of the NTSC signal. I highly recommend going that route rather than trying to fix it yourself if that is your problem.
Click to expand...
I have both chips between 2 diff systems, I think the newer one is bad, no signal by the look of it. I found one, https://www.tindie.com/products/charlieingley/vla81-zx81-ula-replacement/ I can use it for either option with added switches, not as if I'd turn off the Backporch, but good to know I could if I needed to.
xp0nentz said:
Oh, Nothin? Strange.
Click to expand...
It might be cause the one with the workingish display don't have the backporch signal?
 
jknightandkarr said:
I have both chips between 2 diff systems, I think the newer one is bad, no signal by the look of it. I found one, https://www.tindie.com/products/charlieingley/vla81-zx81-ula-replacement/ I can use it for either option with added switches, not as if I'd turn off the Backporch, but good to know I could if I needed to.

It might be cause the one with the workingish display don't have the backporch signal?
Click to expand...
On my tv with my rf zx81, when color is turned to 0 it inverts the colors.
 
xp0nentz said:
Hm, strange. Could you send an image?
Click to expand...
I posted one while back, page 2, post #24. It don't differ from that photo.
channelmaniac said:
When you have the ULA with the missing back porch signal on NTSC it gives a very dark display when the TV can't handle it.
Click to expand...
I probly need to upgrade the ULA with that one in the link above.... my other unit has the newer chip, but I am pretty sure it's bad, I did a swap and nada....
 
Well the place I WAS going to get stuff from isn't shipping to USA due to tarrifs.... so I guess other then Ebay, anyone got places I can get the modern ver of the ULAs and the Composite Mods with the adjustments? I've not had much luck with search results...
 
jknightandkarr said:
I posted one while back, page 2, post #24. It don't differ from that photo.

I probly need to upgrade the ULA with that one in the link above.... my other unit has the newer chip, but I am pretty sure it's bad, I did a swap and nada....
Click to expand...
Very strange. My tv inverts colors when color is 0.
 
This is probably a function of your TV. It would not be the norm...

The colour (chroma) signal is modulated on top of the luma signal.

Disabling the colour should leave the (unmodified) luma signal in place for the monochrome display.

Dave
 
daver2 said:
This is probably a function of your TV. It would not be the norm...

The colour (chroma) signal is modulated on top of the luma signal.

Disabling the colour should leave the (unmodified) luma signal in place for the monochrome display.

Dave
Click to expand...
I turned my color to 0, and no change. I think its due to the lack of a backporch signal, and maybe my composite mod
 
xp0nentz said:
Very strange. My tv inverts colors when color is 0.
Click to expand...
It might be due to my ULA not having a backporch signal. I'm looking at options online. Sadly the link I posted above, which I was going to get adj composite mod and ula, offers no shipping to USA.....
 
Sinclair's hardware definitely played loose with the specifications, and it would have problems with some TV sets, even with the PAL system used in the UK. My Issue 2 ZX Spectrum simply didn't work properly with one of our TVs - although there was a picture, the colours other than blue were completely wrong. This was due to PAL inverting the phase of alternate lines in the signal in an attempt to get around need for a tint control under NTSC - somehow the TV ended up inverting the phase of the wrong lines.
 
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