Which video mod for composite?

[Dukes909]

Hey folks, I am getting back to my ZX-81's and T-1000's; decided there simply isn't enough room on the desktop for a CRT-TV now. I am going to do one of the composite mods on one of my Timex 1000's but not sure how to know which one to build. I don't know if mine has the "back porch" ULA or not; is there a way to tell, or does it even matter if I use the zigg.net 555 mod or 1024MAK's mod? I know both of these probably aren't reversible but I don't suppose that matters.
Cheers
Dukester

[dessony]

Dukes909,

Can you post a picture of the ULA here? The picture will help us determine whether you need a zigg.net 555 mod.

Thank you very much in advance.

DesSony

[Dukes909]

Here 'tis.

Cheers

[dessony]

Dukes909,

The good news, you don't need to be concerned about installing zigg.net 555 mod on your computer! You'll be fine with the 2C210E ULA's back porch "stairway" wave presence!

I do have a 1024MAK's mod with my stripboard design on one of the forums. Please don't hesitate to get in touch with me, if you are interested.

Cheers,

DesSony

[Dukes909]

So I need to do the 1024MAK mod instead of the 555? I don't follow about your stripboard design; is it different from the one in 1024MAK's sig?; please expand on that. Also, how did you determine I don't need the 555 mod? I assume there is some clue in the ULA part number. I am having trouble keeping track of what needs what anymore..lol.
Cheers

[dessony]

No, You leave the ULA chip alone. You are fine now! There are 3 versions of ULA. The first two ULAs are buggy because they don't have their back porches feature yet. The final version [2C210E] had its back porch feature. 1024MAK has his better explanation on these ULAs' details somewhere on this forum. I bet that 1024MAK will concur on this one! Better forget about the 555 zigg.net mod. I have a few TS1000s bearing 2C210E ULAs. I tested them with my oscilloscope. I saw these familiar beautiful back porch (stairway) waves on the O'scope's screen.

As for the video transistor amplifier buffer circuit, I followed 1024MAK's to its components. However, 1024MAK is on the Europan side of the Atlanta Ocean while I am on the American side of the Atlanta Ocean. I put a transistor's equivalent on an artwork. The circuit design is basically the same as with stripboard as its support.

viewtopic.php?f=7&t=2405&hilit=video+buffer

Cheers,
DesSony

[BarryN]

No, You leave the ULA chip alone. You are fine now! There are 3 versions of ULA. The first two ULAs are buggy because they don't have their back porches feature yet. The final version [2C210E] had its back porch feature. 1024MAK has his better explanation on these ULAs' details somewhere on this forum. I bet that 1024MAK will concur on this one! Better forget about the 555 zigg.net mod. I have a few TS1000s bearing 2C210E ULAs. I tested them with my oscilloscope. I saw these familiar beautiful back porch (stairway) waves on the O'scope's screen.

As for the video transistor amplifier buffer circuit, I followed 1024MAK's to its components. However, 1024MAK is on the Europan side of the Atlanta Ocean while I am on the American side of the Atlanta Ocean. I put a transistor's equivalent on an artwork. The circuit design is basically the same as with stripboard as its support.

viewtopic.php?f=7&t=2405&hilit=video+buffer

Cheers,
DesSony

Agreed. I also have the 210E version ULA and it outputs a fine video signal with a back porch pulse. No 555 required. All you need to get a good composite video signal is a simple transistor amplifier. The circuit mentioned at the end of the previous post should do just fine.

[Dukes909]

No, You leave the ULA chip alone. You are fine now! There are 3 versions of ULA. The first two ULAs are buggy because they don't have their back porches feature yet. The final version [2C210E] had its back porch feature. 1024MAK has his better explanation on these ULAs' details somewhere on this forum. I bet that 1024MAK will concur on this one! Better forget about the 555 zigg.net mod. I have a few TS1000s bearing 2C210E ULAs. I tested them with my oscilloscope. I saw these familiar beautiful back porch (stairway) waves on the O'scope's screen.

As for the video transistor amplifier buffer circuit, I followed 1024MAK's to its components. However, 1024MAK is on the Europan side of the Atlanta Ocean while I am on the American side of the Atlanta Ocean. I put a transistor's equivalent on an artwork. The circuit design is basically the same as with stripboard as its support.

viewtopic.php?f=7&t=2405&hilit=video+buffer

Cheers,
DesSony

Excellent, thank you.

[Dukes909]

Agreed. I also have the 210E version ULA and it outputs a fine video signal with a back porch pulse. No 555 required. All you need to get a good composite video signal is a simple transistor amplifier. The circuit mentioned at the end of the previous post should do just fine.

So the 210E version is the only one I can get away with the transistor amplifier? I will get the transistor ordered tomorrow, if I can find it anywhere . I think I have the rest of the components already. I look forward to 1024MAK's reply about the ULA differences if he can point me to them. I have a few other ZX81's and T-1000's I will convert when I know which mod for which ULA.
Cheers everyone
Dukester

[dessony]

Great! And don't forget the stripboard, too!

DesSony