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Which video mod for composite?
Posted: Fri Oct 01, 2021 10:35 pm
by 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
Re: Which video mod for composite?
Posted: Fri Oct 01, 2021 11:34 pm
by 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
Re: Which video mod for composite?
Posted: Sat Oct 02, 2021 12:03 am
by Dukes909
Re: Which video mod for composite?
Posted: Sat Oct 02, 2021 12:17 am
by 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
Re: Which video mod for composite?
Posted: Sat Oct 02, 2021 12:26 am
by 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
Re: Which video mod for composite?
Posted: Sat Oct 02, 2021 1:28 am
by 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
Re: Which video mod for composite?
Posted: Sat Oct 02, 2021 1:40 am
by BarryN
dessony wrote: ↑Sat Oct 02, 2021 1:28 am
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.
Re: Which video mod for composite?
Posted: Sat Oct 02, 2021 1:48 am
by Dukes909
dessony wrote: ↑Sat Oct 02, 2021 1:28 am
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.
Re: Which video mod for composite?
Posted: Sat Oct 02, 2021 1:51 am
by Dukes909
BarryN wrote: ↑Sat Oct 02, 2021 1:40 am
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
Re: Which video mod for composite?
Posted: Sat Oct 02, 2021 2:05 am
by dessony
Great! And don't forget the stripboard, too!
DesSony