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adam1977

Jittery Screen

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I'm trying to fix my ColecoVision, i've already sorted a power supply but now there's a problem where the screen looks jittery, it looks as though everything is just moving up and down very slightly :?

 

I've made a short video, but it doesn't look half as bad when viewed online? maybe that's a clue as to what's wrong with it?

 

Any help will be greatly appreciated :twisted:

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Mine does this too. The picture gets better and more stable after the system has been on a few minutes. I guess it needs to warm up. Like my old Dodge😉

Mine had noise in the audio too, believe it or not removing the lid on the rf modulator fixed that. 

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Thanks for the reply, i'll leave it powered on for a while then and see if that helps :twisted:

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6 hours ago, Charlie_ said:

Mine does this too. The picture gets better and more stable after the system has been on a few minutes. I guess it needs to warm up. Like my old Dodge😉

Mine had noise in the audio too, believe it or not removing the lid on the rf modulator fixed that. 

Probably needs to adjust the audio tuner.  Removing the lid changed the frequency of the audio modulator, apparently for the better.

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Is your CV AV modded at all? Not that it matters, but the jittering you are talking about...based on your video, I'm wondering if your TV is doing this trying to figure out the interlaced signal coming from the CV?

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1 hour ago, -^CrossBow^- said:

Is your CV AV modded at all? Not that it matters, but the jittering you are talking about...based on your video, I'm wondering if your TV is doing this trying to figure out the interlaced signal coming from the CV?

 

It's not AV modded, just the standard RF cable output, but I have thought about modding it to get rid of this problem.

 

2 hours ago, ChildOfCv said:

Probably needs to adjust the audio tuner.  Removing the lid changed the frequency of the audio modulator, apparently for the better.

 

I'll have a look at that, any idea which pots to adjust?

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It is possible that getting it AV modded could correct the issue. I know that the entire reason I AV modded my Intellivision was because it was doing the jumping bean dance through RF on my flat panel in the game room. Adding composite to it took care of the issue. In fact, every single Intelly that I've hooked up via RF to that TV screen jumps the entire time and really bugs me to no end. Having said that, I have two CVs. One composite AV modded and the other is nearly stock. Neither one caused any jitteriness like this. The one I AV modded I did so because the RF on it was horrible no matter how much I adjusted it. The other one actually has a really nice RF picture from it and I leave it as is for now.

 

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1 hour ago, adam1977 said:

 

It's not AV modded, just the standard RF cable output, but I have thought about modding it to get rid of this problem.

 

 

I'll have a look at that, any idea which pots to adjust?

The one in the corner of the RF box is audio, and the one in the middle is the main channel adjust.  If your picture looks great, then the main channel output is probably okay.

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17 hours ago, adam1977 said:

I've come across this Ben Heck AV mod, does anyone know if it would be ok for my PAL ColecoVision?

The transistor is said to get hot, and it also places a load on the video circuit that makes it less than ideal.  I think there is a better solution out there that's based on an op-amp.

 

Yeah, here it is.

 

https://store.retrofixes.com/products/colecovision-composite-upgrade-kit

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13 hours ago, adam1977 said:

Many thanks for the link, shame it's NTSC only though :(

 

However i've come across this on eBay, happy days :D

I think I'd go for this one instead:  https://www.ebay.co.uk/itm/ColecoVision-A-V-Composite-Video-Mod-Kit-NTSC-PAL-LM318/312816022264?_trkparms=aid%3D1110001%26algo%3DSPLICE.SIM%26ao%3D2%26asc%3D40733%26meid%3Dcdc4f9fc7235426381b9be3d51a1613d%26pid%3D100623%26rk%3D2%26rkt%3D6%26sd%3D182205220905%26itm%3D312816022264%26pmt%3D0%26noa%3D1%26pg%3D2047675&_trksid=p2047675.c100623.m-1

 

The only difference between NTSC and PAL is color subcarrier frequency and its phase shift between lines.  But none of that matters at final amplification, so you really can use the same circuit either way.

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Thanks a lot for the link, i'll contact them and see if they'll post to England :twisted: 

 

I did try and buy the kit from the seller in Turkey, but each time I do my payment gets cancelled... i've contacted him but he hasn't responded.

 

Thanks again.

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