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Intellivision II AV Mod Lots of Interference

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Hi guys. I just modded an INTV II using the very common schematic available on the intellivision wiki.

 

http://wiki.intellivision.us/index.php?title=Intellivision_Composite_Video_Modification

 

The mod works, but there is a ton of interference. On the INTV startup screen there is tons of movement over the greens. Two things I differed from this mod, I used a 680 Ohm resistor instead of the 660 Ohm, also I only used hookup wire no coax. I suppose the coax could make a difference, but this is a lot of intereference.

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Hi guys. I just modded an INTV II using the very common schematic available on the intellivision wiki.

 

http://wiki.intelliv...eo_Modification

 

The mod works, but there is a ton of interference. On the INTV startup screen there is tons of movement over the greens. Two things I differed from this mod, I used a 680 Ohm resistor instead of the 660 Ohm, also I only used hookup wire no coax. I suppose the coax could make a difference, but this is a lot of intereference.

ok a couple things. did you keep rf box attached? cause you should. second if you used standard wire instead of coax you need to twist the 2 wires to bring down interferance? third use 10uf caps not 100uf like it says(could be problem) and 680 ohm is ok. also pictures would really help. Edited by pimpmaul69

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When you get this worked out, you should go into a mod service for INTV. There is nobody performing this mod, as there is for Atari 2600.

i have stated several times i repair video game consoles and would do av mods, led mod, and system changer mod for original systems.

 

i am probably going to start modifying original consoles to have a pin connector to plug intv ii controllers into an intv iii or original console sometime soon.

i also mod atari 2600's and colecovisions and several others.

Edited by pimpmaul69
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If I'm interpreting your description, you're seeing what appears to be an almost conveyor belt-like pattern in the center 2/3rd square of the screen. Going from memory, a couple things that help w/ the Inty 2

 

1: Tap your video/audio directly at the modulator

2: Add a bypass cap across the +5 / GND on your circuit. 1000-2200uf should be adequate.

3: Hookup wire is fine. Shielded might buy you some gain in quality but I've had no problem with hookup wire. Just move your wires & circuit around while it's on and you'll know instantly if they're picking up interference or if it's coming from the video source or due to unclean power.

 

I can't remember which chips are the noisy ones, but adding more bypass caps across the chips can help too. Inty 2 units are definitely noisier for A/V mods than other versions.

Edited by FABombjoy

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Here is a picture of the issue. Some of the noise you see is camera induced. Conveyor belt pattern does seem to be appropriate, but its on the entire screen. It shows up on green the worst.

 

I have not yet been able to try the remedies suggested in this thread. I have some Belden Coax coming in the mail tomorrow, that is high quality stuff for making Audiophile grade AV cables, so if the its due to my use of hookup wire, this stuff should clear up any issues whatsoever. After that I will try some of the other remedies mentioned, unless from my picture that gives anybody else other ideas.

post-30505-0-34019900-1330483361_thumb.jpg

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Here is a picture of the issue. Some of the noise you see is camera induced. Conveyor belt pattern does seem to be appropriate, but its on the entire screen. It shows up on green the worst.

 

I have not yet been able to try the remedies suggested in this thread. I have some Belden Coax coming in the mail tomorrow, that is high quality stuff for making Audiophile grade AV cables, so if the its due to my use of hookup wire, this stuff should clear up any issues whatsoever. After that I will try some of the other remedies mentioned, unless from my picture that gives anybody else other ideas.

you are not using the rf / rca cable that you use originally are you. if so dont. plug in standard rca.

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No, I'm using a regular Composite cable, I do not have the RF connected to the TV. The RF modulator is still connected to the system though.

remove the rf cableif it is hooked up t system. that also causes interferance if it is hooked up to system. i also agree to use a 1000uf or 1500uf cap.(those 2 sizes are the easy ones to get) Edited by pimpmaul69

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Hi guys. I just modded an INTV II using the very common schematic available on the intellivision wiki.

 

http://wiki.intelliv...eo_Modification

 

The mod works, but there is a ton of interference. On the INTV startup screen there is tons of movement over the greens. Two things I differed from this mod, I used a 680 Ohm resistor instead of the 660 Ohm, also I only used hookup wire no coax. I suppose the coax could make a difference, but this is a lot of intereference.

ok a couple things. did you keep rf box attached? cause you should. second if you used standard wire instead of coax you need to twist the 2 wires to bring down interferance? third use 10uf caps not 100uf like it says(could be problem) and 680 ohm is ok. also pictures would really help.

 

Not to derail the thread, but I took the RF box out of my INTV II. Why should you keep the RF box attached? I put the unit aside because I was only getting audio and a black screen out of it.

Thanks,

Bob

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from many others who have done the mod, tons of them stopped working when they removed the rf unit, but workedwhen put back in. sseveral people threw out the rf box before verifying and have useless paperweights.

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Hello,

 

I happened to have to built the same intellivision composite video mod with small variations, basically the same circuitry. I tried some of the suggestions present in this thread, such as changing the capacitors across the circuit from 100uF to 10uF with little or no difference, also change the 22ohms resistor a 40 or 50 ohms values produced worse results (more color and contrast bleeding), found a compromise around 33 ohms for this resistor. On the introduction screen of many mattel intellivision games the distortion and bleeding is more noticeble than on the games action screen. On standard definition crt tvs I notice a small amount of trembling of the whole screen (although small it is bothersome) but the otherwise is fairly good, such effect was not noticed on a high definition lcd screen but the distortion and bleeding is more saliented there . As suggested I tried to cut off the video signal going to the RF modulator and when I did so there would be no video feed on the circuitry board, I heard that disconnecting the RF modulator altogether would get rid of such video distortions. The use of bypass capacitor in my case did not help much (using 1000uF connected to grd and 5V rails) Any suggestion would be appreciated.

 

6886737392_ac0f2b4cc2_n.jpg

 

 

 

Thanks,

tk3000

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I'm watching this thread with interest. :)

 

I HIGHLY recommend you get the console off the carpet while working on it. Carpet=static=bad for your unprotected electronics.

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I'm watching this thread with interest. :)

 

I HIGHLY recommend you get the console off the carpet while working on it. Carpet=static=bad for your unprotected electronics.

Thanks, I guess I know that. It was for photo purposes, so that I could spread everything and it all could be seen. Old electronics tend to be much more resilient though, in a modern circuit board with sms ICs and billions of transistor per IC is a different story and I would not touch them without grounding myself often or having an anti-static wrist strap and certainly laying them in an non-conductive surface (cardboard works well)

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Just as a side note, if anyone knows how to get the Intellivision II video mod working without the RF box, please PM me. It was a perfectly working unit before I modified it (and it still works, as I can get sound). :(

 

Thanks, Bob

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Just as a side note, if anyone knows how to get the Intellivision II video mod working without the RF box, please PM me. It was a perfectly working unit before I modified it (and it still works, as I can get sound). :(

 

Thanks, Bob

Maybe ask in the marketplace if someone has a busted Intv you can have cheap? Then pull the RF off of it.

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The reported fact that removing the RF modulator from an INTV II prevents the A/V mod from working caught my attention, so I dug into schematics. The video signal is created by a network of resistors connected to the AY-3-8915 and then travels through a diode (CR4) to the RF modulator. This diode MUST have DC current flowing through it, otherwise the video signal will be blocked. Studying the schematics reveals that the only possible source of this DC current is the RF modulator. Either disconnecting the video signal from the RF modulator or completely removing the RF modulator will thus remove this DC current, resulting in NO video signal to the A/V mod.

 

To get the video signal to the A/V mod in an INTV II without the RF modulator, a new source for this DC current must be created. One possibility is to copy the INTV I circuitry - add a 3.3Kohm resistor between the video signal and +5V (The INTV I actually has 2 resistors in series with a diode, but all that's needed for the INTV II is one resistor with a value of 3.3Kohms.).

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My Intellivision 1 through RF looks very good to me. I see no interference at all and it even looks better than a composite modded Atari that I have. Is there really any benefit to an AV mod for it?

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My Intellivision 1 through RF looks very good to me. I see no interference at all and it even looks better than a composite modded Atari that I have. Is there really any benefit to an AV mod for it?

If your Inty looks good, and you have a TV that supports the signal. Then no. Unless you want to look forward and mod it for future compatibility.

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The reported fact that removing the RF modulator from an INTV II prevents the A/V mod from working caught my attention, so I dug into schematics. The video signal is created by a network of resistors connected to the AY-3-8915 and then travels through a diode (CR4) to the RF modulator. This diode MUST have DC current flowing through it, otherwise the video signal will be blocked. Studying the schematics reveals that the only possible source of this DC current is the RF modulator. Either disconnecting the video signal from the RF modulator or completely removing the RF modulator will thus remove this DC current, resulting in NO video signal to the A/V mod.

 

To get the video signal to the A/V mod in an INTV II without the RF modulator, a new source for this DC current must be created. One possibility is to copy the INTV I circuitry - add a 3.3Kohm resistor between the video signal and +5V (The INTV I actually has 2 resistors in series with a diode, but all that's needed for the INTV II is one resistor with a value of 3.3Kohms.).

Thanks! I will give this a try when I get home :)

 

@SlowCoder and Rook3 - thank you for the ideas. If the above doesn't work, I will go down this avenue. :)

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:( Adding the 3.3K resistor didn't work. I double checked my wiring, and I still got the blank screen.

 

I'll try ordering the RF box.

 

Thanks anyway,

Bob

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