exxos's Atari, Amiga & retro forum

I think the RF shunt circuit is needed in addition to the composite mod and not sure removal of the RF modulator without adding the RF-shunt will work. My understanding is that it sits between the video, +12v, audio, channel(?) inputs for the RF mod and provides the video, +5v for the composite mod. I found a link to schematics and why the shunt is needed. Seems like a simple circuit to make.

Schematics: https://forums.atariage.com/topic/21271 ... x-removal/
Shunt is needed (4th comment): https://forums.atariage.com/topic/37484 ... -system-3/

raspberrypioneer wrote: 26 Jun 2025 09:37 I think the RF shunt circuit is needed in addition to the composite mod and not sure removal of the RF modulator without adding the RF-shunt will work. My understanding is that it sits between the video, +12v, audio, channel(?) inputs for the RF mod and provides the video, +5v for the composite mod. I found a link to schematics and why the shunt is needed. Seems like a simple circuit to make.

I disconnected my modulator and the comp mod continues to work, however I still have the PAL/SECAM switching. I did not need a shunt so it may be that the mod I have has it built in.

My modulator is still on the board, but all the inputs have been removed, and mine didn't have a 12v feed to it, only 5v.

raspberrypioneer wrote: 26 Jun 2025 09:37 Schematics: https://forums.atariage.com/topic/21271 ... x-removal/
Shunt is needed (4th comment): https://forums.atariage.com/topic/37484 ... -system-3/

I found those schematics last night, but for whatever reason, mine just works with the modulator disconnected. I think my PAL board is the source of my issues TBH, as just touching stuff on it makes it have a hissy fit.

Watching that video you posted, I think it was an Intellivision 2 or 3, so mot sure how similar they are.

Hmmm, with a lot of the online information being for NTSC machines I don't know how much applies in our case especially with the Radofin boards.

I've messaged the video author to see if this advances things. I've also messaged the World of Jani - his composite mod post with TFW8B device is March this year too. I think his setup is PAL - I spotted the PAL crystal I thought might be leaking on one of his boards :lol:. I'm hoping he'll respond and include screenshots of the output. If that looks good then I'll go for that option and with the cap replacements be able to catchup with something closer to your setup. Maybe that will shed light on things, though it sounds like the PAL board could be where the trouble lies.

On the 12v / 5v video input, I couldn't tell where you were picking up the 5v for your video mod from the pictures yesterday, sounds like its the 5v to the RF mod (ours isn't 12v input)?

raspberrypioneer wrote: 26 Jun 2025 12:36 Hmmm, with a lot of the online information being for NTSC machines I don't know how much applies in our case especially with the Radofin boards.

I wonder too. My comp mod board was from Italy and they use PAL, so maybe it is designed for that?

raspberrypioneer wrote: 26 Jun 2025 12:36 I've messaged the video author to see if this advances things. I've also messaged the World of Jani - his composite mod post with TFW8B device is March this year too. I think his setup is PAL - I spotted the PAL crystal I thought might be leaking on one of his boards :lol:. I'm hoping he'll respond and include screenshots of the output. If that looks good then I'll go for that option and with the cap replacements be able to catchup with something closer to your setup. Maybe that will shed light on things, though it sounds like the PAL board could be where the trouble lies.

On the 12v / 5v video input, I couldn't tell where you were picking up the 5v for your video mod from the pictures yesterday, sounds like its the 5v to the RF mod (ours isn't 12v input)?

I take the 5v from the mainboard, here:


And here for GND:


Both of which go straight under the mainboard to the bottom of the case where the comp board is.

But, it seems like I've been chasing my tail somewhat, I changed from my workbench display to the TV I would usually use and the flipping from PAL to Secam has stopped and I have a strong PAL signal and it all looks good now:


The current status is:

1. Recapping done throughout.
2. 5v and 12v regulators swapped for new.
3. Power ribbon replaced as it was falling to bits.
4. Modulator fully disconnected, but not removed.
5. Comp mod installed, but no shunt.

The image gets a little fuzzy when it's brighter, however I feel the image is more than acceptable. It seems that despite using lots of PAL devices on my workbench display, it doesn't like the composite out of the Intellivision. The display autodetects PAL, SECAM and NTSC over composite and I've not had issues like this before. My Colecovison has fantastic PAL composite on my workbench display.

I'm still not convinced the PAL board is 100%, I did find some corrosion on the bottom, so that's cleared up now too.

Bear in mind this is coming into my Retrotink and coming out as HDMI. There seems to be a bit of noise, but the image quality is acceptable to me, but I need to tweak the brightness to make it look a bit better.

Thanks for the 5v, GND info. I'll probably end up doing the same thing.

rubber_jonnie wrote: 26 Jun 2025 13:55 But, it seems like I've been chasing my tail somewhat, I changed from my workbench display to the TV I would usually use and the flipping from PAL to Secam has stopped and I have a strong PAL signal and it all looks good now:

Wow that looks great! I hope I end up with something like that! I don't have anything like the Retrotink device but this Samsung TV I use works well for the various retro's I've got (not a patch on the impressive collection you've got - more collecting needed by me obviously :lol:)

rubber_jonnie wrote: 26 Jun 2025 13:55 The current status is:

1. Recapping done throughout.
2. 5v and 12v regulators swapped for new.
3. Power ribbon replaced as it was falling to bits.
4. Modulator fully disconnected, but not removed.
5. Comp mod installed, but no shunt.

The image gets a little fuzzy when it's brighter, however I feel the image is more than acceptable. It seems that despite using lots of PAL devices on my workbench display, it doesn't like the composite out of the Intellivision. The display autodetects PAL, SECAM and NTSC over composite and I've not had issues like this before. My Colecovison has fantastic PAL composite on my workbench display.

I'm still not convinced the PAL board is 100%, I did find some corrosion on the bottom, so that's cleared up now too.

Thanks for the status. I'll mostly follow a similar path, the ribbon cable and PAL board look in good condition so hopefully will not have anything special to do there. Not sure yet which video mod I will go for but good to know the one you have works (which sounds like the 'classic' Intellivision composite mod - https://wiki.intellivision.us/index.php ... dification) and no need for the RF-shunt. I'm hoping for news about TFW8B deluxe device first, it could be ideal assuming the video quality is good.

raspberrypioneer wrote: 26 Jun 2025 14:41 Thanks for the 5v, GND info. I'll probably end up doing the same thing.

No worries :)

raspberrypioneer wrote: 26 Jun 2025 14:41 Wow that looks great! I hope I end up with something like that! I don't have anything like the Retrotink device but this Samsung TV I use works well for the various retro's I've got (not a patch on the impressive collection you've got - more collecting needed by me obviously :lol:)

I've lost track of how many systems I have, I count myself lucky, you can see some here:


You can never have enough, get collecting :) Please excuse the current untidiness!

raspberrypioneer wrote: 26 Jun 2025 14:41 Thanks for the status. I'll mostly follow a similar path, the ribbon cable and PAL board look in good condition so hopefully will not have anything special to do there. Not sure yet which video mod I will go for but good to know the one you have works (which sounds like the 'classic' Intellivision composite mod - https://wiki.intellivision.us/index.php ... dification) and no need for the RF-shunt. I'm hoping for news about TFW8B deluxe device first, it could be ideal assuming the video quality is good.

No problem.

My ribbon cable was just disintegrating, and the 'wires' were in danger of touching. Not going to happen now. I do have the PAL IC coming so may swap it later on, but so far it's looking good. I tweaked the brightness a little and it looks better still. I'm sure you'll figure out which video mod to go for and It'll be interesting to see how you get on.

The schematic you shared is almost identical to my comp board, which is good to know. The boards I've had from TFW8bit are great quality and work perfectly for my 2600 & 7800 but they are only a single transistor composite mod and don't match that schematic, so may not be suitable for the Intellivision.

The standard single transistor comp mod that I've used a lot looks like this:


Not even close to the Intellivision one you linked to. IIRC this is what TFW8bit boards are like, just using smaller surface mount parts. Does make me wonder if mine has a built in shunt.

rubber_jonnie wrote: 26 Jun 2025 15:38 You can never have enough, get collecting :) Please excuse the current untidiness!

Love it. I'll show the other half so she knows what I'm aiming for! :lol:

rubber_jonnie wrote: 26 Jun 2025 15:38 The schematic you shared is almost identical to my comp board, which is good to know. The boards I've had from TFW8bit are great quality and work perfectly for my 2600 & 7800 but they are only a single transistor composite mod and don't match that schematic, so may not be suitable for the Intellivision.

Yeah, it seems too simple. I wonder what the video quality is like assuming it does work ok. Anyway I'll hopefully get a response back to the messages I've left for TFW8B and World of Jani. They're both credible sources so a bit puzzling. Either way will certainly let you know where I go with this, will probably be the mod you went for. :lol:

raspberrypioneer wrote: 26 Jun 2025 16:54 Love it. I'll show the other half so she knows what I'm aiming for! :lol:

Aim high :)

raspberrypioneer wrote: 26 Jun 2025 16:54 Yeah, it seems too simple. I wonder what the video quality is like assuming it does work ok. Anyway I'll hopefully get a response back to the messages I've left for TFW8B and World of Jani. They're both credible sources so a bit puzzling. Either way will certainly let you know where I go with this, will probably be the mod you went for. :lol:

Based on everything I've seen so far since we started discussing this, its too simple IMHO. I've built a few on protoboard of the single transistor type, you could easily build one to see how it fares.

I heard back from Jani, who mentioned that the TFW8B mod gives a decent quality picture for the two Intellivisions he has, but that there may be better composite solutions out there. He mentioned that some people get a black screen with the RF-modulator removed. He had no need to install the RF-shunt though.

Considering we have the same motherboard type, I think I'd be best to get the Winmar mod you have or one with SMD components from eurowifi but essentially the same mod I think. If I need the RF-shunt I could probably make that circuit, hopefully won't need to as you found.

I might go for the TRRS port and cable approach as I like the single port for composite. Will possibly remove the RF modulator altogether to use the hole for the TRRS port, but that needs some thought because the TRRS port connection needs to be secure and the existing hole for RF is pretty big. It could look quite tidy if done right I hope!

raspberrypioneer wrote: 26 Jun 2025 22:28 I heard back from Jani, who mentioned that the TFW8B mod gives a decent quality picture for the two Intellivisions he has, but that there may be better composite solutions out there. He mentioned that some people get a black screen with the RF-modulator removed. He had no need to install the RF-shunt though.

Sorry I missed your post yesterday, it was our wedding anniversary so we were out all day. That info kind of ties in with what we've seen I think, the single transistor comp mods are good but not always best for some circumstances.

raspberrypioneer wrote: 26 Jun 2025 22:28 Considering we have the same motherboard type, I think I'd be best to get the Winmar mod you have or one with SMD components from eurowifi but essentially the same mod I think. If I need the RF-shunt I could probably make that circuit, hopefully won't need to as you found.

Sounds like a plan. I doubt the shunt circuit would take much to build, there isn't a lot to it, and I think now my Winmar mod is working pretty well for sure.

Aside from the electrolytic caps, the Winmar mod is all SMD, and there it a ton of space in the case so no issues there.

raspberrypioneer wrote: 26 Jun 2025 22:28 I might go for the TRRS port and cable approach as I like the single port for composite. Will possibly remove the RF modulator altogether to use the hole for the TRRS port, but that needs some thought because the TRRS port connection needs to be secure and the existing hole for RF is pretty big. It could look quite tidy if done right I hope!

Yeah, the TRRS ports are very good for this sort of thing, and look great on my 2600 and 7800, I just added cables on my Intellivision because I wanted it to be reversible, so no case mods, and the hole for the modulator is pretty big, I did a similar thing on my Coleco and Tandy Coco too.