Intellivision Board details

[rubber_jonnie]

Having sold @raspberrypioneer one of my Intellivision Pirto II carts, we've been discussing revisions of boards and a little about Radofin, who also made the Aquarius for Mattel.

Since I didn't seem to do much documentation for my own Intellivision, I thought I'd pop it apart and snag some pics to add to the collective intelligence.

This is the mainboard:

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And this is the model, manufactured by Radofin:

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The power board showing the awful ribbon cable:

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The video board:

IMG20250625084410.jpg (336.56 KiB) Viewed 172 times

I'm not sure calling it a video board is 100% correct, however it uses a TBA520 IC, which is used for PAL, so I think it is rather a video output board feeding the modulator rather than generating the graphics, which is done on the mainboard.

And last, but by no means least, the composite adapter board.

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The composite adapter board has 4 connections, 5v, GND, video in (red cable) and audio in (white cable) the are simply picked off the modulator inputs like so:

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I used shielded cable to hook up the adapter, and was able to feed the output cables from the composite board out through the modulator hole in the case, so no cutting needed. There are no parts that need to be removed either.

The machine doesn't have many electrolytic caps. I've replaced the caps on the PAL video board and the PSU. I also replaced the 7805 with a Traco. There are a couple on the mainboard that I may replace, but I'm not convinced it will give me any improvement to the video signal.

Any questions please shout.

[raspberrypioneer]

Thanks for the pics, they help a lot.

I have the same Radofin 'clone' board type. It isn't enclosed by the metal shield panels which I've seen on many YouTube videos which is a blessing as they look a nuisance to take off. I guess those types were more for the US market.

IMG_20250624_115639740.jpg (235.03 KiB) Viewed 158 times

My video board looks ok, but the lime-green component (not sure what it is), looks odd. Not sure if I'm seeing a leak or split glue. The video board has a bit of a homemade feel to it! I guess that's cheap late 70s, early 80s tech!

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I think I've got to get the caps replaced next as they're so old and have probably deteriorated. I think I'll just do all of them, probably head over to eBay for that. The video on my console seems to be the main problem. It's RF just now but I have found that video doesn't always appear on powering on (although fine this morning), I need to fine-tune a few times until the machine settles down over 20 minutes or so. There is a bit of tearing on the top line of the screen (most noticeable on the pitro2 menu) which I can generally fine-tune out. After settling down, the RF video quality is reasonably good, although I'll definitely be looking at the video mod options.

The caps I have are these:
Main board: 4 x 10uF 25v, 1 x 1uF 50v
Video board: 1 x 10uF 16v
Power board: 3 x 100uF 16v, 1 x 2200uf 25v and the big beast 10000uF 16v!

I think I'll replace those, then see how it looks before moving onto the video mod. Perhaps the voltage regulator should be replaced while I'm at it.

[rubber_jonnie]

Thanks for the pics, they help a lot.

I have the same Radofin 'clone' board type. It isn't enclosed by the metal shield panels which I've seen on many YouTube videos which is a blessing as they look a nuisance to take off. I guess those types were more for the US market.

Mine wasn't shielded either, probably cost reduction since it wasn't required in the UK. My ColecoVision on the other hand had shields on it and they were a pain.

My video board looks ok, but the lime-green component (not sure what it is), looks odd. Not sure if I'm seeing a leak or split glue. The video board has a bit of a homemade feel to it! I guess that's cheap late 70s, early 80s tech!

The lime green item is a PAL crystal, it's not leaking, that's glue to prevent it from coming loose, quite normal.

I think I've got to get the caps replaced next as they're so old and have probably deteriorated. I think I'll just do all of them, probably head over to eBay for that. The video on my console seems to be the main problem. It's RF just now but I have found that video doesn't always appear on powering on (although fine this morning), I need to fine-tune a few times until the machine settles down over 20 minutes or so. There is a bit of tearing on the top line of the screen (most noticeable on the pitro2 menu) which I can generally fine-tune out. After settling down, the RF video quality is reasonably good, although I'll definitely be looking at the video mod options.

The caps I have are these:
Main board: 4 x 10uF 25v, 1 x 1uF 50v
Video board: 1 x 10uF 16v
Power board: 3 x 100uF 16v, 1 x 2200uf 25v and the big beast 10000uF 16v!

I think I'll replace those, then see how it looks before moving onto the video mod. Perhaps the voltage regulator should be replaced while I'm at it.

Video on mine is still an issue, tearing too even on composite, flipping between PAL & SECAM, hence why I will take a look at the PAL board.

I replaced the last of my caps on the mainboard this morning. Whilst they all tested OK for capacitance, every last one had high ESR, so I'm happy to have replaced them. TBH if you don't have a Traco to hand, I'd say just replace the 7805 like for like. There is also a 7812 12v regulator, I may also replace that, and I've ordered a replacement TBA520 in case mine is unhappy. If I can figure out the reason for the poor video (I think it's that board TBH) I'll post on here.

Be aware the grey capacitor, bottom left on my mainboard, is Bi-Polar, however the underside of the board is marked with a '+' so it can be replaced with a normal polarised cap.

[raspberrypioneer]

The lime green item is a PAL crystal, it's not leaking, that's glue to prevent it from coming loose, quite normal.

Thanks, I thought was more likely that, there's a fair bit of glue sprinkled around the boards!

I replaced the last of my caps on the mainboard this morning. Whilst they all tested OK for capacitance, every last one had high ESR, so I'm happy to have replaced them. TBH if you don't have a Traco to hand, I'd say just replace the 7805 like for like. There is also a 7812 12v regulator, I may also replace that, and I've ordered a replacement TBA520 in case mine is unhappy. If I can figure out the reason for the poor video (I think it's that board TBH) I'll post on here.

Ok good to know, yes I'll probably replace it too.

Be aware the grey capacitor, bottom left on my mainboard, is Bi-Polar, however the underside of the board is marked with a '+' so it can be replaced with a normal polarised cap.

Right! Wasn't aware of that - its the 1uF 50v cap on mine at the looks of it.

On the video mod then I found this so far.

From the AtariAge forum with recent posts https://forums.atariage.com/topic/36971 ... o-out-mods (has screenshots there), it looks like composite video quality can be improved with the RF modulator removed and it appears it has to be replaced with an 'RF-shunt', which sounds like a board to take care of the 12v input in some way. I'm trying to understand more there but so far the 'best' option seems to be OGHugo composite mod (RF Module Remove - Shunt Built In), available on eBay but £££ with delivery https://www.ebay.co.uk/itm/126608617925.

I found a clean looking mod online from this link using a TFW8B deluxe composite mod board: https://blog.worldofjani.com/?p=8499 but there isn't much detail and I wouldn't go down that route without more info. The solution to provide composite from the single port replacing the RF one looked good though. This would mean a port and cable as shown in this link https://www.retrofixes.com/products/trr ... site-cable (TRRS 3.5mm to RCA Cable and Port).

Merging the OGHugo composite option with the tidy TRRS option I think would look good and no case modification would be needed (I'm generally not keen on that). Securing the TRRS port fitting on the console might need attention though.

[rubber_jonnie]

Right! Wasn't aware of that - its the 1uF 50v cap on mine at the looks of it.

If yours is bi-polar then it will have BP written on it like mine.

On the video mod then I found this so far.

From the AtariAge forum with recent posts https://forums.atariage.com/topic/36971 ... o-out-mods (has screenshots there), it looks like composite video quality can be improved with the RF modulator removed and it appears it has to be replaced with an 'RF-shunt', which sounds like a board to take care of the 12v input in some way. I'm trying to understand more there but so far the 'best' option seems to be OGHugo composite mod (RF Module Remove - Shunt Built In), available on eBay but £££ with delivery https://www.ebay.co.uk/itm/126608617925.

I found a clean looking mod online from this link using a TFW8B deluxe composite mod board: https://blog.worldofjani.com/?p=8499 but there isn't much detail and I wouldn't go down that route without more info. The solution to provide composite from the single port replacing the RF one looked good though. This would mean a port and cable as shown in this link https://www.retrofixes.com/products/trr ... site-cable (TRRS 3.5mm to RCA Cable and Port).

Merging the OGHugo composite option with the tidy TRRS option I think would look good and no case modification would be needed (I'm generally not keen on that). Securing the TRRS port fitting on the console might need attention though.

Thanks I'll take a look at those. Thus far, finding a schematic of the PAL board has not been successful. I get the feeling that NTSC machines didn't have an equivalent, but I'd be happy to be wrong. General schematics for the mainboard are available.

Of interest is that the TBA520 runs off 12v, so I am going to have a look and see how power looks for that, I may drop a new 7812 in. There are also inputs on pins 14 &15 that 'seem' to suggest some control in turning PAL on and off, so I will check that out too.

Just to add, one on eBay looks like a version of the one I have, and I have used the THW8Bit upgrade in one or two 2600's and it works just fine. Also the one that is used on looks like a later model based on the switch that is near the modulator. Either that or it's a channel switch for an NTSC machine. I may try removing/disconnecting my modulator.

[rubber_jonnie]

OK, so next to the crystal, is a small variable capacitor, pressing on it caused on screen variations, so I marked its position and adjusted it several directions and then back again, and it has made a difference. I haven't looked at the other 2 variable resistors but I think they are for voltage references, but I may hit them with some contact cleaner and a wiggle, but I will also mark the positions beforehand.

I'll disconnect the modulator later.

[raspberrypioneer]

Thanks I'll take a look at those. Thus far, finding a schematic of the PAL board has not been successful. I get the feeling that NTSC machines didn't have an equivalent, but I'd be happy to be wrong. General schematics for the mainboard are available.

I've looked at a number of YouTube videos mostly to consider video mods, and not seen this extra board so far, probably because they're from US youtubers with NTSC and original / non-clone boards. Not sure what Euro Intellivisions were like. I guess some had something special for SECAM. I'll be on YT a bit more for this so will let you know if anything useful crops up.

Of interest is that the TBA520 runs off 12v, so I am going to have a look and see how power looks for that, I may drop a new 7812 in. There are also inputs on pins 14 &15 that 'seem' to suggest some control in turning PAL on and off, so I will check that out too.

I'll replace both regulators I think for what they are. Will probably just get this and the caps from Retroleum I've used before - looks like they have all the immediate bits I need.

Just to add, one on eBay looks like a version of the one I have, and I have used the THW8Bit upgrade in one or two 2600's and it works just fine. Also the one that is used on looks like a later model based on the switch that is near the modulator. Either that or it's a channel switch for an NTSC machine. I may try removing/disconnecting my modulator.

I saw they were advertised for the 2600 particularly among others, but TFW8B don't mention the Intellivision though - I've messaged them to find out more, they might know. If it does work the video quality is unknown at this stage. The other options out there look more complicated so feels unlikely will be the right solution in this case I think.

OK, so next to the crystal, is a small variable capacitor, pressing on it caused on screen variations, so I marked its position and adjusted it several directions and then back again, and it has made a difference. I haven't looked at the other 2 variable resistors but I think they are for voltage references, but I may hit them with some contact cleaner and a wiggle, but I will also mark the positions beforehand.

I'll disconnect the modulator later.

Sounds like progress is being made, hopefully will get to the bottom of it. At least we have the same Radofin boards to compare with.

[rubber_jonnie]

I've looked at a number of YouTube videos mostly to consider video mods, and not seen this extra board so far, probably because they're from US youtubers with NTSC and original / non-clone boards. Not sure what Euro Intellivisions were like. I guess some had something special for SECAM. I'll be on YT a bit more for this so will let you know if anything useful crops up.

Yeah, the US versions seem to have shields and no encoder board, not even NTSC, plus they have a channel switch as I thought.

I'll replace both regulators I think for what they are. Will probably just get this and the caps from Retroleum I've used before - looks like they have all the immediate bits I need.

Yeah, they are easy to swap out and cheap, so worth doing.

I saw they were advertised for the 2600 particularly among others, but TFW8B don't mention the Intellivision though - I've messaged them to find out more, they might know. If it does work the video quality is unknown at this stage. The other options out there look more complicated so feels unlikely will be the right solution in this case I think.

That board was a standard one that TFW8bit have sold for a while, I also have one in my 7800, works well there too. It's a simple amplifier so should work in most scenarios, but doesn't include audio without mods on the 2600 and 7800 IIRC.

Sounds like progress is being made, hopefully will get to the bottom of it. At least we have the same Radofin boards to compare with.

Hopefully, I actually had a had a half decent image out of it earlier, a bit over saturated, but nothing that tweaking the picture couldn't solve. I think the PAL board may be a part of the issue, I'll see if any of the ICs are running hot. I did try freeze spray earlier and it didn't help, but some of the IC's look pretty old so may be marginal and they are all simple 74LS logic IC's.

I've yet to disconnect the modulator.

[raspberrypioneer]

I've yet to disconnect the modulator.

I found this recent YT video: - shows various options, not too long, with mods that are available now. Looks like removal of the RF modulator makes a huge difference. The recommended board is from the US and gets a bit pricey considering the delivery cost. The author has made a board which very similar (I prefer it), perhaps he'll be willing to share the schematics.

[rubber_jonnie]

Looks like removal of the RF modulator makes a huge difference.

It certainly seems to be better without the modulator.

The shunt is perplexing as it isn't clear from the video wether it's needed or not, so more digging required, but I can disconnect and see what I get, my composite adapter looks similar to this: Composite mod

Too late to muck around tonight, will have a look tomorrow.

EDIT: I tried to compare the circuit above with the circuit on that web page. I can't quite read the values for some components on mine, but tracing what I can see, I'd say it's a carbon copy of the circuit in that link.