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alex_79

CD4050 A/V mod on PAL atari 2600

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Just wanted to share this since it's hard to find info on A/V mod for PAL vcs.

I used the schematic from Atariage FAQ (the CD4050 mod) on a PAL 2600jr and it works great! You only have to find where to pick the signals since the TIA pinout is different between PAL and NTSC. The junior (and 6 switch) already have the luma and sync signals buffered by a CD4050 chip, so the mod is a little simpler than on a 4-switch.

 

Here is a schematic of the circuit (exactly the same one on AA faq but without the CD4050, cause I used the one already installed on the console)

post-10599-1215111542_thumb.png

 

 

signals on the board:

post-10599-1215111650_thumb.jpg

Sync: R51, upper side (CD4050 pin 12)

Lum0: R52, upper side (CD4050 pin 2)

Lum1: R49, upper side (CD4050 pin 10)

Lum2: R53, upper side (CD4050 pin 15)

Color: R29, bottom side (TIA pin 9)

Audio: W2, upper side (TIA pin 13)

 

Power (+5v) and ground can be tapped into many different places on the board and are not indicated in the pic.

For example, power can be found at any point continuous with the right pin of the voltage regulator (with printed side facing you and pins pointing downwards), while ground at any point continuous with the center pin of the regulator or with the metal shield.

 

The pic refers to a PAL-B, rev. B board. I've seen some images of PAL-I (for UK market) junior boards and they have a slighty different layout, so you may need to change something. (use the schematics on AA as reference)

 

 

 

 

I removed resistors R49,R51,R52,R53 and R55 and cut the center pin of transistor Q3 and Q4. This should avoid interferences with the mod and reduce power load of the console but it's not necessary and, since I'm quite inexperienced in electronics, I'm not even sure this is the correct way to do it. :dunce: (Suggestion from electronics experts are welcome!)

 

 

I removed the rf connector and used the hole left in the case for the new scart cable that I soldered directly on the mod board. I also modified the channel select switch to select between composite or s-video (you need to cut some traces on the board and solder a couple of jumper to isolate the switch from the rf circuit). In this way I avoided to drill or modify the case in any way. Next time I plan to make the cable removable using a 6-pin mini din connector (like those used for PS-2 computer mouse and keyboard) with luma/composite, chroma, audio and ground signals.

post-10599-1215112106.jpg

The hole of the rf connector is the right size for mini-din, so this shouldn't require any case mod too. :)

 

 

post-10599-1215111800_thumb.jpgpost-10599-1215111810_thumb.jpg

 

post-10599-1215111833_thumb.jpgpost-10599-1215111846_thumb.jpg

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Edited by alex_79
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Hello!

 

What isn't quite clear for me (as an even more amateurish amateur :-)) is where exactly - in the schematic, not on the board, the latter is clear - you tapped the signals for color and sound (in contrast to the PAL schematics, the hand-drawn NTSC 4-switch schematic on this site doesn't show the part numbers, and the FAQ only refers to "top of C210/R210" and "bottom of R206/C208" here, just these part numbers don't exist in the Jr.). And, though is pretty obvious that you tapped TIA csyn on top of R51, TIA lum0 on top of R52, TIA lum1 on top of R49, I cannot find a pin labelled "lum2" on this site's PAL VCS Jr. schematics - you tapped the pin labelled "lum3" on top of R53 instead and this gives the same result?

 

I'd like to try this mod on a 6-switch NTSC console and thus cannot get color and audio from the same spots of the mainboard, that's why I'm asking: are there any resistors/capacitors/anything else between the TIA pins and the tapping points?

 

 

Thorsten

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What isn't quite clear for me (as an even more amateurish amateur :-)) is where exactly - in the schematic, not on the board, the latter is clear - you tapped the signals for color and sound (in contrast to the PAL schematics, the hand-drawn NTSC 4-switch schematic on this site doesn't show the part numbers, and the FAQ only refers to "top of C210/R210" and "bottom of R206/C208" here, just these part numbers don't exist in the Jr.). And, though is pretty obvious that you tapped TIA csyn on top of R51, TIA lum0 on top of R52, TIA lum1 on top of R49, I cannot find a pin labelled "lum2" on this site's PAL VCS Jr. schematics - you tapped the pin labelled "lum3" on top of R53 instead and this gives the same result?

Pin 6 of pal TIA is mislabeled ""LUM3" in the schematics of PAL jr. It's actually "LUM2".

post-10599-1216029406_thumb.png

 

I'd like to try this mod on a 6-switch NTSC console and thus cannot get color and audio from the same spots of the mainboard, that's why I'm asking: are there any resistors/capacitors/anything else between the TIA pins and the tapping points?

No, the COLOR and AUDIO points are continuous with the corresponding TIA pins, while the SYNC and LUM pins are connected to 4 CD4050 inputs and I tapped the signals from the corresponding outputs.

post-10599-1216029430_thumb.jpg

You should be able to find the right spots on your console using the NTSC TIA and CD4050 pinout. :)

post-10599-1216029415_thumb.pngpost-10599-1216029443_thumb.png

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on the foto where the console with the scart cable direct soldered to the circuit board you can see some kind of "thing" which is in the former RF hole... the cable is going through this thing...

what do you call this thing? i want to order something like that, but i dont know what the name is (neither in englisch nor in german :( )

post-10966-1219788613_thumb.jpg

Edited by Scorp.ius

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on the foto where the console with the scart cable direct soldered to the circuit board you can see some kind of "thing" which is in the former RF hole... the cable is going through this thing...

what do you call this thing? i want to order something like that, but i dont know what the name is (neither in englisch nor in german :( )

In English (UK) it would be called a rubber grommet, a motor facrors (car accessory shop) may have one

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Update: I have installed this mod into a PAL Atari Jr. console first. The picture is excellent in colour and clarity, though for my taste it's a little too sharp, as the brightness of colured objects, e.g. in H.E.R.O.

of the same colour varies horizontally when fed into the TV via S-video, while the same blocks look homogenous when I switch my TV to video (or did I simply make a mistake? It is the same for all scan lines though, and grey objects are not affected). This changing is extremely visible on my LCD TV, yet far less on my CRT TV.

 

Probably, I'll try "Lynx's 0,68 Euro ATARI 2600 Junior Composite Mod" next.

 

 

Thorsten

Edited by Thorsten Günther

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Hmm, looks like there's no stereo for PA - PAL-S takes the place of AUD1 while PAL-I takes the place of BLK. Anyone know what are those 2 PAL-x signals are?

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Update: I have installed this mod into a PAL Atari Jr. console first. The picture is excellent in colour and clarity, though for my taste it's a little too sharp, as the brightness of colured objects, e.g. in H.E.R.O.

of the same colour varies horizontally when fed into the TV via S-video, while the same blocks look homogenous when I switch my TV to video (or did I simply make a mistake? It is the same for all scan lines though, and grey objects are not affected). This changing is extremely visible on my LCD TV, yet far less on my CRT TV.

 

Probably, I'll try "Lynx's 0,68 Euro ATARI 2600 Junior Composite Mod" next.

 

I tried the Lynx mod in the meantime and the quality of the CD4050 mod is much higher. Still, I need to modify it to composite, as my LCD TV does show me a great picture via SCART (as video apparently, since the vertical gridding is gone when connected via a cheap s-video/video to SCART adaptor like this one. I tried jsopers method of putting the chroma into the same transistor as the chroma/csync leads (bad picture), a simple wire between the chroma and luma outputs (very bad b/w picture) and also an 18K resistor and 100 pF capacitor (hardly any color, very noticeable flickering).

 

Anyone got a good idea?

 

 

Thorsten

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Hey, sorry for the bump, but I was just trying this - minus the circuitry. I simply threw all the luma and color together, to test if it was working.

 

It is, but it's in black and white. Is this expected behaviour? If so - why?

 

 

Oh and yes, the switch is set to color on my console :roll:

 

Thanks for the help, and sorry for digging up the topic

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Hey, sorry for the bump, but I was just trying this - minus the circuitry. I simply threw all the luma and color together, to test if it was working.

 

It is, but it's in black and white. Is this expected behaviour? If so - why?

 

I experienced the same problem, but a simple 470pF ceramic capacitor cured it for me (just solder it between chroma and luma).

 

 

HTH, and sorry for the late reply,

 

 

Thorsten

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Hmm, looks like there's no stereo for PA - PAL-S takes the place of AUD1 while PAL-I takes the place of BLK. Anyone know what are those 2 PAL-x signals are?

 

It's the connection for the 4,43Mhz PAL colour crystal. Yes, the PAL TIA needs 2 clocks (3,55Mhz and 4,43Mhz) to function.

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Hello,

 

I tried the mod in the first post and I didn´t get it work.

I have an PAL Jr. and put Chroma/Luma together, I also tried the full mod with Cd4050 and get the same result.

I have a running picture and bad quality on one TV, on the other TV I have a running B/W picture and also bad quality.

I tried several capacitors between Chroma/Luma, no change.

 

Any Ideas?

 

Thanks for help.

Edited by Spyke

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Hello there,...

 

i did the cd4050 mod on my PAL 2600Jr. and i have a very dark picture. dont know why,... anyone has an idear?!

 

T.

 

 

done,.. it works!

Has anyone got pictures of this actual mod and also what is the picture quality on a LCD TV?

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Hello there,...

 

i did the cd4050 mod on my PAL 2600Jr. and i have a very dark picture. dont know why,... anyone has an idear?!

 

T.

 

 

done,.. it works!

Has anyone got pictures of this actual mod and also what is the picture quality on a LCD TV?

 

Probably very similar to my mod as it is based on the CD4050 except with a bit more bleed due to the use of the slower CD4050. Use a CD74HC4050 if you are using a LCD TV. Most CRTs will fudge the signal a bit and using the slower CD4050 won't make a big difference.

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Hello there,...

 

i did the cd4050 mod on my PAL 2600Jr. and i have a very dark picture. dont know why,... anyone has an idear?!

 

T.

 

 

done,.. it works!

Has anyone got pictures of this actual mod and also what is the picture quality on a LCD TV?

 

Probably very similar to my mod as it is based on the CD4050 except with a bit more bleed due to the use of the slower CD4050. Use a CD74HC4050 if you are using a LCD TV. Most CRTs will fudge the signal a bit and using the slower CD4050 won't make a big difference.

 

I have decided to just grab some of your MOD longhorn. It was so easy to install and S-video is sweet as.

Hopefully I can get it running correctly on a PAL tv.

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Any electronics component dealer. Here in Australia we have a chain called Jaycar that sells all sorts of connectors and din plugs.

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Tried this mod on a Revision "D" atari junior and only got a black screen, no picture at all.

It would be useful if those who got it to work would post the type of atari, ie 6 switch, 4 switch or junior and the motherboard revision they have.

So far from what information i've gathered it seems to only work on the Revision "B" junior.

Please help as currently there is no decent s-video mod for pal systems thats guarenteed to work.

Edited by Geffersan

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OK,

I finally got this damn mod working. Sort of.

The picture is nice and clear now.

I have just one problem. My TV constantly displays the S-video symbol. It flashes on screen.

If I go into the TV settings they flash up then disappear. I suspect there may be voltage running into the s-video.

Anyone else got something like this happening?

For anyone that wants it here is a perfboard diagram that I put together.

post-26369-129483254644_thumb.gif

post-26369-12948325761_thumb.jpg

post-26369-129483261467_thumb.jpg

post-26369-129483268022_thumb.jpg

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OK,

I finally got this damn mod working. Sort of.

The picture is nice and clear now.

I have just one problem. My TV constantly displays the S-video symbol. It flashes on screen.

If I go into the TV settings they flash up then disappear. I suspect there may be voltage running into the s-video.

Anyone else got something like this happening?

For anyone that wants it here is a perfboard diagram that I put together.

 

Found out what the problem was. Was using PN100 transistors instead of 2N3904 as I was told they are compatible. When replaced with the 2N3904's it works perfectly.

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