Strange scanline effect on composite modded 6Woody

[jaguarwong]

I had a 6 Switch Woody (PAL) with no RF output at all.

I generally don't agree with modding but in this case I considered fitting a Composite mod from The Future Was 8 Bit as more of a repair.

 

Unfortunately, while the mod is now giving me a picture, there is a strange problem where the scanlines are showing in alternating colours.

I've attached a picture of H.E.R.O. running below and you can see that the right side of the power bar (that should be red) is instead alternating red and green across the scan lines.

 

I've tried twiddling the colour pot and reseating the chips and this has had no effect.

 

Anyone got any ideas?

 

Thanks in advance

[cwilkson]

Not unexpected.  PAL is funny like that.  Although I admit I'm no PAL expert....I'm more of an NTSC master.

 

"Phase...Alternating...Line"

 

It's nice when it works.  But it does things every other line that can lead to things like your display if the mod isn't playing nice.

 

I think that one is just a transistor buffer.  Do you have a schematic of the mod?  And how it's installed?

 

[jaguarwong]

9 hours ago, cwilkson said:

 have a schematic of the mod?  And how it's installed?

 

Hi, thanks for the reply, any and all of the technical and installation into I have is from the TFW8b page: https://www.thefuturewas8bit.com/deluxe-atari-composite-video-mod.html

[jaguarwong]

Sorry to sound needy, but I also found this http://blog.tynemouthsoftware.co.uk/2018/05/easy-atari-2600-vcs-composite-video-mods.html which appears to be the person who made it. A lot of info on there going right over my head.

 

I've dropped them a line directly, too.

Edited October 20, 2020 by jaguarwong

[jaguarwong]

2 hours ago, jaguarwong said:

Sorry to sound needy, but I also found this http://blog.tynemouthsoftware.co.uk/2018/05/easy-atari-2600-vcs-composite-video-mods.html which appears to be the person who made it. A lot of info on there going right over my head.

 

I've dropped them a line directly, too.

Turns out that guy didn't make it, just made that detailed blog post about fitting it. He suggested the issue might be the TIA chip though. Thoughts?

[cwilkson]

4 hours ago, jaguarwong said:

Turns out that guy didn't make it, just made that detailed blog post about fitting it. He suggested the issue might be the TIA chip though. Thoughts?

Thanks for the links.   I'm swamped until the end of the week.  I'll take a look then.

 

BTW, I think I got rid of my PAL 2600 a few years back so it'll all be guess work.  But I'll see what I can come up with.

 

Did your 2600 do that pre-mod?

[jaguarwong]

3 hours ago, cwilkson said:

your 2600 do that pre-mod?

It did nothing pre-mod. I only did it cause I couldn't get a picture through the RF.

 

And I'm not going to 'choosing-beg' over here, I'll take any help I can get, whenever I can get it. I don't want to put anyone out. Thank you.

[pcrock]

On 10/19/2020 at 12:10 PM, jaguarwong said:

I had a 6 Switch Woody (PAL) with no RF output at all.

I generally don't agree with modding but in this case I considered fitting a Composite mod from The Future Was 8 Bit as more of a repair.

 

Unfortunately, while the mod is now giving me a picture, there is a strange problem where the scanlines are showing in alternating colours.

I've attached a picture of H.E.R.O. running below and you can see that the right side of the power bar (that should be red) is instead alternating red and green across the scan lines.

 

I've tried twiddling the colour pot and reseating the chips and this has had no effect.

 

Anyone got any ideas?

 

Thanks in advance

It seems to be a problem at TIA CHIP.

Is the TIA soldered to the board or does it use a socket?

If it is soldered, try resolding it and if it is in a socket, try a new socket and cleaning all the CHIP terminals before reinstalling it.

The CHIP may also be defective.
You could also have any SOUND oscillator´s signal being mixed with the video signal. Did you remove the transistor and inductor from the audio mixer oscillator circuit?
May I see the schematics for the console you own???

Edited October 20, 2020 by pcrock

[jaguarwong]

11 hours ago, pcrock said:

It seems to be a problem at TIA CHIP.

Is the TIA soldered to the board or does it use a socket?

If it is soldered, try resolding it and if it is in a socket, try a new socket and cleaning all the CHIP terminals before reinstalling it.

The CHIP may also be defective.
You could also have any SOUND oscillator´s signal being mixed with the video signal. Did you remove the transistor and inductor from the audio mixer oscillator circuit?
May I see the schematics for the console you own???

The chip is socketed so I've given it a clean with no improvement

It's a PAL 6 Switch Woody, I removed the components labelled R209, L201, Q202, R216 as instructed with the mod. There's more details in the reply above but I'm afraid I'm not technical enough to know any more than that.

[jaguarwong]

Little update in case anyone stumbles on this and wants to help - Iwas able to try a slightly different, simpler mod and the result was exactly the same.

 

So, heading down the TIA line of investigation, is a UM6526P1 going to work with this model 2600? It's the only one I can see available but the description says it's for a Jnr.

 

Cheers

[pcrock]

The UM6526P1 is indeed the PAL version of the TIA. ( I think is the same as CO11903) and both may have NO THE SAME pinouts than 6526N!!!!!!
UM6526N, KSC131 and CO10444D, are the NTSC version!!!
Please take a look below for more...