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ChaoticBiker

ANOTHER 2600 AV mod issues topic

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Hi all,
welcome to my thread which is ANOTHER one of those where AV mod only made things worse :D
So let me start from the beggining:
Atari VCS Heavy Sixer "Sunnyvale edition". Not sure if it's NTSC or PAL....
Before AV mod: unit working fine, or as fine as it could via RF antennae input.
Used the DIY mod with a voltage regulator and 2.2k, 3.3k and 75 resitors, kind of like this one https://www.ebay.co.uk/itm/133754808637
Also using an aftermarket power supply - 1A. Have also an aftermarket 0.5A. There's hardly any difference in the picture quality when using either.

After mod:
issue no.1 - NO picture (but sound!)
Solution no.1 - fiddled with the onboard potentiometer only to receive a very faint picture (it turned out later, the picture was always there - it was just very, very dim)

issue no.2 picture extremely faint, recognised only on some TV's/monitors
Solution no.2 - removed the 75 ohm resitor, as advised on the forums here. IMPROVEMENT! Now I can atually see what's on the screen, and even play!

issue no.3 is two part. while solution 2 improved the situation and picture is now recognised on almost all my TV's and monitors...
3.a) the colours are wrong. It also looks like there's no yellow? fiddling with the onboard potentiometer only goes through a variety of colour pallets, all of them wrong, with B/W in between.
3.b) the picture is still quite faint. Can see enough to be playable, but nowhere what I'd expect it to be. Also the more modern TV's will only in some cases hold colour for a minute or two, before going greyscale. Older CRT monitors don't display this behaviour.
So far no solution to this one...

I've tried following some advice on the forum here, with various people reporting AV mod issues, so what I tried so far:
replacing the 2.2k and 3.3k resistors with 4.7k and 6.8k - this appear to have changed absolutely nothing. I currently have the 4.7 and 6.8 put in, but happy to experiment if you fine folk recommend this way.
I have replaced two caps in my Atari, the big 2200uF one, and C201 - it did not change anything. Suggestions what else I might need to replace?
Adding back the 75ohm resistor only makes the picture go completely dark, but from what I can see - the colours are still wrong.

Running out of ideas here, and if it's going to be like that, I'm just going to revert back to the RF modulator (which I very much like to avoid)
To reiterate, the atari worked fine, correct colours etc. through RF before the mod.

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Rip it out and replace it with a UAV and call it a day.

 

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15 hours ago, -^CrossBow^- said:

Rip it out and replace it with a UAV and call it a day.

 

that' some solution, but UAV kits don't seem to be available in the UK, and not wanting to wait months and pay over the odds to have it imported from the US of A. Unless someone points me where to get this in UK?
Might eventually go this way, but for now just trying to fiddle with what I have.

So far I've replaced another thing on my 2600, the  7805 voltage regulator. It improved picture stability, an issue I thought was related to the TV I was using for testing but now turns out picture is better. Also tested in on the LCD that was losing colour after a minute or so - this does not happen anymore, so yay!
Still wrong colours though. 

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Wrong colors is typically either the potentiometer or the voltage to it.  What is the DC voltage of your power supply under load?

 

The kit you linked to does not have a voltage regulator.  Just a transistor and some resistors.  What instructions did you follow?

 

And since it's a heavy sixer, check that the ribbon between the two boards is still in good shape.  Should be flexible and not delaminating.

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2 hours ago, ChildOfCv said:

Wrong colors is typically either the potentiometer or the voltage to it.  What is the DC voltage of your power supply under load?

 

The kit you linked to does not have a voltage regulator.  Just a transistor and some resistors.  What instructions did you follow?

 

And since it's a heavy sixer, check that the ribbon between the two boards is still in good shape.  Should be flexible and not delaminating.

Thanks for the insights, I'll check the voltages - but there's one more thing I feel I need to do.
Instructions followed were for hte standard DIY AV mod, which involve removing a few components off the board (I kept all the original components - though if replacing would preferably use new ones)
That one thing to do - I noticed the green mylar capacitor 0.22 100v which is right next to the power switch does not look right - it looks bloated, especially when compared against pics of similar boards on the internet. Don't have a replacement at hand, but ordered one and will replace it as after checking around I believe it might responsible for picture and colours. Will update after replacement (which most likely will be after the weekend)

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9 hours ago, ChaoticBiker said:

Instructions followed were for hte standard DIY AV mod, which involve removing a few components off the board (I kept all the original components - though if replacing would preferably use new ones)

Yeah but most standard instructions don't require you to build the entire circuit.  They give you a PCB instead of a stripboard.  It may be beneficial to show a picture of your assembled board (both sides).  Dim or nonexistent video is often a problem of no +5V to the transistor.

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13 hours ago, ChaoticBiker said:

that' some solution, but UAV kits don't seem to be available in the UK, and not wanting to wait months and pay over the odds to have it imported from the US of A. Unless someone points me where to get this in UK?
Might eventually go this way, but for now just trying to fiddle with what I have.

So far I've replaced another thing on my 2600, the  7805 voltage regulator. It improved picture stability, an issue I thought was related to the TV I was using for testing but now turns out picture is better. Also tested in on the LCD that was losing colour after a minute or so - this does not happen anymore, so yay!
Still wrong colours though. 

I also did not know know you were in the UK or I might not have suggested or said anything. My apologies. But as @ChildOfCv stated, we will need to see full pics of everything to try and get an idea on this.

 

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Please accept my apologies if any of my previous posts came as abrupt or rude. They were not meant to be to be perceived as such.

I do value and consider every suggestion given, and am very thankful for the engagement on these forums, as it is always very helpful to have more experienced people sharing their knowledge.

I have replaced the .22k 100v green cap I mentioned in my previous post, as it looked quite dodgy. No change to the picture, unfortunately.
Here's the choice of colours I am getting now. Excude the glow, the sun appears to be in full shine today, making it a tad difficult to take photos of the screen.  You have to trust me, the picture is very bright and sharp - it's just wrong colours!
. In the below examples, the colours are very obviously wrong in every case. This is what happens when I play about with the potentiometer on the board. All of these are obviously ranges, with slight differences on the start of the range to finish. Position 1, which is potentiometer turned almost completely counter clockwise appears to be closest to what it should be.
_20211115_145556.thumb.JPG.1844d8c991eef9162a0c7d34878a349d.JPG
_20211115_145620.thumb.JPG.f4cb30951fac22b1bfa45fa32b8ba01a.JPG
_20211115_145634.thumb.JPG.5c841c7eb14cbe1c23842a8975110ec6.JPG

And here's my hackjob of an AV mod. Please note, when it comes to soldering, I have no idea what I'm doing yet somehow my mods work, usually well within the first 15 attempts.
It did look a lot nicer when it was first put together, but since then it had numerous resistors added/removed to it. It currently has a 4.7k and a 6.8k resistor, and no 75ohm as if I add one, the picture goes very dim. Current resistors have been purposefully soldered without legs being cut, to allow easy desoldering if/when required. There do not appear to be any unwanted connections /shorts between any of the lines - checked using a multimeter.

DSC_0331.thumb.JPG.b2650105e066d41ec3ae4b0c6bdab423.JPG
Oh and don't mind the yellow tape - it's only there to hold the board in place. And the silver 4.7uf cap has been just replaced as well.


Instructions for pins I followed from here https://www.thefuturewas8bit.com/atari_2600_6_pal
I've lost the printout I had for soldering the pins onto the board, but it was pretty straightforward, usually just wires in place of removed components.
You might notice there's some extra wires coming out the board - pretty much double the amount. Reason for that is, they were soldered originally into them pins right next to where the original RF module was. Since initially I thought that was the issue, I then soldered them to points on the board - with no change at all. They are currently soldered in both places - pins next to the mod, and points on the board
top line - whice wire and then blue is pass through for Audio. no issues there.
2nd line from top is video out. it is connected to 3rd line down
3rd line has the transistor out. It's purposefully shorted to line 2 but not to 4th. (it's Video OUT)
4th line from top with yellow wire going to the board and black to pin 4. It connects to the middle pin of the transistor (video IN)
5th and 6th lines are empty
7th line has the +5v - drawn from two places atm, from the board and from pin 3 next to the av mod. There's the 4.7k resistor connecting line 7 with line 4
8th line is GND and 6.8k to 4th line - middle leg on the transistor / video in

Since I started this thread, I solved all issues regarding: brightness and sharpness or colour seep/loss. Mostly thanks to replacing caps and the voltage regulator.
All I'm left with, is to get the colours right.
 

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7 hours ago, ChaoticBiker said:

All I'm left with, is to get the colours right.

There is a potentiometer wheel on the board that can adjust that. Just make sure you mark where you start before making any adjustments so you know where to put it back to in the event you make it completely off.

 

image.thumb.png.be4057d3771553f5588ca58ad8ca17be.png

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3 hours ago, Dopy25 said:

There is a potentiometer wheel on the board that can adjust that. Just make sure you mark where you start before making any adjustments so you know where to put it back to in the event you make it completely off.

 

image.thumb.png.be4057d3771553f5588ca58ad8ca17be.png

Pretty sure he stated further up he had tried to adjust the colors using the trimmer and his screenshots so the extent of range of colors he is getting with the adjustment, none of which actually seem to be completely correct though.

 

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28 minutes ago, -^CrossBow^- said:

Pretty sure he stated further up he had tried to adjust the colors using the trimmer and his screenshots so the extent of range of colors he is getting with the adjustment, none of which actually seem to be completely correct though.

 

You're right. But it might be worth trying again now that they've corrected the other video issues.

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12 hours ago, ChaoticBiker said:

Instructions for pins I followed from here https://www.thefuturewas8bit.com/atari_2600_6_pal
I've lost the printout I had for soldering the pins onto the board, but it was pretty straightforward, usually just wires in place of removed components.
You might notice there's some extra wires coming out the board - pretty much double the amount. Reason for that is, they were soldered originally into them pins right next to where the original RF module was. Since initially I thought that was the issue, I then soldered them to points on the board - with no change at all. They are currently soldered in both places - pins next to the mod, and points on the board
top line - whice wire and then blue is pass through for Audio. no issues there.
2nd line from top is video out. it is connected to 3rd line down
3rd line has the transistor out. It's purposefully shorted to line 2 but not to 4th. (it's Video OUT)
4th line from top with yellow wire going to the board and black to pin 4. It connects to the middle pin of the transistor (video IN)
5th and 6th lines are empty
7th line has the +5v - drawn from two places atm, from the board and from pin 3 next to the av mod. There's the 4.7k resistor connecting line 7 with line 4
8th line is GND and 6.8k to 4th line - middle leg on the transistor / video in

Since I started this thread, I solved all issues regarding: brightness and sharpness or colour seep/loss. Mostly thanks to replacing caps and the voltage regulator.
All I'm left with, is to get the colours right.
 

What is the part number of the transistor that they gave you?  You should be able to read it on the flat side.  It may be wrapped around a few lines.  Also, you didn't say what you attached the 3rd transistor pin to.

Edited by ChildOfCv

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4 hours ago, ChildOfCv said:

What is the part number of the transistor that they gave you?  You should be able to read it on the flat side.  It may be wrapped around a few lines.  Also, you didn't say what you attached the 3rd transistor pin to.

yes sorry I missed that. The 3rd pin on the transistor is attached to line 7  - that's +5v
the markings on this transistor appear to say it's 2N 3904 -A25

 

5 hours ago, Dopy25 said:

You're right. But it might be worth trying again now that they've corrected the other video issues.

Was hoping this would be the case, but no. Screenshots roughly show variations of pallette I am able to get using the potentiometer. There's a momentary B/W between each of them, and each pallette has a slight variation as the range goes by, but not enough to warrant additional screenshots.
It's almost like it cannot strike the balance between the three main colours... RGB... like one has not enough red, the other not enough green, and third not enough blue..
I wonder if I now re-attach the 75ohm resistor, which would go between GND and VIDEO OUT, would it change anything...av-mod-schematics.png.27425ed57df96c5b6737db68d6f34d04.png

Initially removed as it was making the pic very dim, at the very start of troubleshooting, but then I also replaced a lot of things so maybe now it will make a difference

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Honestly I don't think I've ever seen someone use veroboard upside down before. But it was like that in the ebay ad I suppose.


FWIW if it worked here via RF it's a PAL machine. NTSC RF tuners in TV's here are unheard of unless you've imported a US TV.

 

If you want to do it yourself, order a UAV direct from The Brewing Acedemy. They get here, they end up costing around £35 all up. It's going to be the easiest DIY solution.

 

Or you can send it to us and we'll sort you out with a better mod than the one from ebay...

Edited by juansolo
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On 11/15/2021 at 7:23 AM, ChaoticBiker said:

They are currently soldered in both places - pins next to the mod, and points on the board

I'm not sure this suggestion will help, but you might try only one connection to the board and not 2. It may be that one of the board connections is in the wrong location or passing through another component. If you thought the first connection could be an issue, try removing that and using your second connection. 

 

Try using the connections only at the removed components.

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The screenshots posted above show a NTSC version of "Pitfall II" running on a PAL console.

You'll never get correct colors with that combination (unless you install the RGB mod, which bypasses the 2600 color generation and allows to switch between NTSC and PAL palettes).

 

You need to use PAL games.

 

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9 minutes ago, Dopy25 said:

I'm not sure this suggestion will help, but you might try only one connection to the board and not 2. It may be that one of the board connections is in the wrong location or passing through another component. If you thought the first connection could be an issue, try removing that and using your second connection. 

 

Try using the connections only at the removed components.

Thank you, yes I though about that and tried it - no difference whether I use pins next to AV mod or the points on the board. Plus the way they're placed, little chance of them connecting to anything they shouldn't have
However, once I get to soldering back the original resistors (which should be hopefully end of this week), I'll clean up and remove the excessive wires, as there's no longer any need for them.
I'll update what happens then.

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12 minutes ago, alex_79 said:

The screenshots posted above show a NTSC version of "Pitfall II" running on a PAL console.

You'll never get correct colors with that combination (unless you install the RGB mod, which bypasses the 2600 color generation and allows to switch between NTSC and PAL palettes).

 

You need to use PAL games.

 

LOL.
That worked.

seriously. :lol:

As suspected, I am an idiot. 🙃

Perhaps need to add a bit of background at this point:
I had very few original carts, with a P on it, assuming this means PAL.
Then I came into possession of a larger library which someone was throwing out - carts which do not have a P on them. I assume they're all NTSC then.
This was what prompted me to do the AV mod in the first place - so I can enjoy playing these.

Well I guess it's back to the Uno Cart :D

I will check all of them and yeah basically everything that throws the odd colour I'll put aside as NTSC. :D Luckily there's a retro convention happening next weekend in Glasgow, might try to sell them off there.

I actually believed it was an NTSC console. How do I tell by looking at it? there's nothing immediately on either the box or on/inside the console that would tell one way or the other.

Thank you all for your contributions.
I do not consider all these capacitors and resistors replaced as wasted - the picture is indeed much improved and overall I hope I extended the life of my system.
Also, the more you know 🤪
lessons learned!

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I'm sure there are other ways, but in this case, you look at the TIA chip as they are different between the NTSC and PAL versions. 

 

NTSC TIA is usually PN = CO104444D

PAL TIA is listed as PN = CO11903

 

 

 

 

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3 hours ago, juansolo said:

Honestly I don't think I've ever seen someone use veroboard upside down before. But it was like that in the ebay ad I suppose.

The reason it's like that is to allow easy addition/removal of components without having to lift and turn it around each time. 

I kind of expected it to not work the first time around.

 

Also, the total cost of my mod as it stands, with all the extra replacement capacitors etc was less than £15 in total.

The education and experience gained though! 

 

And still got enough leftover components to make a couple more, just need to buy transistors as only had one. 

Migh attempt to AV mod that 2600 clone I have as well

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13 hours ago, ChaoticBiker said:

yes sorry I missed that. The 3rd pin on the transistor is attached to line 7  - that's +5v
the markings on this transistor appear to say it's 2N 3904 -A25

 

Was hoping this would be the case, but no. Screenshots roughly show variations of pallette I am able to get using the potentiometer. There's a momentary B/W between each of them, and each pallette has a slight variation as the range goes by, but not enough to warrant additional screenshots.
It's almost like it cannot strike the balance between the three main colours... RGB... like one has not enough red, the other not enough green, and third not enough blue..
I wonder if I now re-attach the 75ohm resistor, which would go between GND and VIDEO OUT, would it change anything...av-mod-schematics.png.27425ed57df96c5b6737db68d6f34d04.png

Initially removed as it was making the pic very dim, at the very start of troubleshooting, but then I also replaced a lot of things so maybe now it will make a difference

The 75-ohm resistor is unnecessary as specified and just works the transistor harder.  If you use the 75-ohm, place it in series with the video out, not between video out and ground.  This creates the sending end of the 150-ohm voltage divider that AV inputs expect.  That should minimize ghosting.

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