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Simple DIY composite video mod

Atari 2600 Composite Video Mod

68 replies to this topic

#26 simon.plata OFFLINE  

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Posted Mon May 21, 2018 10:28 AM

Hi, can be installed on PAL Light sixer too? I see that this circuit best suits NTSC... seems to be better than this one https://www.thefutur...-video-mod.html

 

Hi, it was designed for NTSC bandwidth in mind which is a bit lower tan PAL. However "boggis the cat" used it on a PAL 2600A and worked fine (please see entry #11 above). That means it supported the PAL bandwidth. It should work on a sixer. Only needs to identify the components needed to be removed and the corresponding connection points. The two stage transistor design worked very well for me over all other single stage that I tested before.



#27 Blackgear OFFLINE  

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Posted Tue May 22, 2018 6:14 AM

 

Only needs to identify the components needed to be removed and the corresponding connection points. The two stage transistor design worked very well for me over all other single stage that I tested before.

 

Yeah, this is the hard part... someone can tell me if this guide is right for this mod? https://www.thefutur...tari_2600_6_pal

 

I've just repaired my "new" sunnyvale light 6er, don't want to burn all my "hard" work.



#28 af0l OFFLINE  

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Posted Tue Jun 5, 2018 5:54 AM

 

Yeah, this is the hard part... someone can tell me if this guide is right for this mod? https://www.thefutur...tari_2600_6_pal

 

 

I'd like to know that too...



#29 boggis the cat OFFLINE  

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Posted Thu Jun 7, 2018 4:16 AM

Yeah, this is the hard part... someone can tell me if this guide is right for this mod? https://www.thefutur...tari_2600_6_pal
 
I've just repaired my "new" sunnyvale light 6er, don't want to burn all my "hard" work.

  

I'd like to know that too...


If your PCB looks like that shown, then those instructions should be good. My 4-switch ‘Vader’ model is an odd-ball made in New Zealand back in the day, but the basic board layout was the same.

If your PCB looks slightly different it may still use the same component designation, so look for the printed labels — often under components, for extra fun. Check by tracing the path back to another component — the audio will always come from the same source, and so with the video. A ground point and 5 V source can be taken from anywhere convenient, really.

Just take care, and make sure you can reverse any change if necessary. I only lifted one end of components to be removed, then used a bit of heat-shrink to isolate them. This made the changes reversible. Getting the modulator out took a lot of effort, so you may want to consider leaving it in place and just cutting the five pins close to the board then taking them out. (It is a large piece of metal, so desoldering it was difficult. I would try to leave it in place if doing this again.)

The circuit provided by “simon.plata” is pretty simple, but I built it on a breadboard first and connected it up to test prior to building on the small piece of PCB. My first attempt at the small PCB failed due to not laying the components out well. You can use the schematic for the PCB that Simon put here to guide you in building this on your own PCB.

#30 af0l OFFLINE  

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Posted Mon Jun 11, 2018 1:57 PM

I tried this on my light sixer and managed to ruin it. I removed both resistors, the transistor and the coil. Desoldered the modulator. I get relatively clean 5V on pins 1 and 3, but pin 4 where the video should be shows just constant high potential buzz... Help... Anyone?

Forgot to say, I dropped the channel switch too...

#31 boggis the cat OFFLINE  

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Posted Thu Jun 14, 2018 2:56 AM

I tried this on my light sixer and managed to ruin it. I removed both resistors, the transistor and the coil. Desoldered the modulator.


Check that these are the correct components. Different boards may have different configurations.

I get relatively clean 5V on pins 1 and 3, but pin 4 where the video should be shows just constant high potential buzz... Help... Anyone?


You shouldnt get 5 V on two pins. High potential meaning > 2 V?

If you can take some photos of your board then people may be able to help.

Also, an oscilloscope is useful to trouble-shoot if you have access to one.

Edited by boggis the cat, Thu Jun 14, 2018 2:57 AM.


#32 af0l OFFLINE  

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Posted Thu Jun 14, 2018 3:03 AM

Thanks Boggis, I expressed myself awkwardly there. It's 0V on pin 1 and 5V on pin 3, as it should be. I'll post phots too.

 

And I have access to several oscilloscopes, my father designs electronics. It's just that we used a brand new one that even he is unfamiliar with, so I couldn't really tell you if that's 2V on pin 4. :)

 

I'll make pops work with me on this over the weekend, I hope. Meanwhile I read somewhere that faulty TIA might be the cause of the flatline, so I'm having one mailed in from UK...

 

Will report back, thank you!



#33 boggis the cat OFFLINE  

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Posted Fri Jun 15, 2018 7:09 AM

If the system was working before you attempted the mod then it may not be the TIA. You may also want to check the RIOT chip, if the system just produces static or a bad picture (but a picture is being output: use a ‘scope set to detect the PAL TV trace).

They can die, of course. I repaired the unit I modified, and it turned out to have a bad RIOT chip. (Bought five replacements, two were DOA.* Also bought two ‘working’ TIA chips, one of which was DOA. These are getting old and becoming cranky.)

* Weird effects can be had from bad RIOT chips. I tested the five out, and one just wouldn’t work somclearly dead. One created some interesting effects on Pac-man: the joystick only worked down and left, and poor old paccy got embedded in the wall at the left of the playfield — bad RAM locations, I am guessing. (OTOH, the ghosts couldn’t reach him. Glass half full? )

#34 af0l OFFLINE  

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Posted Fri Jun 15, 2018 4:37 PM

So, this is the pretty thing we're dealing with... I resoldered the resistors and the coil, as some mod instructions do not mention removing those, but to no avail. Still nothing good happens on pin 4...

 

IMG_2014.jpg

IMG_2013.jpg



#35 boggis the cat OFFLINE  

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Posted Fri Jun 15, 2018 5:56 PM

I have highlighted (yellow circles) some potential bad solder joints. Check continuity, and preferably redo these and any others that look dirty or appear to not contact the components and/or board well (dry joints).

C6F5BDB6-93EE-43FA-8CEE-F52DE59D0C7D.jpeg

More suspect solder points, and a possible crack in a track (red arrow). Check continuity across that track, while putting (slight!) pressure on the reverse side. If it is faulty then route a wire to bypass it.

B1FD96CF-9701-4E8C-A5B6-1E8F53AB4923.jpeg

After checking and fixing those solder points, try putting the transistor back and test if the system functions again. If so, then the ICs are OK.

If you want to get a spare RIOT chip, they go by the part number UM6532, and are fairly widely available (eBay or Aliexpress or etc).

Best of luck getting this working. It can be frustrating, but take your time and check your work as you go.

#36 af0l OFFLINE  

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Posted Mon Jun 18, 2018 4:39 PM

Thank you Boggis, I did check all the points you marked - some were my "reflows" with too low temperature set on the soldering iron... In the end I decided to go your way and reinstall everything as it was. And it did not work. I remembered the sixer being quirky at times, which was the main reason I decided to open it in the first place. So I poked around with a stick (an old toothbrush in this case), and when I knocked on TIA, I got the picture back!

 

Now we know it was not the TIA, but the darn socket underneath it. Or maybe there was a bad joint underneath, anyway, I quickly replaced the socket (sadly, along with some of the pads underneath) - and lo and behold - the picture is back, steady and even works on composite. There are not many happier 2600 owners in this town tonight.

 

Thank you Boggis the cat, your hints were the right ones. You are to be credited for this light sixers coming years of providing fun in our home.

 

IMG_2038.jpg

 

IMG_2037.jpg



#37 boggis the cat OFFLINE  

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Posted Tue Jun 19, 2018 5:25 AM

Thats good news. Always good to get a pay off from investing so much time in these creaky old machines. 👍

I replaced my TIA socket, too, as I was suspicious of it. However, it turned out to be the RIOT chip that had died. (Not a bad idea to replace sockets that look in bad condition, anyway.)

Did you need to tweak the sound level at all? I found that the output was way too high, and ended up putting a fairly high resistance in series to drop it to a reasonable level.

#38 af0l OFFLINE  

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Posted Tue Jun 19, 2018 2:28 PM

Hmm, I didn't get that far yet... I'm playing with removing individual components as per the instruction from thefuturewas8bit. ATM it still loks best on the RF :)

I have to make the board properly, then I'll see the real picture. But I'd say that the sound probably needs some dampening - or the OP would't have done it so? How much did you end up putting in?

#39 boggis the cat OFFLINE  

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Posted Wed Jun 20, 2018 7:14 AM

But I'd say that the sound probably needs some dampening - or the OP would't have done it so? How much did you end up putting in?


33K seemed to be about right. You may have to experiment a bit, or check the audio level on an oscilloscope — about 1 Vpeak seemed reasonable on the TV I used (although I think the standard may be 1 Vrms, or 1.4 Vpeak). Ideally, you want each signal amplitude — video and audio — to be as close as possible to specification.

#40 af0l OFFLINE  

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Posted Mon Jun 25, 2018 3:36 AM

I just put in the 10K resistor in the end. It sounds pretty cool, but I have yet to attach a scope to it.

 

The video is not decidingly better after the mod. I thought it would rid me of color bleeding, but it didn't. Still, the picture seems to be more solid, and I can hook the 2600 to monitors I couldn't before, so high fives all around.

 

But to be fair, there are some things to be considered when judging the quality of the output. The cable connecting the switchboard to the mainboard was failing. After the 4th wire broke, I lost my temper and soldered in a board to board connector. So that may have some impact. I also used the same kind of connector to connect my mod board. That way I coud just plug it out when needed and not need to resolder it every time, which would definitely ruin the switchboard.

 

So, while I tortured this poor thing long enough, I just might get another 2600 and do it all over again. It was fun. :)



#41 sirlemonhead OFFLINE  

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Posted Mon Jun 25, 2018 5:30 AM

Noob question, but do the resistors need to be any particular wattage or would 250mw or smallest size work OK?

 

Also, is there a capacitor in the circuit or not?

 

I can put this together no problem but just a little unsure of what parts to order :)



#42 boggis the cat OFFLINE  

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Posted Mon Jun 25, 2018 7:01 AM

Noob question, but do the resistors need to be any particular wattage or would 250mw or smallest size work OK?

I used 250 mW rated metal film. Probably anything would work fine, as no significant power is involved.
 

Also, is there a capacitor in the circuit or not?

You can add one in to blur the video if it appears too sharp, as Simon showed. I didnt use one, so it is optional.
 

I can put this together no problem but just a little unsure of what parts to order :)

Use the parts and board layout that Simon posted in post number 13, here: http://atariage.com/...-mod/?p=3895187

Edited by boggis the cat, Mon Jun 25, 2018 7:02 AM.


#43 sirlemonhead OFFLINE  

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Posted Wed Jun 27, 2018 4:33 AM

Cool, thanks! Have the bits on order so should be attempting this tomorrow hopefully :)



#44 Blackgear OFFLINE  

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Posted Wed Aug 1, 2018 12:28 PM

Just build in a proto board.
Have the same issue with the betagamma 2600vcs audio video mod... Sigh

Attached Thumbnails

  • IMG_20180801_202512.jpg

Edited by Blackgear, Wed Aug 1, 2018 12:29 PM.


#45 Blackgear OFFLINE  

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Posted Wed Aug 1, 2018 4:10 PM

The issue is about the verticale Lines.. seems there's shifted pixels. With this mod I have also some shadows in video, but It's only a proto..

#46 stlouisrod OFFLINE  

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Posted Sun Sep 16, 2018 2:29 PM

Not to hijack this great thread, but I'm having an odd pixel coloring issue with a similar mod I installed from best electronics CA. Hoping the thread owner might have some suggestions... BECA has no suggestions for me. They provided a different transistor than the one used in this mod, as well as more resistors to replace original ones. I've also replaced numerous capacitors and the voltage regulator just in case the old ones were waning, but results are the same. Thanks.

 

http://atariage.com/...composite-hack/



#47 boggis the cat OFFLINE  

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Posted Mon Sep 17, 2018 4:38 AM

The issue is about the verticale Lines.. seems there's shifted pixels. With this mod I have also some shadows in video, but It's only a proto..

The only suggestion I have is to check this on another display. It looks like a timing issue with the interlacing of the picture.

Possibly you could find some information by doing a search on this subject, if it is consistent across two or more displays.

#48 boggis the cat OFFLINE  

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Posted Mon Sep 17, 2018 4:45 AM

Not to hijack this great thread, but I'm having an odd pixel coloring issue with a similar mod I installed from best electronics CA. Hoping the thread owner might have some suggestions... BECA has no suggestions for me. They provided a different transistor than the one used in this mod, as well as more resistors to replace original ones. I've also replaced numerous capacitors and the voltage regulator just in case the old ones were waning, but results are the same. Thanks.
 
http://atariage.com/...composite-hack/

If it is a general colour issue then you can use the colour adjustment for that. If it is something like shimmering colours then that may be a display issue: test on another display to verify that it isnt a compatibility issue.

Recheck your modification points to be sure that you havent overlooked something. Possibly you may have accidentally shorted a couple of components.

If you can post a photo it may help as someone may have had the same issue.

Edited by boggis the cat, Mon Sep 17, 2018 4:46 AM.


#49 stlouisrod OFFLINE  

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Posted Tue Sep 18, 2018 6:56 PM

20180918 191559[1]
20180918 191620[1]


#50 boggis the cat OFFLINE  

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Posted Wed Sep 19, 2018 6:50 AM

That construction technique is going to be prone to problems. I would start by looking at how close the component legs are to other solder joints —that transistor looks to be very close to the pads below, for example. That proximity may be producing an interaction that you don’t want.

Ideally, you want to keep components well isolated and any wires as short as possible. That cable is unshielded and may be acting as an antenna, or a path for unwanted electrical interaction.

It could be that the problem is unrelated to the additional components, too. Perhaps an existing connection was compromised in some way — a chip not making correct contact to all points in the socket, a socket having a bad solder joint, a damaged pad or track... Unfortunately, a lot of things can be wrong.

If you can put up a photo of the output on the display that shows the problem that you are getting, or a short video clip if that gives a better example (e.g. colours shifting over time), then it may help figure out the cause.





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