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video fuzzy even after composite A/V mod

repair fuzzy video a/v mod troubleshooting

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#1 Divarin OFFLINE  

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Posted Fri Apr 19, 2019 6:19 AM

I have a vader model, I've replaced the RIOT chip, the 4.7uf caps, the 2200uf cap, and the voltage regulator.  Once I got it running again I noticed the video was fuzzy.  I decided to do an A/V mod and picked up this kit: https://www.ebay.com...872.m2749.l2649

 

Side note: as others have mentioned in other forums about the a/v mod the video was dark, after removing one of the resistors from the mod circuit that solved that issue.

 

The picture, however, is still fuzzy.  I've uploaded a video showing what I mean: https://youtu.be/UXzVRivc258

 

Not sure where to look next, any suggestions?  I have tried multiple composite cables and televisions as well so I'm pretty sure it's an issue on the board itself.


Edited by Divarin, Fri Apr 19, 2019 6:20 AM.


#2 diablonet OFFLINE  

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Posted Fri Apr 19, 2019 8:02 AM

Be sure that you replaced the ".22uF, 100V Metallized Polyester Film Capacitor", there are two in the 2600 4 switch.

 

those capacitors are related to snowy screen.



#3 diablonet OFFLINE  

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Posted Fri Apr 19, 2019 8:15 AM

Those are C241 and C242, use this page as reference: https://console5.com...s-and-more.html



#4 Divarin OFFLINE  

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Posted Fri Apr 19, 2019 9:35 AM

Great I'll give that a try thanks!

#5 Divarin OFFLINE  

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Posted Fri Apr 19, 2019 12:09 PM

Well, replaced those as well as c204 (since I had a spare for that thought I might as well even if it's not related) unfortunately it didn't seem to change anything.
Could be this will end up being a parts 2600 :(

#6 ChildOfCv OFFLINE  

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Posted Fri Apr 19, 2019 3:00 PM

Do you mean that it wasn't fuzzy before the replacement work?



#7 Divarin OFFLINE  

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Posted Fri Apr 19, 2019 5:51 PM

No it was fuzzy before. The first replacement I made was the riot chip, before that it was non-functional. After replacing the riot it worked but was fuzzy.

#8 ChildOfCv OFFLINE  

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Posted Sat Apr 20, 2019 12:21 AM

Oh okay.  Well, the fuzziness in your photo seems to slowly creep up the screen, which means it's probably closely related to wall current.  The TV draws half the picture about 59.9 times per second, and wall power is 60Hz (well, assuming you're in the US), so a 60Hz interference signal stays pretty closely sync'd to the TV picture.

 

So the first thing to consider is, are there any appliances or motors nearby?  As a kid, I remember the vacuum cleaner and the microwave causing this kind of interference while running, even if in the next room.

 

Second, did you make sure the solder joints didn't make connections that they weren't supposed to?  Did they bond well to both the board and the pins?  This is especially important around those large caps, since their primary purpose is to smooth the supply voltage.

 

A third possibility is a failing power supply.  If it's not giving you enough current, you'll still get ripple, which reads as noticeable AC voltage on DC supply lines.  That is, if you place your multimeter in AC mode and read the +5V to ground and see more than a millivolt or two, there may be a problem.



#9 Divarin OFFLINE  

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Posted Sat Apr 20, 2019 2:30 AM

hmm interesting. Well I've had this hooked up in two places. my home office to a CRT TV and my workshop in the basement to an LCD tv (where I took the video from), the behavior was the same in both places.  The power supply is brand new which I ordered from china: https://www.ebay.com...872.m2749.l2649

 

I've purchased these twice times in the past and haven't had any issues but to rule that out as the issue I do have another Atari in my living room which I use all the time (I'm fixing this one up to sell) so I guess I can try hooking this up there and see how that goes.

 

The solder connection on the caps you mentioned seem good with good continuity but one thing I noticed: Before soldering them on I tested running the board with and without the caps (after having pulled c241 I powered up the system, then held the replacement cap to the pads on the board to examine the change, not sure this was safe or not but was curious and willing to risk it) it was definitely fuzzier without the cap in place but it didn't seem to matter if I held on the old cap or the replacement both cleaned up the video a little (back to how it has been)

 

So then I soldered in the replacement c241 and did the same thing with c242 (which was located near the power plug for some reason and was a tiny cap looking a bit more like a resister)  When I did that there was no noticeable change in picture quality, the cap seemed to have no effect there so I'm thinking maybe a trace to this cap got damaged I'll look into that today.

 

I'll also look into measuring the voltage but I'm currently waiting for replacement multimeter probes to get shipped as I broke off one of mine and have been so far getting by by using the bare wire sticking out of the probe :(



#10 diablonet OFFLINE  

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Posted Sat Apr 20, 2019 10:55 AM

did you replaced the c241 and c242 for a new ones or used ones?



#11 Divarin OFFLINE  

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Posted Sat Apr 20, 2019 11:28 AM

one new and one old from another spare parts machine. the spare machine had good picture quality but strange joystick behavior.



#12 diablonet OFFLINE  

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Posted Tue Apr 23, 2019 9:10 AM

I own an atari 2600 with all caps replaced also with a composite mod, but it works fine in just 1 of my tvs, with all others I tried it looks like yours or totally black (no image), is the composite mod getting 5v?



#13 Divarin OFFLINE  

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Posted Wed Apr 24, 2019 4:03 AM

Hmm I didn't test the voltage on the composite mod since this behavior is unchanged from before I did the mod.  In fact the reason I decided to do the mod was because I suspected that the fault was in the RF modulator.  Since I haven't yet chucked this board into my "for parts" box I'll check out the voltage on the composite mod later today and let you know.



#14 Divarin OFFLINE  

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Posted Wed Apr 24, 2019 5:17 AM

Hmm interestingly I'm only getting 3.5v going to the composite mod, after leaving the unit on for a few minutes it went up to about 4.5 but I didn't notice any change in the fuzzy picture.

After a few powercycles I am now reading 5v, still fuzzy

Edited by Divarin, Wed Apr 24, 2019 5:41 AM.


#15 -^CrožBow^- OFFLINE  

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Posted Wed Apr 24, 2019 7:42 AM

I would replace the voltage regulator on the 2600 next. Put in a 1amp output variant like what is sold at Console5. In fact although you have replaced some components already, I order up console5's refresh kits for the 2600 and just replace everything in the 2600 with what is in the kit. I believe a new higher output VR is included in the kit.



#16 Osgeld OFFLINE  

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Posted Wed Apr 24, 2019 8:38 AM

Just cause no one has mentioned it check ground continuity from the tab of the voltage regulator to the end of the composite cable

#17 Divarin OFFLINE  

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Posted Wed Apr 24, 2019 1:04 PM

I've replaced the voltage regular once, but I do have another spare so I can try again. I am reading a steady 9 volts input and 5 volts output on the regulator right now.

There is continuity between the ground of the voltage regulator all the way to the end of the composite cable.



#18 ChildOfCv OFFLINE  

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Posted Wed Apr 24, 2019 1:48 PM

If the power is solid at the regulator but all over the place at the mod, that indicates either a power or grounding problem, as Osgeld suggested.  The power rails need to be solid all over the board, not just at the regulator.



#19 Divarin OFFLINE  

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Posted Thu Apr 25, 2019 3:37 AM

Agreed. It looks like my wonky power reading previously was due to the new multimeter probes not fitting tightly into my multimeter. After fixing that I went back and measured the voltage between the ground of the voltage regulator and the +5v going out to the composite mod circuit. It looks like a steady 5 volts (5.02-5.03)

#20 ChildOfCv OFFLINE  

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Posted Thu Apr 25, 2019 12:02 PM

That's better.  Did you happen to take an AC measurement of the power input, plugged into the Atari and turned on?  It should be very close to 0V.


Edited by ChildOfCv, Thu Apr 25, 2019 12:05 PM.


#21 Lohe OFFLINE  

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Posted Thu Apr 25, 2019 1:17 PM

I would also guess its a mass problem. I remember the same fuzzy picture with my RF Modul. Shortcutting from the body of the RF Module to the outer rf connector on the board elliminated all interferences as well as fuzzyness at me. And I guess AC current is at 0,1 at max. So there shouldnt be a problem. I dont know the av mod exatly, but if there is a video ground try to get anpther mass point. I soldered two wires to my outer metal (dont know the word) rf connector for example. Alls fine since then. Vader also. I think the vader may have some problems with mass at all. Perhaps dark energy or black hole matter ;-)

Edited by Lohe, Thu Apr 25, 2019 1:19 PM.


#22 Divarin OFFLINE  

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Posted Fri Apr 26, 2019 5:39 AM

Well I replaced the voltage regulator again since I had another one around. No change there. I did as you suggested, Lohe, and tried holding a ground wire between various ground points including the ground wire connected to the rca jack to the ground of the voltage regulator and also the rf modulator body and other various ground planes throughout the board. No change there.

There seems to be good continuity between all of the various grounds I tested, even between the voltage regulator and the ground of the rca jack.

I'm sure if I ordered every cap for the board and replaced every one there's a good chance it would work correctly but I think I'm going to use this as a parts board scavenging switches, the 3 chips, etc to work on other 2600's
I already have another one ready to be refurbished which seems to work fine except for a broken power switch.
I thought I might put this one on the back burner but knowing myself things put on the back burner tend to stay there and become clutter, plus I'd like to use that composite mod on this other 2600 and there's no practical way to revert this one back to rf.

Thanks for trying, everyone.

#23 Djoulz OFFLINE  

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Posted Fri Apr 26, 2019 1:24 PM

Hello,

 

I had exactly the same issue, and I did change everything on the MoBo without success ... And finally I try another power adaptor (the one I use was a brand new Amazon purchased just before the 2600), an old one that I had for years.

And guess what ! No more fuzzyness !! Perfect still image !

In fact I took a closer look at the power connector and it seems that in some case, the jack is shorter (half a milimeter) that could lead to bad contact ...

 

Well, it's worth give a try to this !



#24 Lohe OFFLINE  

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Posted Fri Apr 26, 2019 1:44 PM

Divarin, did you try to conmect the mass from the mod (I guess its one of the four cables) to another mass point also? Im still pretty sure there is a mass problem. But I may be wrong also. What summary is the measurement of possible AC-current about?

Interesting point by Djoulz. Never focussed myself on that, but will keep it in mind. Thanks for sharing!

#25 Djoulz OFFLINE  

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Posted Fri Apr 26, 2019 1:55 PM

Yes, the strange moving fuzziness on the screen, like ghost that reapeat with a sequence, moving down to up, was EXACTLY the issue I had !







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