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edburns

2600 Jr. AV Mod: audio but no video

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Hello fellow at Atarians. I tried my hand at installing the AV mod on my original Atari 2600 jr. After wiring everything up I observe that the video does not work. Has anyone here successfully done this mod?

 

Perhaps I could get some hand-holding in the form of a zoom or teams or Google meet session.

 

Attached is is a photo of the actual mod kit board I used.

 

I expect it is just crappy soldering on my part. But before I go and undo everything, I would like to have some reassurance that there isn't something else I've done wrong.

 

These are the specific Instructions I followed.

 

https://vintagegamingandmore.com/installation-guide-jr/

 

A little help?

 

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If you want help diagnosing the problem, we need to see photos of your soldering and general installation, not a quickly-panning video clip that barely shows your system.

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Absolutely! Thank you for your prompt response. I will post what I have, but I fear a synchronous Zoom or teams or Google meet session will be what I really need.

 

You cannot see the A3 next to the TIA, but I would think that's okay given that the audio is fine.

 

I have a multimeter, but I really don't know how to use it to diagnose the problem.

 

In any case thanks for anyone who replies to this.

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Hello everyone, given that my AV mod failed, I would like to buy a pre modded jr. Rather than just going on eBay, I would like to ask here. Does anyone have a recommendation for how to buy a pre modded 2600 Jr that would benefit our community?

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Might be more cost effective to send your current jr to another to look it over who might be able to get it going for you cheaper? Did you already install and wire in the AV output jacks?

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49 minutes ago, -^CrossBow^- said:

Might be more cost effective to send your current jr to another to look it over who might be able to get it going for you cheaper? Did you already install and wire in the AV output jacks?

That would be ideal.  Yes, I am at the step where you are supposed to adjust the pot, but because the video doesn't work I can't perform that step.  I would love to be able to send it to someone to take a look.  I'm attached to this hardware as it's the same unit I had from childhood.   As I showed in the YouTube at the top of the thread, the audio works, and there *is* a video signal.

 

Do you have a recommendation for such a person?  I was willing to spend $60 on an auction (but was outbid), so that gives a pricepoint.

 

Thanks?

 

Ed

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So..in looking at the instructions you provided I think I see the issue. Your red wire which I believe is your +5v into the mod board is in the wrong via off of where you removed the Q4 transistor. You need to attach that wire to the other location near the inductor (Square can). I've circled it in this modified pic of yours. Or at least it looks like you have the +5 attached to the wrong location. Might also verify the other connections are making good contact as well as those appear to be in the right spots but wouldn't hurt to make sure.

 

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I meant to come back to this post and reply further but I forgot.  I think @-^CrossBow^- is onto something.


Also, the video shows that you have audio and SOME kind of video signal, but the sync is all messed up. I’m not familiar with these inexpensive a/v mods (my systems all have UAVs in them), but speaking generally the NTSC sync signal is provided on the Luma channel of the video signal output. I’d have to dig up Jr. schematics and puzzle out the wiring to be sure, and then try to grok the simple a/v mod circuit, but your TV is certainly not getting a good sync signal on the video. That much is clear. 

 

 

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2 minutes ago, DrVenkman said:

I meant to come back to this post and reply further but I forgot.  I think @-^CrossBow^- is onto something.


Also, the video shows that you have audio and SOME kind of video signal, but the sync is all messed up. I’m not familiar with these inexpensive a/v mods (my systems all have UAVs in them), but speaking generally the NTSC sync signal is provided on the Luma channel of the video signal output. I’d have to dig up Jr. schematics and puzzle out the wiring to be sure, and then try to grok the simple a/v mod circuit, but your TV is certainly not getting a good sync signal on the video. That much is clear. 

Those simple AV mods simply tap from the video input to the RF modulator.  So it should be a complete signal including color.

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2 minutes ago, ChildOfCv said:

Those simple AV mods simply tap from the video input to the RF modulator.  So it should be a complete signal including color.

In that case it might just be as simple as the +5V line, then.

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2 hours ago, DrVenkman said:

In that case it might just be as simple as the +5V line, then.

Yeah. this mod is just an amp for the composite already going into the modulator. Pretty sure the issue is that the +5 the tranny needs isn't present so not really able to amplify the signal for the TV to fully see in this case. And I can't see the traces, but it doesn't look like there is anything in place here for the audio and is just a straight through on that? I don't see a cap or anything for any additional filtering and to me in his video the audio seemed a bit hot? But maybe that is just me?

 

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On 6/3/2020 at 2:26 PM, DrVenkman said:

I meant to come back to this post and reply further but I forgot.  I think @-^CrossBow^- is onto something.


Also, the video shows that you have audio and SOME kind of video signal, but the sync is all messed up. I’m not familiar with these inexpensive a/v mods (my systems all have UAVs in them), but speaking generally the NTSC sync signal is provided on the Luma channel of the video signal output. I’d have to dig up Jr. schematics and puzzle out the wiring to be sure, and then try to grok the simple a/v mod circuit, but your TV is certainly not getting a good sync signal on the video. That much is clear. 

 

 

Thanks for the thoughts.  I will move the red wire from the collector to the emitter and report back.

 

I had never heard of a UAV before. But I found this excellent video here. 

 

 

As this is my first attempt at modding, I am glad to see the endorsement in the video of choosing a cheap simple mod first. If I am able to get this going, maybe I will get another system and try the UAV mod with it.

 

Thank you so much for coming along for the ride.

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Gentlemen, thanks for your help. It works now! You made my day!

 

Ed

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Excellent! Glad we were able to point you into the right direction. I've not actually done this simple composite mod myself as I always use my 7800 for both 2600/7800 gaming needs but again, glad it was something easy to fix in this case.

 

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