Atari 2600 Audio Video Problem

[electromaster_84]

First I know the picture quality isn't great, but it's really hard to capture the problem on camera from a crt television. My console is a composite modded 4-switch vader. The mod I used is a simple transistor and 2 resistor type ordered from Vintage Gaming and More (http://www.vintagegamingandmore.com/product/atari-video-mod-kit/) The kit was easy to install, and everything seemed to go well. The video quality isn't the best, but it's good enough for me.

 

Anyway on to the problem I've been having. If you look near the center of the screen in the pictures you will notice some type of small lines or static. The lines/static only appear when a sound is played, and it seems the higher the pitch of the sound the more noticeable it is. I've done some testing and I'll just list my findings along with the parts I've removed from the motherboard below.

 

Parts Removed From Motherboard

1) RF Module

2) Q201

3) R209

4) L201 (Audio Coil/Inductor)

 

 

Testing Steps Result

1) Removed RCA audio cables from jacks on atari to tv No audio, but lines still appeared

2) Replaced capacitors C214,C201,C241,and C243 No change lines still appeared

3) Desoldered Audio wire from mod board to R206 No audio, but also no lines

 

I haven't tried replacing the two audio capacitors C206 and C207 because I don't have any suitable replacements on hand.

 

Edited April 25, 2016 by electromaster_84

[electromaster_84]

Anybody got any idea as to what is causing this?

[rednakes1]

Did you ever manage to fix this issue? I see the same problem on my 4-switch woody with the same mod kit you used, when playing Ms. Pacman. When sound plays or when a new turn begins, a white or faint vertical line flickers down the middle of the screen.

 

EDIT: Maybe you can try this, put a 1uF capacitor before you grab the audio from R206 (I haven't tried this):

 

http://atariage.com/forums/topic/139777-simple-2600-audio-mod/?p=1690158

Edited November 3, 2016 by rednakes1

[electromaster_84]

First I would like to apologize if this is considered thread necromancy, but I have finally found a solution to this problem! I would like to thank rednakes1 for his suggestion to add a 1uf capacitor to the audio line. Adding the capacitor had zero effect on the problem, but did get me thinking back to my initial testing. When the audio was disconnected from the mod board no vertical lines appeared when a sound should have been played. I couldn't hear if a sound had been played of course because the audio was disconnected. I just wasn't thinking straight or was frustrated with the whole mess back then, so I reconnected everything and lived with it. Until today that is when inspiration struck me! What if the audio circuit of the mod board itself was causing the interference? Could it be so simple as to just bypass the audio around the mod board completely? Well I'm here to tell you it is, and why I didn't think of it sooner boggles the mind. So today I soldered a short length of wire from R206 to the positive terminal of a 1uf capacitor, and soldered another length of wire from the negative terminal of the capacitor to the audio jack. Boom presto I had glorious audio, and no interference or vertical lines marring the picture.

 

TLDR

Disconnect the audio from the mod board. Then connect the positive terminal of a 1uf capacitor to R206, and the negative terminal to the audio jack with some wire.

[0078265317]

Nice thanks for sharing.

[AtariLeaf]

First I would like to apologize if this is considered thread necromancy, but I have finally found a solution to this problem! I would like to thank rednakes1 for his suggestion to add a 1uf capacitor to the audio line. Adding the capacitor had zero effect on the problem, but did get me thinking back to my initial testing. When the audio was disconnected from the mod board no vertical lines appeared when a sound should have been played. I couldn't hear if a sound had been played of course because the audio was disconnected. I just wasn't thinking straight or was frustrated with the whole mess back then, so I reconnected everything and lived with it. Until today that is when inspiration struck me! What if the audio circuit of the mod board itself was causing the interference? Could it be so simple as to just bypass the audio around the mod board completely? Well I'm here to tell you it is, and why I didn't think of it sooner boggles the mind. So today I soldered a short length of wire from R206 to the positive terminal of a 1uf capacitor, and soldered another length of wire from the negative terminal of the capacitor to the audio jack. Boom presto I had glorious audio, and no interference or vertical lines marring the picture.

 

TLDR

Disconnect the audio from the mod board. Then connect the positive terminal of a 1uf capacitor to R206, and the negative terminal to the audio jack with some wire.

 

Big bump - I was playing some Ms Pacman on my Vader modded with the exact same mod the OP used and I noticed this line in the middle during certain gameplay elements like ms pacman dying or restarting a life. I'll have to try this. I'm sure I have a few 1uf caps kicking around that I bought from console 5 a while back. Good to know and thanks for posting this fix. I'm guessing the audio portion of the mod isn't even necessary then if you can go straight from R206 to the audio out jack with only a 1uf cap in between.

 

Quick question, this would be a ceramic 1uf cap correct? Like this - https://console5.com/store/1uf-10-50v-multilayer-ceramic-capacitor-mlcc-axial-leads.html

Edited November 28, 2018 by AtariLeaf

[electromaster_84]

Sorry for not replying sooner, and I hope you have resolved the issue by now. To answer your question, since the last time I posted I have removed the capacitor from the audio line of my console with no ill effects. I found it made the audio a bit harsh, and since the mod board just passed the audio straight through I figured it wasn't needed. After tinkering with my console for awhile I've found the best solution to this problem is to route the audio wire away from the video wire of the mod board. In my opinion this problem stems from using the unshielded solid core wire provided in the mod kit causing interference between the audio and video signals. If I were to install this kit again I would use some kind of shielded av cable instead of the wire provided.

[AtariLeaf]

Interesting. So don't bother with the 1uf cap? I hadn't done anything yet because I thought I had one on hand but they are only .1uf. I'd gone back to using my rf junior unit for the time being.

 

So now you're just running a wire straight from the resistor to the audio jacks? And you keep the audio wire physically as far away from the mod board and video wires as possible because the interference is caused by the audio and video wire being in close proximity to each other? Interesting. If I don't have to bother with the 1uf I'll just make the changes this weekend. I want to change out a 2200uf cap and the chicklet cap on this unit anyway thanks

Edited December 27, 2018 by AtariLeaf

[AtariLeaf]

BTW, I wonder if this is a 4switch/Vader issue. Everyone I see who's had interference issues with av mods seems to be with these models IIRC. I have interference issues with homebrews on this same console, aside from the issue in this thread. I should try modding a light sixer and see if the same thing happens.