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Tidus79001

ColecoVision - no audio, only static even while playing games

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I recently purchased a untested ColecVision on eBay and the console is working, but there is no audio at all and the static noise is still playing from the PC TV speakers after the console is turned on. Picture and everything else works without issue. I have tried the following so far:

 

- Connected to a CRT using a RF adapter on the coax input

- Tried another RF adapter and cable, but still have the same issue

- Tested on both channels 3 and 4

- Issue is present with all games

- No audio at all (no sound effects heard competing simultaneously with the static)

 

Any ideas what is going on here, and how to resolve it. Is it likely that this console was an AV mod attempt gone wrong and that the seller is dishonest and was offloading it on a unsuspecting buyer who bought the console in good faith as being untested?

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I had a similar issue with a ColecoVision once that was resolved by opening up the top of the RF box inside the console and tuning one of the pots inside with an Allen wrench. Might be worth a shot..

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Yeah, the audio modulator is definitely off kilter. If you're lucky, it's just a matter of re-tuning the coil in the corner by the channel switch.

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First try adjusting the pots in the rf box (see picture below). There are two pots, one is for video, and the other is for audio. If that doesn't work, your only other option is to do an AV mod. It is not worth it to try to fix the rf modulator, because it is too complicated and not worth the time. If you do an AV mod (and follow the directions that come with it), and still have no sound, then you need to get the sound directly from pin 7 of the sound chip. Ben Heck has instructions for that. https://www.benheck.com/bens-colecovision-composite-video-mod/

Most of the time the problem is with the rf box, and can be fixed with an av mod. If the problem is with the sound chip, then the AV mod won't fix the problem, but usually the sound chip is not the problem.

mod1.jpg

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First try adjusting the pots in the rf box (see picture below). There are two pots, one is for video, and the other is for audio. If that doesn't work, your only other option is to do an AV mod. It is not worth it to try to fix the rf modulator, because it is too complicated and not worth the time. If you do an AV mod (and follow the directions that come with it), and still have no sound, then you need to get the sound directly from pin 7 of the sound chip. Ben Heck has instructions for that. https://www.benheck.com/bens-colecovision-composite-video-mod/

Most of the time the problem is with the rf box, and can be fixed with an av mod. If the problem is with the sound chip, then the AV mod won't fix the problem, but usually the sound chip is not the problem.

 

mod1.jpg

Oops, I guess I shouldn't just assume you're NTSC.

 

But assuming that's the case: If you have perfect picture, do NOT adjust the RF coil. That is the coil used in final modulation to a TV channel once all of the various signals have been created and mixed together (luma, chroma, FM sound). Adjusting that will just remove what you do have.

 

The variable transformer in the upper right of this picture is the only one you should touch for a sound problem.

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If the rf is screwed you can not av mod. Trust me I tried. You will get a black screen. The av mod board does very little after the rf. Only way is f18a. I tried repairing my rf I replaced the chips on it and no avail. Did this after replacing the vram. Good parts coleco.

Edited by Jinks

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I can't comment on PAL or SECAM as I've never seen the schematics for either of those versions. But on NTSC, if you have good picture on the RF, with or without sound, you can do the AV mod.

 

Of course the next alternative to waiting in the F18A queue is to get or build the RGB mod that someone (Ben Heck maybe?) came up with, and run it to the component video.

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The old AV mods for the ColecoVision improperly draw sound and you will get low volume output with the Opcode SGM and Exp. Mod. #1 Atari Adapter. You should draw sound for AV mods from the Cap at C88.... I think the left leg of the CAP if I recall correctly.

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On 1/16/2019 at 1:45 PM, Tidus79001 said:

I recently purchased a untested ColecVision on eBay and the console is working, but there is no audio at all and the static noise is still playing from the PC TV speakers after the console is turned on. Picture and everything else works without issue. I have tried the following so far:

 

- Connected to a CRT using a RF adapter on the coax input

- Tried another RF adapter and cable, but still have the same issue

- Tested on both channels 3 and 4

- Issue is present with all games

- No audio at all (no sound effects heard competing simultaneously with the static)

 

Any ideas what is going on here, and how to resolve it. Is it likely that this console was an AV mod attempt gone wrong and that the seller is dishonest and was offloading it on a unsuspecting buyer who bought the console in good faith as being untested?

 

On 1/16/2019 at 3:49 PM, ChildOfCv said:

Yeah, the audio modulator is definitely off kilter. If you're lucky, it's just a matter of re-tuning the coil in the corner by the channel switch.

Tuning the RF coil didn't resolve the issue.  Is there anyone here who I can pay to perform the AV?  I don't feel comfortable doing the mod myself.

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33 minutes ago, Tidus79001 said:

 

Tuning the RF coil didn't resolve the issue.  Is there anyone here who I can pay to perform the AV?  I don't feel comfortable doing the mod myself.

@Tidus79001, Where are you located roughly?

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Just reviving this thread because I also have a CV with video but no audio. I found this reddit thread that describes the issue I have. I've tried adjusting the pot and that did nothing, but if I press down on the RF board as described in that thread I can occasionally get sound back. Any ideas about what the issue might be? I'm no electronics expert but I can do basic soldering. Any help would be appreciated!

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So you're getting no sound at all, not even static?  If you can get sound back by pressing on the board, the most likely culprit is a broken solder joint or trace.  Try reflowing all of the connections on the RF board.  It's a 1-sided board, so there are no traces on the inside part.

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Ah ok that's good to know, I was wondering whether I was going to have to get to the underside of the board. To reflow all the connections should I just go one by one reheating up all the solder points on the RF board basically? And thanks for the reply!

Edited by amn

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6 hours ago, amn said:

Ah ok that's good to know, I was wondering whether I was going to have to get to the underside of the board. To reflow all the connections should I just go one by one reheating up all the solder points on the RF board basically? And thanks for the reply!

Yeah that's the best way to do it.  Be methodical to make sure you don't miss one.

 

Also, I see that the title says 'only static'.  Maybe I missed that at first?  Or did you change the title?  If you get static, that means the audio modulation is not working.  In some ways that's better because it almost guarantees that the problem is on the RF board, where "no sound" could be in multiple places.

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7 hours ago, ChildOfCv said:

Yeah that's the best way to do it.  Be methodical to make sure you don't miss one.

 

Also, I see that the title says 'only static'.  Maybe I missed that at first?  Or did you change the title?  If you get static, that means the audio modulation is not working.  In some ways that's better because it almost guarantees that the problem is on the RF board, where "no sound" could be in multiple places.

Yeah no sorry I don't have any static whatsoever unless I play around with the pot. Otherwise it's completely silent until I put pressure on the board which then snaps the audio in perfectly.

 

Thanks for the help with this. I should be able to get around to it this weekend. I'll be sure to report back the results here!

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Finally got around to reflowing all the connections on the RF board this morning and it worked! I can't believe it! Now I've got 2 working CVs and one to go once that RAM replacement kit arrives! This one's going to a friend of mine who grew up with the CV but hasn't played it since.

 

Thanks again guys for all the help I really appreciate it.

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