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5200 RFMOD removed no longer powers up


SwampFox56
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I recently bought an Atari 5200 S-Video modkit.

 

 

When I first installed it (I chose to lift the pins of the GTIA) I tested it, and it worked great. So what I did after that was; I wanted to mount my A/V jacks on the side of plastic case where the RF modulator sits. Since it’s no longer in use, I opted to remove it.

 

So I removed the RF modulator, and I changed the LED color and now I get nothing. The system turns on (or the LED does at least), but I get no video output from S-Video or Composite. Is there any advice anyone can give me?

 

Also, I should note that I ran continuity checks on the GTIA (to ground) to see if any of the pins had shorted. Only pin 3 had continuity with ground. That leads me to believe that the chip itself is okay. (I should also note that I always where ESD protective gear (as in an antistatic wrist strap).

 

I’m grabbing 5 volts directly from one of the 7805’s, and I checked to make sure the 5200 S-Video board was getting that voltage. It was.

 

So I’m at my wits end here. Can you give me any advice?

 

 

EDIT: I just found out that the 7805 that sits CLOSEST to the A/C jack is only outputting 0.30 volts. It's also receiving only 0.6 volts on the input rail. So I'm now all but certain this is the problem. Does the RF Modulator clamp the rest of the system to 5volts?

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I should have mentioned the type. It's a 2-port system.

 

Ok. Check for the voltage where pin 3 of the rf mod was. You might not have enough draw to trigger the "flip/flop" IC the power switch activates. That IC near the switch splits the power into the two circuits: video and logic.

2-ports are more prone to failures at this location for some reason

Edited by zylon
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Ok. Check for the voltage where pin 3 of the rf mod was. You might not have enough draw to trigger the "flip/flop" IC the power switch activates. That IC near the switch splits the power into the two circuits: video and logic.

2-ports are more prone to failures at this location for some reason

 

On pin 3 of where the RF mod used to be - I'm getting 5 volts. Should I be getting nothing? All I know for sure is that the secondary 7805 is not turning on (I can confirm this by testing the pins, and the fact that it's producing no heat whatsoever). Anyways, I just tried replacing that 7805... no dice.

 

The problem sounds like it's with the flip-flopper like you said.

Edited by SwampFox56
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You could always try soldering in the rf mod just enough to test and see. I do not believe the system is daisy-chained.

 

So I tried soldering the 5 pins of the RF modulator back in place. Again... no luck. Which I'm actually glad about because I want the RF modulator gone.

 

With that being said, I just ran continuity checks on all of the pins on the CD4013BE (Flip-Flopper) and nearly all of them were shorted to ground. In fact, touching two of the 12 pins actually caused the system to turn on. I'm not sure how that vhip was fried, but it definitely is. I'm gonna have to order a replacement and report back.

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It could've been zapped by a static discharge when you were desoldering the RF modulator.

 

I have no doubt that it was ESD that killed the chip. But I was wearing antistatic protection. I just don't see how that would be possible (unless the RF Modulator generates it's own static electricity?? Which sounds incredibly unlikely to me...

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I have no doubt that it was ESD that killed the chip. But I was wearing antistatic protection. I just don't see how that would be possible (unless the RF Modulator generates it's own static electricity?? Which sounds incredibly unlikely to me...

Is your desoldering equipment ESD safe?

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Is your desoldering equipment ESD safe?

 

All I use is standard solder sucker. Plastic tip, metal spring inside. My soldering iron is rubber/plastic until (obviously) the metal.

 

In theory I guess it's possible that the solder sucker is generating static electricity when the spring rubs along the side of the sucker when you push it down. For reference, I've always used these (because they're cheap). If the ladder is true - wouldn't any electrical charge discharge through my hand since I'm a path to ground?

Edited by SwampFox56
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  • 3 weeks later...

To wrap this up - I confirmed the problem was the CD4013 Flip-Flopper. I got a lot of 10 off eBay and just stuck one on top of the existing, broken CD4013. That worked fine so rather than desoldering the old CD4013 out of my 5200, I just soldered the new one on top of the old one. Everything works great now.

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A better way would have been to cut out the old 4013, desolder the loose legs and then install a socket. If that 4013 goes bad again it's gonna be harder to replace, so having a socket will save you a lot of trouble down the line.

 

If this was someone else's console, I would have. But I don't have any sockets on hand (nor have I found a website that sell them cheap) and even if the new Flip-Flopper goes bad on me (which doesn't seem likely as the existing CD4013 was fine for over 30 years) I can still cut out the two CD4013's with my side-cutters.

 

With that being said - if this flip-flopper was being used in a logic circuit, I would have definitely gotten rid of the old one - but all it's doing is powering the console. So I fail to see any problem. Also - I've come to the conclusion that the solder suckers I've been using aren't ESD friendly and I'm waiting for a couple of new ones to show up...

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If this was someone else's console, I would have. But I don't have any sockets on hand (nor have I found a website that sell them cheap) and even if the new Flip-Flopper goes bad on me (which doesn't seem likely as the existing CD4013 was fine for over 30 years) I can still cut out the two CD4013's with my side-cutters.

I consider 13 cents to be pretty cheap: http://www.jameco.com/1/1/198-14lp-pin-single-wipe-low-profile-ic-socket-0-3-inch-wide.html.

I like using the machined pin sockets myself which are considerably more expensive at 65 cents: http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_37197_-1

 

Note that they do have a minimum order charge, but I usually don't have any trouble meeting it:

"Because Jameco incurs a significant cost to process every order, we charge $5 on any order less than $10."

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