5200 with no sound and bad joystick keypads

[jwbeck17]

Hi everyone, this is my first post as I just got my hands on my old 2-port 5200. I got it cleaned up and running, however I have run into a few snags...

 

First, the sound feed is gone. I can hear the familiar buzz that these machines create, however no game sounds. cleaned the unit inside and out and replaced the switchbox with an F to Coax connector but no luck, although the video got noticibly better.

 

Second, several of the keypad buttons do not work, specifically the lower row. I found the instructions on how to open up and clean these which I did, however it didn't seem to help too much, as the buttons are not functioning. Some of the upper ones are this way as well.

 

Any suggestions on how to narrow down the exact issues and figure out how to fix them? I've never done soldering or anything of that nature, but I am somewhat of a DIY guy, so I'd love your suggestions on these fixes.

 

Thanks!

[ApolloBoy]

Well, as for your first issue, I would try replacing the POKEY chip. As for your second issue, you're gonna have to rebuild your controller, I would suggest going here for replacement parts.

[Rybags]

If the POKEY chip was a dud, then the controllers wouldn't work at all.

 

Sounds more like a bad solder joint or broken trace, or possibly an RF modulator problem.

 

Best bet is to do an A/V mod, which might fix the problem, but at the very least will improve the video quality even more.

[JB]

Isn't POKEY responsible for reading the keypad, too?

 

IF you ahve no sound and select dead buttons after cleaning, a wounded POKEY sounds like a good culprit.

[Rybags]

POKEY does keys and joystick on the 5200.

 

No mention in the first post of whether his joysticks are dead though.

[jwbeck17]

Thanks for your recommendations. As for the joysticks, they still work somewhat. The stick portion works fine and the upper and some of the lower buttons work fine. I did read that the POKEY chip may be the culprit since it affects both the sound and keypad, but I'm not sure how best to troubleshoot to confirm. I haven't tested both handsets on both ports to see if the exact same buttons are the problem, but that is the last way I can think of to confirm the issue.

 

As for the POKEY chip: Please forgive my lack of knowledge, but where is this chip located on the board? How is this replaced?

 

Thanks!

[Bruce Tomlin]

As for the POKEY chip: Please forgive my lack of knowledge, but where is this chip located on the board?  How is this replaced?

http://en.wikipedia.org/wiki/POKEY

 

Also, if a single joystick port doesn't work, it's going to be a problem with one of the 4052 chips. There is a line of about five of them in a 4-port unit, and the leftmost one is for port 1.

 

Another possiblity is a problem with the RF modulator, as someone mentioned in a thread about a Colecovision with bad sound.