Fire Buttons On Port 1 of Colecovision not working!

[evilgonzo]

Hey Guys ... I was hoping I might be able to get some info on this. Here's the issue , The fire buttons on port 1 on my Colecovision dont work. I tried switching controllers to see if if that was the problem and no luck. Fire buttons still wouldn't work. So I tried the same controllers on Port 2 and no issues. So do you guys think something might need to be cleaned or maybe a SN74LS541N chip needs to be replaced? Thanxs

[Gemini]

One quick thing you should test is wiggling the plug while holding the fire button. If it responds while you're doing that then it may be just a dirty contact, or less possibly a loose wire inside the console as a result of a broken soder connection. For some reason, I have a similar problem with my pair of Atari 2600 paddles. If I plug them in straight, they may or may not work, but if I wiggle the plug very slightly to the left they work perfectly. It doesn't happen with the joysticks so in my case I'm pretty sure it's just the contacts inside the plug itself.

 

I don't actually own a Colecovision so that's just guesswork, but I thought I'd make mention just in case it helps any. ^_^;

Edited February 23, 2008 by Gemini

[evilgonzo]

GEMINI ... I gave that a try like you suggested and unfortunaly it was a no go. I tried giving the pins on the Coleco a cleaning as well with no luck. Thanks for trying though.

[Bruce Tomlin]

It's almost certainly the 74LS541 chip. That is the only case I have ever heard of where a TTL chip regularly gets zapped.

 

J5 -> U19

J6 -> U18

 

You will certainly want to clip the pins of the chip before desoldering, and install a socket. Also, it wouldn't hurt to buy an extra chip.

 

Here are some hints about desoldering: http://xi6.com/hacks/desolder.html

[evilgonzo]

Thanks for the heads up on that Bruce. Luckily i've had some experience replacing some chips when i had a couple go out in my Commodore 64. I also find that adding a socket onto the board makes it way easier to change the chip in the future if need be. I found a nice board layout if anyone needs one .. http://www.atarihq.com/danb/files/colecovision.pdf .. I got a local electronic shop that tends to carry lots of obscure chips. So hopefully locating one , won't be much of a hassle .. cringe to think I may have to buy one online .. you usually have to buy a lot. So lets hope it doesnt come to that.