Colecovision tech help

[y-bot]

Hi, I have a Colecovision that needs some help. Even without a cartridge in it the warning that displays on the TV has a problem. Some of the letters have green boxes over them. I tried the power supply with another Colecovision and it works. I know some people here have replaced the on/off switch but I don't think that is the problem either. I had it apart last night and was curios to know if the console should work without the metal shield. I know there is a piece of braided wire soldered to the top shield that I assume is a ground. I couldn't get anything to the TV except black screen even if I touched the braided wire to the top metal shield. I also had the top of off the RF box. What are the two screw pots in the RF box for? Any help would be greatly appreciated.
Thanks, Y-bot

[CrazyImpmon]

Are you really sure the switch is not the problem? Because if the switch has been ruled out, the most likely cause is a blown RAM chip. CV is quite touchy and easily blows out a chip or 2 simply by touching the joystick pin or something.

The 2 screws you mentioned are for adjusting frequencies. Changing that won't fix the scrambled picture, it would only result in snowy picture or noisy sound.

[omnedon]

Sounds like a switch issue to me. Garbled graphics are one of the early signs, and all but one of the eight CV's I've seen recently have needed the switch fix. It's inevitible if the CV gets used regularly.

Any staticky noise when powered on? Does flipping the switch "fast" or "slow" change the result? Try downward force on the switch when activating. If any of those things change the output result, your switch needs replacing. It's a pain in the ass, but once done, only dirty carts cause graphical glitches.

Ratshack sells a similar switch. I can go find the number.

[y-bot]

Maybe it is the switch. I thought it would not work at all if the switch was bad. Is it just a matter of the contacts in the switch being dirty or something else? I will do some more testing. Thanks for the help guys.

Y-bot

[Zaxxon]

I'd just try the CV with another CV power supply. Every CV I've had that had problems were fixed by just trying different PS's with it. There are NOS ones on Ebay.

[y-bot]

I have extra power supplies. I tried the one I am using on another Colecovision and it worked fine. I should re-check it though.
Thanks, Y-bot

[y-bot]

OK, so I did some more testing. I tested the power supply I have been using for this Colecovision I'm working on and it works fine with the CV in my collection. I put the broken CV back together and I also took the on/off switch apart and cleaned the contacts. Here's what happens now. With the power supply I have been using I get a black screen and with the one from my collection I get the green boxes around some of the letters on the warning screen like I was getting before. Wiggling or pushing the switch does nothing but turning it off a little bit produces different patterns on the TV. Does it sound like the switch is bad or something else?

Thanks, y-bot

[zektor]

When you cleaned the unit did you pop off the cover to the rf modular and blow it out with compressed air? This sometimes helps. The cover will just come off with a little effort.

[Zaxxon]

I'd try a 3rd PS before opening it up!! They're all a little bit different. I've never needed to replace a power switch on a CV. That's more of a 2600 problem.

[y-bot]

Ya I was thinking of trying a 3rd PS. I have another one somewhere I just need to find it. It seems like they are just very finicky when it comes to power requirement. I guess that's why the on/off switch can be a problem. I need to get some compressed air and electrical cleaner and give the RF a good cleaning. Luckily I already have a Colecovision in my collection and this one I'm working on is an extra.
Thanks again for the help!

y-bot

[omnedon]

My opinion, it's the switch. I've never successfully repaired a stck CV switch. Once taken apart, the orig switch never works for me.

http://www.radioshack.ca/estore/category.aspx?language=en-CA&pagenum=5&category=Switches+Switches&catalog=RadioShack

275-403

Getting it to play nice with the external black glamour cap is tricky, and it's posts will need to be filed down some. Make sure none of the board surface contacts come off, or you'll end up making a bridge. I had to on mine.

You may want to consider multimeter testing your PS's. The outputs are clearly marked on the PS label.

[y-bot]

I replaced the switch today and it didn't fix the problem. I blew out the RF box and that didn't do anything either. I put the old switch back in it and put it away for now. I give up for now anyway. Thanks for all the help though!

Y-bot

[FABombjoy]

Another hint for stubborn power switches:

If the power switch operates fine with the switch cover & system case removed, but is damn tough to slide back and forth once you put the switch cover & case on, pack some paper towel up into the switch cover, so that it stands a little bit higher off the power switch (about 2mm or so). Once you put the system cover back on, the extra tension on the power switch from the switch cover being pressed against the system case makes the internal switch contacts stop jamming up.

The above paragraph may make more sense if you have a disassembled Colecovision in front of you.

[omnedon]

It does it even without a cart inserted eh?

The CV FAQ mentions trying hard wiring the power supply to the baird for improved connection. I've never had to do it... but if your running out of ideas.

My guess is somewhere along the way, it's not getting quite enough power. I've seen PS's as out as 0.2 v causing a CV to spit garbled graphics.