Again on Colecovision garbled graphics problem.

[highinfidelity]

Ten years ago or so it was common belief that a Colecovision displaying graphic garbage at startup needed to have its ON/OFF switch contacts cleaned. It didn't make much sense, but I did it nonetheless as it was suggested by many, I damaged the case and the stickers while doing so, and the problem seemed indeed to be gone for one reason or another.

 

During Christmas I plugged in again my Colecovision after a long time in storage, and the garbled graphics are there again, but I'm definitely no longer persuaded that the ON/OFF switch has anything to do with it. If I just let it turned on for few minutes, after this "warm up" time the garbage is gone, which makes me think that there is some component that is out of tolerance but performs "well enough" after some warm-up time. Perhaps a capacitor or a resistor, or the whole power supply, who knows?

 

Has anything new been written about this well known problem in the last years?

[ChildOfCv]

Contacts can oxidize from disuse.  It's possible that if the problem is a long period of disuse, you could just cycle the switch a few times to scrape off the junk.

 

But you're also correct that confirming the problem before "fixing" it can be beneficial.  When you get garbage on turn-on, check the voltages of each of those huge chokes next to the switch.  One should be +5 and the other should be +12.  Both come from the switch.  If either are low, then you can be pretty sure the problem is the switch.

 

Also, make sure you don't short any components when taking measurements.

Edited January 7, 2020 by ChildOfCv

[Charlie_]

Mine acted just the same way. I replaced the power switch. Seemed good for a bit. Then it started again. So I got that USB power supply solution from Germany and it has been good since. 

[highinfidelity]

Well, thanks. I suspected since the beginning that all that work to have the switch disassembled (and the case and stickers damaged while on the task...) was completely useless, internet garbage copied and pasted over and over. Will check the power supply unit. I think a good test would be to let the power supply alone pre-heat, and then turn on the cold Colecovision and see what happens.

[dkml]

I think I need to look at that USB power device.  I recently got a power supply replacement for my Colecovision via Ebay and it looked great but then the screen gradually turned white even though I could hear all of the sounds of the game.  I'm guessing this is the fault of the power supply but has anybody ever heard of that happening?  I usually just see comments about visual garbling or part black and white screens.