Colecovision Console NO output

[Billbo1970]

Hello everyone,

 

I was on a day-trip last weekend and found a Colecovision at a thrift store. I took a gamble and bought it. It does not seem to turn on, nothing happens at all. The TV just says no signal. There don’t appear to be any lights anywhere to let you know the system is getting power? I have put a voltmeter to the power supply and get the correct readings. I also get the correct reading when putting the voltmeter to the motherboard. I get voltage under the power switch on the motherboard, but don't know what the correct numbers are supposed to be. I removed the power switch, gave it a thorough cleaning and used DeOxit as well. Re-soldered it, still no signal on the TV. Soldered wire to bridge the pins on the switch, making it permanently on to test it, still no joy. I have several cartridges but none of them make any difference. No Bios, no sound, just a black screens saying no signal. I am using an RF cable attached to a screw-on antenna connector. I have flipped the channel switch back & forth multiple times, same with the power switch. I've hit the reset button several times, held it down... nothing makes any difference.

 

Any suggestions? Thanks!

[Billbo1970]

I’ve made quite a bit of progress!  I now get the BIOS screen telling me to insert a cartridge. Plugging in a cartridge, the game appears to work.

 

NOW, I have an A/V issue. The TV makes a tick, tick tick sound, at roughly 1 second intervals. This coincides with two parallel white bars flashing their way down the TV screen.  I’ve tested the voltage at the VRAM and they read the proper GND, -5, +5, +12 and continuity is good between all the chips.  Any ideas on this one? Bad RF board? Playing with the 2 pots speeds up the ticking until the screen goes black. Playing with the other pot doesn’t appear to do anything at all.

[Billbo1970]

Here is a video showing what's going on now:

[overlord_manny]

Does the game ever boot? It almost looks like it's in a reset loop if not.

[Billbo1970]

On 10/18/2021 at 11:18 AM, overlord_manny said:

Does the game ever boot? It almost looks like it's in a reset loop if not.

Yes it boots into the games just fine, it's just the ticking and scrolling lines that are a problem... or I should say were... now I've screwed myself... ? 

 

I took off the daughter board under the RF shield, which required de-soldering it from the housing and also the green plastic riser pins. I didn't find anything amiss & put it back together... and I was back to a black screen with "No Signal" on the TV!! Aaargh!! ?  Checked all of my soldering, jiggled that area and now I'm NEARLY back to where I was… I have picture and sound again. Still the tick-tick-tick with the scrolling bar... but now everything has a green tint! I definitely screwed something up on that RF board to now make everything green. I'd bet that's where the other issue is coming from too, but nobody seems to be able to corroborate.

 

Any idea what I could have done to cause everything to be green? Most diagnoses for that say bad vid chip, but I wasn't anywhere near that part and screwing up the RF board somehow I'm sure could replicate such an issue, no?

[ChildOfCv]

Does it tick like that on other TVs?

 

The red/green signal is supposed to come to the daughter board on pin 3 of the riser.  Blue/yellow is on pin 7.  The B/W is on pin 6.  Make sure all of those are connected properly.  You may have lifted a trace while pulling the daughter board off.

Edited October 19, 2021 by ChildOfCv

[Billbo1970]

On 10/19/2021 at 7:43 PM, ChildOfCv said:

Does it tick like that on other TVs?

 

The red/green signal is supposed to come to the daughter board on pin 3 of the riser.  Blue/yellow is on pin 7.  The B/W is on pin 6.  Make sure all of those are connected properly.  You may have lifted a trace while pulling the daughter board off.

I don't have another TV to test it on, but it looked better before I messed with it LOL. I've been swamped with new inventory, I'll check that daughter board again when I have time.