Need some help with problematic Colecovision Please

[Tony Montana]

Hi all,

 

I recently bought a CV off ebay, sold as spares or repairs.

 

I have opened it up and checked it over with the multi meter.

 

Getting power into the system fine and the power switch seems to be working also, checked this with multi meter also.

 

The console seems to be powering up OK but i am getting no output to the TV

 

It's as if it not connected to the TV at all.

 

On my other (working) CV, when i turn it on, even when not on the correct TV channel, the static on screen will jump. But with this non working one, there is nothing.

 

I am in the UK and the non working CV is a USA model. As far as i understand, even if my TV doesn't support NTSC i should still get a picture on screen, albeit black & white.

 

Can anyone shed some light on what might be at fault or any suggestions on what to check next ?

 

thankyou.

 

P.S. The motherboard looks in pretty bad shape, with quite a lot of corrosion. Also there is a suspect wire soldered to one of the pins on the expansion port that leads to a point on the mobo, then continues on the reverse side (see pics). Is this normal or a mod someone has done ?

 

Sorry for the long winded post, just trying to give as much info as possible.

 

Thanks again

[mimo]

Hi all,

 

I recently bought a CV off ebay, sold as spares or repairs.

 

I have opened it up and checked it over with the multi meter.

 

Getting power into the system fine and the power switch seems to be working also, checked this with multi meter also.

 

The console seems to be powering up OK but i am getting no output to the TV

 

It's as if it not connected to the TV at all.

 

On my other (working) CV, when i turn it on, even when not on the correct TV channel, the static on screen will jump. But with this non working one, there is nothing.

 

I am in the UK and the non working CV is a USA model. As far as i understand, even if my TV doesn't support NTSC i should still get a picture on screen, albeit black & white.

 

Can anyone shed some light on what might be at fault or any suggestions on what to check next ?

 

thankyou.

 

P.S. The motherboard looks in pretty bad shape, with quite a lot of corrosion. Also there is a suspect wire soldered to one of the pins on the expansion port that leads to a point on the mobo, then continues on the reverse side (see pics). Is this normal or a mod someone has done ?

 

Sorry for the long winded post, just trying to give as much info as possible.

 

Thanks again

I doubt very much if you will get a picture via RF output,PAL televisions in the main do not go down as low as the frequencies needed for NTSC. you may get something via AV, but you would have to mod the Coleco first.I have had to mod all of my NTSC stuff to work in the UK

You may be able to get an NTSC signal via a Video Recorder, but you would have to check the spec.

Good luck, it does look very nasty in there

[Tony Montana]

Hey thanks mimo. My main TV in the living room can do NTSC but i have only done it through scart. Will try it on that TV to see if i have any luck.

[mimo]

Hey thanks mimo. My main TV in the living room can do NTSC but i have only done it through scart. Will try it on that TV to see if i have any luck.

I have got the same thing, my TV (sony 32" CRT) will do NTSC, but only via SCART/S-Video etc. Not even a flicker on RF

[Tony Montana]

Hey thanks mimo. My main TV in the living room can do NTSC but i have only done it through scart. Will try it on that TV to see if i have any luck.

I have got the same thing, my TV (sony 32" CRT) will do NTSC, but only via SCART/S-Video etc. Not even a flicker on RF

 

Ahh OK, thanks for the info matey. Hopefully the CV is working then, just incombatability with the TV, Will try it thru my VCR's and see if i have any luck

 

Do you think a 1980's Betamax will do the job ?

[Tony Montana]

mimo - can i ask what video mod you did on your colecovision ?

 

Did you do Benheck's mod or something different ?

 

Thanks

 

Also, does anyone know about the wire coming from the pin on the expansion port ? Is this normal or does it look like it been added by someone ?

 

It's been a while since i had my other CV open, so i can't remember if it was there on that one

 

Thanks all

[mimo]

Unfortunately I dont have a Colecovision in my armoury as yet, but I would probably go for the 8bitdomain mod,(just because I'm not good enough to make my own) yes he is slower than a Canadian postie, but you will get the mod eventually http://www.8bitdomain.com/aboutcolecobios.php

I would also have to get one of these http://www.atarimax.com/usbcoleco/documentation/

[Tony Montana]

Unfortunately I dont have a Colecovision in my armoury as yet, but I would probably go for the 8bitdomain mod,(just because I'm not good enough to make my own) yes he is slower than a Canadian postie, but you will get the mod eventually http://www.8bitdomain.com/aboutcolecobios.php

I would also have to get one of these http://www.atarimax.com/usbcoleco/documentation/

 

Thanks again mimo. I think i'll try Benhecks mod first, to make sure the CV is actually working. If it does work, i'll invest in a 8bitdomain mod.

 

As far as the multi cart goes, i won't bother as i would prefer to buy original carts at the moment, thanks for the suggestion though

 

Thanks again for your help

[Ikrananka]

I am absolutley no expert in this but out of interest I have had a brief look over the "mod". And YES this is a modded NTSC CV, I have my one open here next to me and it has none of the wires and extra resistors etc that your board has.

 

In your first picture the wire connection down in the bottom right of the picture is connected to either the +5v or +12v power supply (after the power switch). I can't make out exactly where the wire connnects to after that - perhaps you could post some close ups of the connection points.

 

In your second picture the red wire is connected to Pin 39 of the expansion port. This pin is "EX_VDC_RST" - external video reset?? The schematics for the CV show this is connected to the "~Reset" pin of the CVs video chip (TMS9928A). The new resistor close to the red wire is within the Clock portion of the CVs circuitry. Again I cannot clearly make out where the other end of the red wire has been connected to.

 

The mod in the third picture seems to be messing around with the component (?) video (output from the CVs video chip (TMS9928A)) before it gets sent to the NTSC RF daughter board.

 

So it looks like some attempt at a video mod, but no idea what it was trying to achieve. Sorry I can't help more.

[Tony Montana]

I am absolutley no expert in this but out of interest I have had a brief look over the "mod". And YES this is a modded NTSC CV, I have my one open here next to me and it has none of the wires and extra resistors etc that your board has.

 

In your first picture the wire connection down in the bottom right of the picture is connected to either the +5v or +12v power supply (after the power switch). I can't make out exactly where the wire connnects to after that - perhaps you could post some close ups of the connection points.

 

In your second picture the red wire is connected to Pin 39 of the expansion port. This pin is "EX_VDC_RST" - external video reset?? The schematics for the CV show this is connected to the "~Reset" pin of the CVs video chip (TMS9928A). The new resistor close to the red wire is within the Clock portion of the CVs circuitry. Again I cannot clearly make out where the other end of the red wire has been connected to.

 

The mod in the third picture seems to be messing around with the component (?) video (output from the CVs video chip (TMS9928A)) before it gets sent to the NTSC RF daughter board.

 

So it looks like some attempt at a video mod, but no idea what it was trying to achieve. Sorry I can't help more.

 

Thanks for the info man ! I will take some closer shots of the "mod" and post them up. Thanks for the PM also

 

Much appreciated

[Tony Montana]

OK here are some closer shots

 

So the red wire comes from pin 39 on the expansion port and runs to here:

 

 

Then on the same point on the reverse side of the motherboard is this:

 

 

Which then runs to here:

 

 

Then there is this added bit underneath the RF modulator:

 

 

Hope that can help shed some light on WTF is going on here lol

 

Thanks for any further help

[MFoolsRun]

So I think I might have figured out what's wrong with my Colecovision.

 

I compared my motherboard to the photos of yours, and it looks like I'm short a capacitor. Upon closer examination, it looks like it may have broken off.

 

I don't know anything about electronics; I don't know if turning the system on and off with this capacitor missing could have fried it forever, or if simply soldering another one on could fix the fact that it doesn't produce a TV signal, but I thought I'd give it a shot anyway (unless someone here stops me).

 

But I need to know what kind of capacitor it is before attempting a fix.

 

Tony, can you tell me what it says on the capacitor I've indicated in the attached image?

 

Thanks!

Edited April 26, 2008 by MFoolsRun

[Tony Montana]

So I think I might have figured out what's wrong with my Colecovision.

 

I compared my motherboard to the photos of yours, and it looks like I'm short a capacitor. Upon closer examination, it looks like it may have broken off.

 

I don't know anything about electronics; I don't know if turning the system on and off with this capacitor missing could have fried it forever, or if simply soldering another one on could fix the fact that it doesn't produce a TV signal, but I thought I'd give it a shot anyway (unless someone here stops me).

 

But I need to know what kind of capacitor it is before attempting a fix.

 

Tony, can you tell me what it says on the capacitor I've indicated in the attached image?

 

Thanks!

 

Hey man, heres a pic of the cap in question. Sorry i can't help other than that. Don't know much about electronics myself.

 

I would try and replace the capacitor and try the Colecovision to see if it works. I doubt it would do it any harm anyway.

 

Are the legs of the cap still attached to the motherboard ? or does it look like it's been de-soldered ?

[MFoolsRun]

Are the legs of the cap still attached to the motherboard ? or does it look like it's been de-soldered ?

It looks like they're still attached.