Question on ColecoVision Power Supply Repair

[Coolhand20th]

My Power Supply suddenly stopped working, and after cutting open the supply, I tested all the regulators and came up with a 1.3 on the +5. So after going to Radio Shack and purchasing a 276-1770 (7805) replacing the regulator was very easy. However after installing it now I am getting almost 8 volts out of it which seems very high to me. The rest of the regulators test out perfect at 12.3 and -5.1. I never had a problem till recently with this power supply.

 

Was wondering does that voltage seem high to anyone else? Should I be concerned or is it normal on some of these to be that high?

 

Or could I have a bad part out of the box?

Edited February 25, 2012 by Coolhand20th

[cOLeCoHiTMan]

You're only the second person I've heard of trying this... here's the video from the first

[Coolhand20th]

Yep that is the video I watched before I tried this. I'm having a hell of a time finding a Power Supply so figured I would try this but that 8V just seems to high for me. Idk what to do.

[cOLeCoHiTMan]

http://4jays.net/store//page84.html

$17.95

[Coolhand20th]

http://4jays.net/store//page84.html

$17.95

 

Thanks, may just have to break down and buy one. Don't want to but not much I can do right now. Still very unsure of that 8v, hopefully someone else around here has done that fix before.

[cOLeCoHiTMan]

Just relisted on Ebay 10 available:

eBay Auction -- Item Number: 220963078307

[Coolhand20th]

Just relisted on Ebay 10 available:

eBay Auction -- Item Number: 220963078307

 

Sweet! Thanks alot Brett!

[Coolhand20th]

Make that 9 Available!

[atariluvr77]

My Power Supply suddenly stopped working, and after cutting open the supply, I tested all the regulators and came up with a 1.3 on the +5. So after going to Radio Shack and purchasing a 276-1770 (7805) replacing the regulator was very easy. However after installing it now I am getting almost 8 volts out of it which seems very high to me. The rest of the regulators test out perfect at 12.3 and -5.1. I never had a problem till recently with this power supply.

 

Was wondering does that voltage seem high to anyone else? Should I be concerned or is it normal on some of these to be that high?

 

Or could I have a bad part out of the box?

 

I'm getting 8V too, so it's not a bad 7805... I think the 5V rating on the 7805 is under a load, with 8V being the no load output... I'm sorta afraid to try and power up a console with it putting out an extra 3v, but I may try it...

 

I think a 3V regulator might be whats needed here, because it would put out about 5V without load like the oem power pack... the shack doesn't carry anything with those specs.

[atariluvr77]

What I find even stranger, is that I have 2 power packs that are putting out the correct voltages +12, -5, +5 -- and they STILL will not power up a machine correctly... one pack causes black screen with hum, the other pack shows a picture that is constantly rolling (happens with multiple consoles)... if I use a known good power pack on the same consoles everythings fine... explain that one to me.

[+boxpressed]

What I find even stranger, is that I have 2 power packs that are putting out the correct voltages +12, -5, +5 -- and they STILL will not power up a machine correctly... one pack causes black screen with hum, the other pack shows a picture that is constantly rolling (happens with multiple consoles)... if I use a known good power pack on the same consoles everythings fine... explain that one to me.

 

Are those the "bad" PS I sent you, atariluvr77? I thought you could get one to work.

[+boxpressed]

You're only the second person I've heard of trying this... here's the video from the first

http://www.youtube.com/watch?v=TfO1VFQBAvY

 

Man, music videos have gotten a lot worse these days.

[atariluvr77]

LOL... yeah that video doesn't really help much because his description said the +12 and +5 regulators were available at ratshack but doesn't give part numbers... I think he was referring to the 7805 for =5 but it is not a correct match...

 

What I find even stranger, is that I have 2 power packs that are putting out the correct voltages +12, -5, +5 -- and they STILL will not power up a machine correctly... one pack causes black screen with hum, the other pack shows a picture that is constantly rolling (happens with multiple consoles)... if I use a known good power pack on the same consoles everythings fine... explain that one to me.

 

Are those the "bad" PS I sent you, atariluvr77? I thought you could get one to work.

 

I think they might be, can't be sure though because of all the parts I have lying around in no particular order. One of yours definately worked, atleast initially. The one I opened and installed the 7805 is NOT one of the ones I got from you because I measured the voltages on yours when I got em and they checked ok... The one I'm talking about above was only getting +2v so I tried the replacement regulator. It was worth the gamble...

[Cubesmith]

I'm getting 8V too, so it's not a bad 7805... I think the 5V rating on the 7805 is under a load, with 8V being the no load output... I'm sorta afraid to try and power up a console with it putting out an extra 3v, but I may try it...

 

I think a 3V regulator might be whats needed here, because it would put out about 5V without load like the oem power pack... the shack doesn't carry anything with those specs.

 

I realize this is an old thread but I'm experiencing the exact same problem. Did you ever try the power supply at +8vdc with the 7805 installed?

 

I have a Canadian supply on the way, but would still like to sort this one out too.

 

Thanks

Chris

[atariluvr77]

Yes, I did go ahead and try it briefly... it powered the system just fine but there were diagonal lines moving across the screen in front of the Colecovision display... I assume because there was too much juice on the 5V line. I unplugged it and havn't tried it again because I didn't want to fry my Colecovision. I really think a 3V regulator may put out 5V since the 7805 regulator is putting out 8... I was going to try to put a resistor in there to bring down the voltage too but havn't gotten back to it...

 

Long story short, it works if you don't mind the interference but I don't know what the long term affects would be on the machine.

[Cubesmith]

That's too bad. Guess I'll be using the arcade psu until my Canadian model shows up.

 

Thanks for letting me know.

[Osgeld]

I'm getting 8V too, so it's not a bad 7805... I think the 5V rating on the 7805 is under a load, with 8V being the no load output... I'm sorta afraid to try and power up a console with it putting out an extra 3v, but I may try it...

 

I think a 3V regulator might be whats needed here, because it would put out about 5V without load like the oem power pack... the shack doesn't carry anything with those specs.

 

the 78xx series does not need a load to regulate, that's the whole point of a regulator, you can drop one on a breadboard and measure 4.99 +- tolerance volts with nothing hooked up to the output, the only times I have seen this happen is when AC is getting to it, or its oscilating ... meaning the caps around it are crap

 

either would cause noise on the 5 volt line which may interfere with sensitive functions such as video, your lucky it did not fry anything as most digital IC's are not rated for more than 7, and usually are only rated for 10% over max (ie 0.5 volts)

 

regulators typically don't up and die, something else causes them to die, fixing the symptom does not fix the problem

Edited April 23, 2013 by Osgeld