Color display won't power on!

Hardware questions and modifications

Color display won't power on!

Postby Eric » Wed Jun 24, 2015 9:30 pm

Crap, I was making arrangements with Hargle for a new system unit and I went to test my monitor today (Well, I was actually just going to mess around in Cartridge BASIC) for the first time in a few months and the damn thing won't come on.

No power LED, nothing. So I popped her open and checked the fuse. It was good. Then I checked the switch. It's good too. Then I checked the AC cord for breaks… continuity was perfect.

Then I decided to look around and all the connections seem right, but I reseated some to be sure and I also didn't see any bulging or leaky capacitors.



Seems like I'm having bad luck getting into this hobby. What else is there to check? I'm sure that it can be brought back to life and I'd rather do that then replace it or resort to another display.

It says nothing in H Kennedy's MONITOR.DOC, I'm not a repair guy and I'm all out of ideas.

Help will be appreciated.
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Re: Color display won't power on!

Postby Eric » Wed Jun 24, 2015 9:41 pm

For convenience and clarity, I'll list what I've found here:


-Fuse is GOOD
-Switch WORKS
-Cord has no breaks.

-Does NOTHING when switch is closed.
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Re: Color display won't power on!

Postby Eric » Sun Jun 28, 2015 11:42 am

So, I checked the headers for the power switch and jumped them and there is indeed power flowing through it, but the LED and CRT do absolutely nothing.

I didn't bang it around and have no idea why it would suddenly stop working while it was powered down and unmoved. These don't seem like the symptoms of dried-up caps and seem more like a broken connection somewhere, but I'm not sure. I have nearly zero experience working in CRT displays and don't really wanna poke around too much. It would suck to knock something loose and make things worse and it would be pretty inconvenient to kill myself.
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Re: Color display won't power on!

Postby jmetal88 » Sun Jun 28, 2015 12:00 pm

Maybe there's an open diode in the power circuit or something? Are there any resistors that look burned up? I'll look for a schematic later and see if I can't come up with any better ideas.
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Re: Color display won't power on!

Postby Eric » Sun Jun 28, 2015 4:07 pm

jmetal88 wrote:Maybe there's an open diode in the power circuit or something? Are there any resistors that look burned up? I'll look for a schematic later and see if I can't come up with any better ideas.

I didn't notice any fried resistors or diodes, but that is an idea and it is worth checking out again. I'll share what I find, or just let it be known if I don't find anything.
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Re: Color display won't power on!

Postby Eric » Sun Jun 28, 2015 4:37 pm

Well, seems like every diode I was able to test works.
However, I did snap a few pics while I was in there, though some of them are probably pretty useless.
And if Imgur compressed these like I'm guessing, there's probably not much to see.


http://i.imgur.com/XW67Q9T.jpg


http://i.imgur.com/vxeuxab.jpg



http://i.imgur.com/WVI7gIl.jpg


http://i.imgur.com/pfbiti4.jpg


http://i.imgur.com/7kVVzWn.jpg


EDIT: Eeyup, they got pretty compressed and made it all look more dusty than it actually is. But to be fair, it is quite dusty in there.
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Re: Color display won't power on!

Postby jmetal88 » Sun Jun 28, 2015 5:45 pm

You know, I wonder if there's a relay in there that's just not making contact anymore? That happened with my current TV a couple of times. I haven't checked the PCjr monitor for anything like that.
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Re: Color display won't power on!

Postby Eric » Mon Jun 29, 2015 7:51 am

jmetal88 wrote:You know, I wonder if there's a relay in there that's just not making contact anymore? That happened with my current TV a couple of times. I haven't checked the PCjr monitor for anything like that.

I think I may have seen a relay in there. I'll have to check. I crashed right after uploading those pics.
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Re: Color display won't power on!

Postby Eric » Mon Jun 29, 2015 1:39 pm

I checked every diode I can find, they all seem to be fine. I've also reconnected all of the connectors in case something worked its way out over the last thirty years and nothing.
No LED, no hum or buzz, nothing I can tell.
The thing just doesn't wanna turn on for some reason.


Would it be a good idea to start a thread somewhere, like The Vintage-Computer Forums or something?
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Re: Color display won't power on!

Postby jmetal88 » Mon Jun 29, 2015 6:30 pm

Man, I wish I could look at it in person... I bet I could diagnose the problem if I could. I doubt we live close enough, though. Never ran into anyone else on any of these forums from the Kansas/Oklahoma area.
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