Re: How picky are power transitors ?
From: James Sweet (jamessweet_at_hotmail.com)
Date: 12/05/04
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Date: Sun, 05 Dec 2004 19:46:11 GMT
>
> The monitor in question is totally 100% dead. No HV, no LED, not even
> degauss.
>
Is there a ticking or chirping noise?
> I have measured (very carefully) voltages on the board. I seem to have a
> good B+ line but absolutely NO lower voltages. 12V and 18V points are
> marked but are still dead. I feel the problem most likely lies in the
> power supply. (However when the monitor died it did loose H-sync for a
> second then the mains filter cap exploded, could this mean the HOT is
> also dead?)
>
It's entirely possible that the 12v and 18v supplies come from the flyback
transformer which is part of the horizontal circuit so if that's not working
those voltages will be dead. If the HOT is bad I would expect you have a
blown fuse or flameproof resistor that supplies B+ to it.
> Does THIS transistor have an inductor parellel to it normally? As far as
> I can see the HOT is OK (not blown up, etc).
>
I have no idea, I don't even know what monitor we're talking about here.
> Thanks for the link to the NTE cross reference software (downloading on
> dial-up is painful).
>
Don't download the software, the cross reference is available on their
website so you can just use it there.
> Are you aware of any other good resources I should know about? For
> instance a circuit diagram for this particular monitor would be VERY
> helpful, do I have to pay the manufacturer for that (compaq)? Or are
> they available elsewhere?
>
Compaq (and many other monitors) aren't made by the company who's name is on
them, they just pay whatever other manufacture gives them the best price to
build a bunch of monitors with their name on them. Schematic diagrams are
rarely available even from the manufacture as monitors are usually
considered to be disposable by them. Once you fix a few monitors it starts
to become fairly easy to do it without a schematic though.
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