Re: Help diagnosing problem.

From: Patnukem <patnukem_at_email.domain.hidden>
Date: Sat, 3 May 2008 20:19:25 -0500

I adjusted the back knobs and the contrast one inside with no picture, I did not see any filament light up. I know a bit more about crt's then lisa's so this should be easer then the other problems. My last big project was repairing a 1951 tv I found in a barn and someone that helped me with it taught me a trick with a neon tube, by holding it next to the flyback transformer you can see it light up without touching anything (If they flyback is getting juice) then you can tell if the power is getting to it. I can also test the inputs to the video board for the +33v and the +12v (from the schematics) that should be there but I will wait until tomorrow when the crt has has a bit of time to dissipate.


On May 3, 2008, at 8:05 PM, James MacPhail wrote:

>>> the power button shuts the computer off
>>> so the cpu board must be working now, it also now attempts to
>>> read a
>>> disk when it is inserted and then ejects it (I guess it must do that
>>> when it can not read it) and the 3 beeps (two high one low) are
>>> followed by three more but are all the same tone.
> This means that:
> - the self test passed
> - your memory is good (probably), so you should see an image
> - you need a keyboard and mouse
> So, you need to address the no-video issue.
> Did you try the white contrast/brightness knobs sticking out of the
> back of
> the Power Supply? If misadjusted, the screen will be black.
> Can you see the CRT filament light up?
> I suppose some voltage measurements on the video board come next....
> James
> >

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