Re: Monitor problem

["Michael J. Mahon" <mjmahon@aol.com>]

Giorgio Morocutti wrote:
> On Wed, 30 Jan 2008 15:09:53 -0800, "Michael J. Mahon"
> <mjmahon@aol.com> wrote:
>
>
> > Giorgio Morocutti wrote:
> >
> > > Goodmorning
> > >
> > > Some time ago you have spoken of monitor problems, and now I explain
> > > my problem.
> > > Monitor Apple A2M2010 (the flip monitor).
> > > During the work, all OK. 
> > > During the turn off, a very bright point appears at the centre of the
> > > screen for 6-7 seconds 
> > > With reference to 050-5020-A schematic ( right ?), can you help me in
> > > this repair ?
> >
> > So is the problem the bright point when you turn the monitor off?
> > Otherwise, it's OK?
>
>
> Yes Michael!
> My worry is the burn of phosphorus :-(
>
> A second monitor A2M2010 has not this problem.
>
> Thanks for the attention.

This is the result of the CRT not remaining biased off after
power is turned off.

I'd look for an open capacitor or resistor in the vicinity
of the grid and/or cathode bias circuits.  (I haven't found
the schematic yet.)

To make the spot invisible, it's necessary to hold the grid
sufficiently negative relative to the cathode for the 6-7
seconds that the HV persists and the cathode remains hot,
but the sweep is off.

-michael

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