Re: Apple II monitor (green screen) doesn't turn on or show light on switch

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

aiiadict@gmail.com wrote:
> IIe monitor started smoking today...
>
> It gave into social pressures and lit up.
>
> :-)
>
> I opened it up.  diode in the ?bridge rectifier? is split in half,
> burnt.... 4 diodes in a row
> right next to AC input on the circuit board.
>
> Is this just the diode failing, or something in the DC circuit drawing
> too much
> power?

Yes, it's almost certainly a full-wave bridge.

Were you using the monitor (looking at the screen) when
it failed?  What did it look like?

Are there any other parts in the monitor which appear
to have overheated?

How's the quality of power in your area--do you have lots
of lightning and no (or blown) surge supressor?

One sure-fire way to fry a diode is for something downstream
to have shorted B+ to ground--like a filter capacitor.  A
bypass cap (typically 0.1uF) could also short and cause this,
but in my experience, they often "pop" and remove themselves
from the circuit.  ;-)

Without knowing more about how it failed, I think your chances
of repair are good.  The only possible show stopper would be
a special component failure, but I'd put that under 30%.

With more info, we can guess better.  ;-)

(BTW, do you have a schematic for this monitor?)

-michael

Music synthesis for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."