Re: Monitor problem

[Giorgio Morocutti <giorgio.morocutti@alice.it>]

On Fri, 29 Feb 2008 01:31:54 -0800, "Michael J. Mahon"
<mjmahon@aol.com> wrote:


>I went back to the schematic, and I have one more possibility, based
>on the theory that the monitor *always* unblanked during powerdown,
>but the power supply voltage held up long enough to keep the scan
>going until the HV started to drop, causing a bright, shrinking
>*raster* at powerdown instead of an instant collapse to a dot.
>
>The likely electrolytics (!) are both in the +15v power supply:
>Cx01 and Cx03 (x=6?--hard to read...), which are 3300uF @ 35(?)v
>and 47uF @ 25v.  Of the two, the 3300uF is much more likely to
>be the culprit.
>
>Because of the way the power supply is designed, a short "holdup"
>time could also be caused by low input voltage to the 15v regulator.
>The most likely causes of this are 1) one or two diodes (or their
>leads) open in the bridge rectifier (D401,2,3,4) or, 2) excessive
>load current on the 15v line (which could be almost anywhere, but
>should cause something to be running too hot).
>
>Some voltage measurements at the input and output of the 15v regulator
>would cast light on these possibilities.

Thanks Michael for your help !

In the meantime, for my consolation, I have installed the
PC-transporter card on IIe with IBM keyboard, IBM CGA color monitor,
AE drive 3,5"and  with Olivetti DOS 5.00  and all works fine !
(I have found same cable at an electronic  fair ! ;-)  ) 

Same photos at http://fotoalbum.alice.it/giorgio.morocutti/
Work is in progress !!!

Thanks, ciao

Giorgio

Giorgio Morocutti
giorgio.morocutti@alice.it
Apple II & Apple III forever !