Of course, after the diode is put in and the battery box is modified,
the meter will still have to be recalibrated mechanically.
John
Frank van Lindert wrote:
>
> On Mon, 5 Apr 1999 13:03:37 -0500, Jay Maynard <jmaynard@xxxxxxxxx>
> wrote:
>
> >On Mon, Apr 05, 1999 at 12:09:47PM -0400, John Hermanson wrote:
> >> Modifying the OM-1 meter with the proper diode gives you a dead on
> >> reading at all light levels if used with the silver oxide battery. This
> >> mod essentially builds the MR9 into the camera.
> >
> >What *is* the proper diode? It would seem that a 1.35V Zener would be the
> >Right Thing, but they don't make those that I've found...
>
> As far as I know (from an earlier discussion) a certain Schottky diode
> will cause the needed 0.15 V voltage drop.
> I have even seen a description somewhere of a home made adapter which
> incorporates this Schottky diode. I have never seen the MR9, but it
> probably will be like this one, at least electronically.
>
> I will try to describe it in my best English....
> The base of the adapter is a round piece of printed circuit board with
> copper layers on both sides and with a diameter equal to that of the
> infamous mercury cells (so it will fit into the battery chamber of
> the OM-1)
> One hole needs to be drilled though the PC board, to take one of the
> wires of the Schottky diode. The hole must sit eccentric, as much as
> possible near the edge of the board. The Schottky diode must be placed
> on the top side of the PC board, with one wire through the drilled
> hole (mind polarity!). This wire must be soldered to the bottom of the
> board, and must not make contact with the top copper layer. The other
> wire of the Schottky diode must be soldered to the top. Cut the wire
> ends as short as possible.
> The Schottky diode must leave room for the silver oxide cell to sit
> next to it with its negative bottom contacting the topside of the PC
> board. The positive top will make contact to the cover of the battery
> chamber, as usual.
> Result of all this is a series connection of the silver battery and
> the Schottky diode. It is a pity I can't make a drawing of the thing
> (or even better: a photograph - but I have never contructed one
> myself. I probably will have to, now mercury cells are going to be
> banned in Europe too...
> If anyone feels himself challenged to make a few of these in series I
> will be happy to receive one and make that picture ;-)
>
> Best wishes from Holland
> Frank van Lindert.
>
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