On Wed, 12 Jun 2002 10:21:11 +0100, "Andrew Tierney"
<urbex@xxxxxxxxxxxx> wrote:
>In Manual GN16, not on a body, the autocheck light blinks after the flash
>regardless of if the "O" in "Olympus" is covered. This is wrong - if it was
>meant to flash (which I don't believe it is), then it shouldn't with the "O"
>covered.
No, this is quite normal. The flashing light shows that the flash tube
has been quenched rather than dumping all the capacitor charge - this
is what happens at GN16 so your flash is OK in this mode.
>In all normal auto modes, the autocheck light blinks unless I put my finger
>over
>the "O", suggesting all three of these are working normally.
>
>So, it seems to be some kind of problem with the switch (possibly?).
Don't think so.
>I had these ideas for fixing it:
>
>I assume that the TTL socket on the side of the T32 (small 5 pin connector)
>derives flash quench from the OM 2n if it is working properly. If it isn't,
>then
>the quench is simply when the flash shuts off. If I use an oscilloscope to
>monitor the "flash sync" and "flash quench" signals, when on and off of the
>body, in manual, and auto modes, I should be able to see timing differences. If
>not, then the flash is at fault.
>
>I also assume the Hot Shoe 4 is just connected straight through, so I will do a
>continuity test on it.
>
>I don't know what exactly signals things on the hot shoe, either a circuit
>closing or a voltage, but I could monitor this on the OM 2n to see if that is a
>problem.
The flash trigger (centre contact) is basically a switch to ground.
The quench signal (LH pin) appears to be a voltage fed form an output
of an IC, but I don't know the pulse length or its polarity. It
operates when the comparator switches over when the integrated light
over time says "enough". It's the same basic method that closes the
shutter. It's a beautifully simple, all analog circuit.
Regards
John Gruffydd (Mold, Wales, UK)
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