Re: Vivitar 283 flash unreliable?

"PDM" <pdcm99[deletethisbit]@tiscali.co.uk> wrote:
"PDM" <pdcm99[deletethisbit]@tiscali.co.uk> wrote in message
news:4a969605_4@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

"Floyd L. Davidson" <floyd@xxxxxxxxxx> wrote in message
news:87bpm1h4xr.fld@xxxxxxxxxxxxx
"PDM" <pdcm99[deletethisbit]@tiscali.co.uk> wrote:
Remember it's the flash that provides the trigger voltage. The 283
produces
up to 18 volts (depending on model). And some old flash units produce
even
higher voltage. The effect of this is to ruin the camera's electronics.
Modern cameras require about 4 volts. Even old cameras don't like this
kind
of voltage. I've had a pentax spotmatic damaged by the 283.

The flash has a voltage on the trigger circuit when it
is *non*-active. That is not a "trigger voltage" in the
sense that such a term normally indictes (which would be
a voltage that triggers an event). The flash is
triggered by the flow of current when the circuit is
connected to ground through the camera (and that voltage
essentially drops to zero).

I simply do not believe a Pentax Spotmatic could be
damaged by the voltage. The technology used by the
Spotmatic is a metalic switch! It would have been
insulated for probably 300 or more volts, and a measly
18 volts from a 283 is not going to damage it. (That
low a voltage could mean more current though, and a
higher current could have damaged it. But not the
voltage.)

Well, it happened. Unless some other reason?
PDM
And also this from a thread:
http://photo.net/bboard/q-and-a-fetch-msg?msg_id=000Dwtas below:
Patrick Clow , Dec 09, 1999; 12:21 p.m.

Sync voltages can harm electronic camera circuits OR mechanical circuits! On
older mechanical shutters the shutter is the strobe switch for the PC. If
there is a lot of voltage present then a little bit of carbon will form
every time you fire the camera. Eventually there will be too much carbon
crud for the shutter to fire the PC (or it will happen internittently as the
shutter occassionally breaks off a piece of carbon from time to time). In
odd occurences I have heard of people's shutter contacts being vaporized by
a bizarrely high strobe voltage (I assume the camera's contacts were worn
beyond belief and the strobe was operating improperly -- makes for a good
scare story, though!).

Unfortunately, that is mostly untrue.

And second, "a lot of voltage present" does not describe
18 volts!

In fact the "lot of voltage" required to cause
enougharcing to deposit carbon is something well above
50 volts.

Note that I said the *voltage* is not what would have
caused the switch to fail, but I did not say that a flash
trigger circuit could not do it, or that even the 283's
circuit could not. It might, but from current rather than
voltage. In particular, a lower voltage might also indicate
a higher current. And that is a much more likely cause of
the slow deterioration of the mechanical switch contacts.

While switch contacts are easily insulated to well above
200 volts, they require precious metals such as silver
or even platinum be used for the actual contact region
in order to handle current without problems. And they
definitely have a finite life.

Hence the other point that needs to be emphasized is
that your Pentax Spotmatic probably required hundreds or
thousands of actuations to cause enough damage to the
switch for it to fail. Which is to say, it just plain
wore out! And that is to be expected.

But if you take a flash that has 300 volts across the
trigger circuit and try it with 100 each brand new
digital cameras rated to have no more than 10 volts on
the sync contacts, you will destroy 100 each brand new
cameras without actuating the shutters even a single
time. Just plug in a charged up flash unit, and kiss
the camera goodbye!

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@xxxxxxxxxx
.

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