I recently reported repairing a Vivitar 285 (below). I've now repaired
another one which would fire from the PC connection or from the test
button but not from the hot shoe contact. The problem was corrosion on
part of the PC contact designed to disable the hot shoe contact when the
PC cord is plugged in.
If you look into the PC cord socket you will see a silver contact. When
you insert the PC plug the tip of the plug makes electrical contact
there while at the same time pushing it in. When it's pushed in it
causes it to separate from another stationary contact that runs to the
hot shoe thus disabling the hot shoe when the PC cord is plugged in. I
found that the top and edge of the stationary contact was badly corroded
despite the fact that the flash was less than 3 years old and appeared
to be brass. A 20 year old version showed no such corrosion. It was
easily cleaned up with a small piece of emory board.
OT but many of you probably own Vivitar 283's or 285's which are no
longer available. These repairs were rather simple do-it-yourself.
Chuck Norcutt
Chuck Norcutt wrote:
> I was given a 285HV that was totally non-working in any of it's auto
> modes or manual fractional power modes. I was able to determine by
> substitution from another 285HV that the problem was with the sensor
> module.
>
> I fixed the 285 by disassembling and cleaning the sensor module.
> Internally it has metal wipers rotating along a circular track that
> switch tiny resistors in and out of the circuit when you rotate the
> sensor knob. The circular track had a thin layer of, presumably,
> conductive grease on it. The grease had congealed over the years and
> had turned into a non-conductive insulating film. I cleaned off the
> congealed grease with naptha and reassembled it.
>
> It now agrees to within 1/3 stop (and frequently less) in all modes with
> another 285 I have. It's still nowhere near the guide number of 120
> that it's supposed to be but neither is the other one. Both test at
> guide number 80-90 at ISO 100 and "normal" angle setting. Anyhow, I
> think it is now working as designed if not as advertised.
>
> I was quite surprised to see how it works internally. The photo
> sensitive diode is covered by a semi-circular rotating window that moves
> with the sensor dial. The window has 4 positions where the first is
> clear and the second through fourth are covered with increasing
> densities of tiny black dots which progressively reduce the amount of
> light striking the sensor. Kind of an el-cheapo ND filter.
>
> Maybe this treatment will rejuvenate one of your old flash units. The
> sensor is composed of 3 pieces held together by 3 screws. To
> disassemble the sensor for cleaning remove the two philips screws from
> the back side of the sensor. Remove the back 1/3 which is soldered to a
> couple of wires. No need to unsolder. Remove the "axle" screw that is
> now revealed in the center of the remaining front 2/3's and separate the
> other two pieces. They are quite stubborn in resisting separation but
> continue pulling and wiggling until they come apart.
>
> Clean the circular tracks that will be revealed at center and perimeter
> of the center piece. Caution: There is a small semi-circular window in
> on piece and a (perhaps 6mm diameter) window on the back side of front
> piece of the sensor. These can easily fall out. The semi-circular
> window has a right and wrong orientation which is controlled by a notch
> at one corner. Bend the wipers up a bit to assure a good spring contact
> and then reassemble.
>
> Chuck Norcutt
>
>
>
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