On Mon, 3 Jan 2011 14:00:38 -0000, "John"
wrote:

It was working and I was getting used to it and then it failed. Tried fresh
batteries and it is erratic. I hear it whining as it charges but the ready
light isn't coming on. If I press the manual button I can see a faint
flicker in the flash tube and the green light flickers.

Has anyone got any ideas about how these fail?

Possibly just slightly corroded battery contacts - so try cleaning
those first. More usually though it is the large high voltage
electrolytic capacitor which acts as the tubes energy store develops a
leak (partial short circuit). If unused for years it needs
"reforming" before being put back into use.

Replacing them isn't too difficult if you can solder but beware - even
a leaky capacitor of that voltage (about 300VDC) and size (about
800uF) can administer a very large shock so ensure everything is
discharged before playing with it.

Finding a replacement of the right dimensions and characteristics may
not be simple. Normal electrolytic capacitors don't survive the
rather brutal regime of a flash gun too well and a photoflash rated
capacitor may be difficult to find. That said if you don't use it too
much a standard capacitor will work - it just won't have a very long
life.

There are some Vivitar 2000 series photos at
http://www.pixcontroller.com/forums/...?showtopic=336
which will give you some idea of the layout.

By the way - be careful using old flashguns on modern cameras. Many
cameras flash trigger circuits on the top hotshoe are only safe at low
voltage (5V or so) and some old flashguns can have several hundred
volts on the trigger connector.

The Vivitar 2500 has about 12V on the shoe so is a bit iffy.

http://www.botzilla.com/photo/strobeVolts.html