If you have some skills and tools why not do it yourself. Just follow exactly the procedures so it will take you out from the harm of the high voltage generated by the flashgun. Once you completely disassemble this unit you will only need to clean the all the contacts to make it work again.

1. Open
the battery compartment of the flash and remove the battery holder. The
flash uses four "AA" batteries that slide into a holder that is then
inserted into the flash. Use an eraser on the end of pencil to clean
all the contacts, both in the flash, the holder, the battery
compartment door and the batteries themselves.
2. Replace
the batteries in the correct order in the holder, insert the holder
into the flash, close the compartment door and turn the flash on by
sliding the power switch on the back of the flash. When the flash is
fully charged you should see a small orange blinking light next on/off
switch.
3. Rotate
the front power dial to "M" for manual mode. Press the blinking light
to discharge the flash.This will fire the flash at full power.Do not
look into the flash when you test it.
4. Rotate
the dial and test each of the four different color settings of yellow,
red, blue and purple. Each of these settings changes the power output
of the flash.The change is significant enough that you should be able
to see and hear the difference.If you have a hand-held light meter you
can test each setting. This will tell you if the circuitry is
performing correctly.
5. Clean
the hotshoe connection on the bottom of the flash using the eraser on a
pencil. Attach the camera to a manual film camera, set the shutter
speed to 1/60th of second, which is the most common sync speed of film
cameras and see if the flash fires.

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