DF500 Version-Specific Hookup Information

Version 1.0, February 27, 2004


Several PowerSlaves have died during installation by others as well as myself.  I believe I have pinned down the cause to the following scenario:

Touching both the PowerSlave board and the Vivitar flash board at the same time after the flash capacitor has been charged (possibly during testing, before beginning the modification or after the modification has been done) will often destroy the sensitive CMOS circuitry in the PowerSlave.  This happens even (especially) if the batteries are disconnected.

This occurs because easily touchable parts of the Vivitar board are at -265 volts (or more) compared to all the circuitry on the PowerSlave;  skin resistance is easily low enough to destroy the CMOS circuitry if components or circuit traces of both boards are touched simultaneously.

To avoid this eventuality, I can only suggest one thing:  one must ensure that the flash capacitor (and even the smaller yellow commutating capacitor) are discharged before handling the boards, and if possible, avoid even testing the assembly until everything is safely installed in the intended housing.  If the flash is brand new out of the box (or the unmodified flash unit has not had batteries in it for a few weeks) it is safe to assume that the capacitor is not charged enough to cause a problem.  If the Vivitar flash has been powered up for testing (especially if the resistors have been cut per the modifications below to prevent draining the flash capacitor), the flash capacitor will need to be discharged before wiring the PowerSlave to it.  If the assembly (PowerSlave wired to Vivitar board) is tested after wiring but before installation in its final housing or box, the aforementioned capacitors should be discharged before handling the assembly for mounting.

A suitable device for discharging the capacitor can be made from a metal-oxide-film (MOF) resistor in the 100-ohm to 1000-ohm range, rated at several watts.  Wires with insulated alligator clip leads can be added to the resistor so it can be easily clipped to the leads of the capacitor to discharge it.  Only a few seconds should be required for the capacitor to be significantly discharged.

On the DF500 version of the Vivitar board, two resistors need to have one lead clipped (or lifted from the board) in order to disable the automatic flash adjustment circuitry and the "Ready" indicator:  The 10K (brown-black-orange-gold) indicated and the 1M resistor (either brown-black-green-gold or brown-black-black-yellow-brown) near the neon "Ready" indicator.

The wires from the PowerSlave board are attached as shown:

In the photo above, the Battery Ground (black) and the Switched Output (blue) are shown connected across the switch -- for operation in this mode, the switch is left in the OFF position during normal operation, and the PowerSlave is on whenever batteries are installed.  When the switch is turned ON, the power-saving mechanism of the PowerSlave is defeated, and the flash's capacitor will be charged to the full voltage possible with the given battery voltage.  In the photo above, the switch OFF position is to the left, and ON is to the right.

NOTE: Wire positions are not optional at the switch nor at the flash contacts -- the wires must be connected to the PC traces as indicated.  The PowerSlave may be damaged if the black, blue, or white wires are not connected as shown.

If the "guts" are to be remounted into some other project box, etc., it may be advantageous to eliminate the smaller DF501 board. This may be done by removing the yellow capacitor from the board and soldering the green and yellow wires directly to it.  Then the remaining three wires that went between the DF500 and the DF501 boards may be de-soldered or clipped off at the DF500 board.  Picture later.

2004 Jon Barclay, all rights reserved.