I had two very old QA310's I bought "as is" a long time back with various
maladies.
I wanted some flashes to modify for a project, so stripped one down and changed
it, so it could
use NiMh cells. I am going to remount the flashtube later to turn it into a
bare bulb unit.
The original inverter transistors are small germanium ones and are limited to
about 1Apk so using
NiCd's or NimH cells kills them. I replaced them with very beefy PNP power
transistors: NTE154
(equiv Tip32) transistors and these seem to work really well with NiMh cells,
as well as improving
cycle time. I cut of the transistor tabs so they fitted better and insulated
the metal face with
some mylar tape. The leads needed to be dressed differently, to drop into
original transistor
holes. Peak currents now go to over 3A. The two inverter transistors are easy
to identify, as they
have little heatclips on them. I must have set off a few hundred full dump
flashes while testing
and although the plastic reflector got pretty hot, the transistors hardly
seemed warm. Using new
Alkalines still gives a little higher flash output, provided you wait long
enough, but the NiMh
are more consistent and faster. A T32 with NiMh, still cycles a little faster,
even with this mod
to the QA310.
Taking the QA310's apart is a real pain as there is a small spring etc to lose.
There is an
obvious screw in the battery compartment and less obvious screws under the
metal trim on back
panel, after removing the central srew on the dial assembly using friction. The
case has some
plastic clips at front sides and back, this requires careful prising to open.
The normal trigger voltage is fairly high : 220V measured/loaded by a 10MOhm
DVM. I am going to
add a low voltage trigger cct.
Take care to avoid the lethal high voltage energy stored in the flash cap, if
you open your flash
to do this mod! Charge is stored for a long time after switch off on a couple
of large caps.
Tim Hughes
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