Introduction:
My Metz 58AF-1 got defective zooming mechanism than I bought a Metz
58AF-2 after 3 years the flash tube blew into peaces, I opened it to try
to replace the tube and found out that the tube is too small and can be
overloaded too easy. I reworked the head to fit a bigger tube, but the
flash did not trigger anymore......
I mostly used the Metz in the automatic mode using the light sensor of
the flashgun, if you know what you are doing, this is very reliable and
accurate and no problems with the bride closing her eyes on the pre-flash!
I decided to use one of my old Philips flashguns, the Philips P36-TLS.
This flash was build by Nissin more than 40 years ago.
* Very reliable, plenty of them on the secondhand market (in Europe)
* The flash-head is fully swivel-able and tilt-able.
* It has a sub-flash
* It has a manual mode with three levels and
* an automatic mode with three aperture-ISO combinations.
In automatic mode, it uses its own sensor and the accuracy was more
than good for slide film, so certainly good enough for the K1 sensor.
Unfortunately the hotshoe only has one contact: the trigger contact.
I found out that I could modify the flash and can add a "flash ready"
contact.
The "ready" contact for Pentax is the contact, looking from the back of
the camera, that is the nearest at the right side.
I measured another flashgun with "ready" contact: the "ready" voltage
generated by that flash is about 2.7V.
After firing, the voltage drops to zero and comes back when the gun is
ready for the next flash.
The K1 (and probably all DSLR) uses the signal to
* to light the flash ready sign in the viewfinder
* to limit the shutter-time to the max flash sync time
* to add "flash did fire" in the metadata of the picture (this is the
most important to me)
Measuring the trigger contact of the flash showed 3.9V. To ignite the
flash, the K1 pulls it down to zero and after the flash, the voltage
goes back to 3.9V when the gun is ready for the next flash.
I concluded that probably the ready signal could be derived from the
trigger voltage by connecting them through a resistor.
After some experimenting I settled for a resistor of 22k Ohm.
This works perfectly!
With the 22k connection, the trigger voltage drops to 3.4V and the ready
voltage is 2.3V
I did some tests to see how critical the value is:
33k still okay,
68k --> ready signal too low
10k --> still okay but triggervoltage drops to 3.2V (but triggering
still fine)
22k is a good compromise for this flash-camera combination.
Now I took the DREMEL and cut off the hotshoe that only had the trigger
contact and glued an old hotshoe with trigger and ready contact and the
22k resistor.
Greetz, Jos van der Hijden.
--
Greetz, Jos
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