Home-made power pack for a AF-540

[TimB]

Hello all,

I was pretty sure that this topic would have been covered by now, but I couldn't find much info on the great tubes of the internets.

As you may have guessed, the question is: can I jerry-rig something to serve as a ghetto power pack for a AF-540 FGZ?

I'm guessing that there is more than just a battery holder and a cord. Maybe an active chip that regulates max current, or something like that? Or is that circuitry in the flash unit itself?

Anyhow, I would be very interested in learning more about this if anyone has any info. If nothing else, for personal curiosity

Cheers,
Tim.

[RodConn]

It is actually a full flash power supply - by memory the output voltage is about 300V.

I assume this is to put in a higher current inverter than the one in the 540 to give a faster capacitor charge.

Rod

[TimB]

So, if I understand you correctly, the power pack goes directly to the flash lamp.
And the power pack itself regulates the supplied current/voltage.
Correct?

If that's the case, then making a DIY power pack is probably not the best idea

[RodConn]

Originally Posted by TimB

So, if I understand you correctly, the power pack goes directly to the flash lamp.
And the power pack itself regulates the supplied current/voltage.
Correct?

If that's the case, then making a DIY power pack is probably not the best idea

Correct

Rod

[felix68]

Originally Posted by TimB

So, if I understand you correctly, the power pack goes directly to the flash lamp.
And the power pack itself regulates the supplied current/voltage.
Correct?

If that's the case, then making a DIY power pack is probably not the best idea

I don't think that is quite correct. The power pack supplies approx. 330v directly to the capacitor in the flash, cutting out the voltage step up electronics. It is basically dumping the required power directly to the capacitor without having to convert the 4.8-6V that the AA batteries supply, up to 330V. The flash still controls how much of that power is uesd by the lamp.
A much easier route is to build a 6V SLA external battery pack that uses the contacts in the battery compartment. There are some instructions floating around using household fuses as dummy AA batteries to do this. I built a pack like this using some 1/2" dowel and a couple of brass screws. Works great with my Vivitar 285HV. I get recycle times of under 3 seconds on a full power pop using this much simpler pack.

[grhazelton]

Years ago I made a similar battery pack for a flash using the dowel and screw and a 4 D-cell holder. Worked just fine!

Speaking of the 540, does anyone know whether the external battery/inverter pack for the old AFT400 would be compatible? The AFT 400 used 6 AA's or the external pack, which used 6 C-cells.

Of course, it would be even nicer if Pentax had continued the excellent TTL system that the LX uses.... Could it be that there is a profit motive here?

[Ben_Edict]

Originally Posted by grhazelton

Of course, it would be even nicer if Pentax had continued the excellent TTL system that the LX uses.... Could it be that there is a profit motive here?

The old TTL system (I have a LX and several other film cameras, that support it) cannot be used by DSLRs anymore, because the sensors reflectivity is completely different from film. As TTL took the flash reading from light reflected by the film, the sensor would give a completely off reading and one varying with the chosen aperture, too.

Otherwise it is surely an economic decision to dump the additional flash sensor, which was still present in the istD and istDS, to allow the use of the old TTL flashes. But they worked poorly. In fact using just the auto-Thyristor control of any good flash unit provided much better results - at least that is my experience.

Ben

[JCSullivan]

Are GR Hazelton and Felix 68 still around the forum!!!!

I am thinking of doing something for an external power pack for the 283 and 285 - anyone have any ideas how to do this.