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Remove preflash from A70 with Charles Naumann unit?

Henning Jensen
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I had been trying to build a small unit to "remove" the preflash from
my Canon A70 flash, so I can use my "Braun 370 BVC", as main flash. I
use standard Rowi "Synchro photo slave 301".

I have found good starting point in Charles Naumanns web page on:

I have build this unit, but seems not to work. I have found that the
370BVC-flash has 21 Volt between the hot-shoe contact, where it was
expected to be around 9 V.

I have therefore change the R1 to 1000kohm and R2 to 20kohm, to lower
the currents, but still not working well. It seem that it need several
"preflash" before the main flash goes off. The time constants may have

Anyone who could redesign this unit for the new conditions, so the
time constants and so on still are equal ? Maybe my mail to me
directly? But I think it could be widely used this unit - many old
secondhand flashes around?

Best regards

Henning Jensen
from Denmark

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