Sunday, February 10, 2008

Vivitar 283 Hacking

For some reason or another, the Vivitar 283 which I purchased on e-bay stopped working yet again. I thought it was more of the battery corrosion or something, but apparently that wasn't the case.

I first tried modding the battery compartment to run a couple wires in there. But it failed to work. I was getting pretty annoyed at having wasted $30 and the freight forwarding fee; I didn't know why the inverter wasn't working (couldn't hear the inverter whine).

Read through Sam Goldwasser's Strobe FAQ which mentioned that the obvious failure modes in flash inverters are the transformer and the chopper transistor. Now it's been a long long time since EE 25 and I don't think it's possible anyway to test a transistor in-circuit.

Anyway I was cursing my luck and had the strobe in pieces in front of me.



I neglected to note that I had left it on and it was connected to the 6V gel cell.. the outcome is obvious. My finger grazed the huge flash capacitor and I got this sensation like someone had driven a red-hot needle through my finger. Immediately realizing what was going on, I tested the voltage across the flash capacitor with my trusty 165-peso digital multimeter and guess what... 160-odd volts.

Not enough to light the "ready" indicator but enough to give me a small shock. I figured that the inverter was working, but not well enough (nominal flash capacitor voltage is 300-plus volts). So I un-soldered the original wires for the power, and soldered lamp cord directly to the switch and the collector of the chopper transistor:



I used color-coded lamp cord to avoid strobe-destroying accidents. At this point, after powering it up, I could hear the distinctive inverter whine, and the flash would fire when I pressed the test button.

When I put the 283 together, I didn't put the battery compartment in anymore (since with all my screwing around the inside of the strobe, it will never take AA batteries again).



This is OK because I don't intend to use AA batteries (I gave away my AA NiMH batteries to my brother, and I don't want to buy new ones, they're expensive at $5 each).

Here I'm testing the trigger voltage. It's around 110 volts according to my 165-peso multimeter. Well within the capabilities of the EOS 350D (which has a 250V sync voltage). That is, if I trust my $500-plus DSLR to my $4 Chinese-made multimeter.



Final result: it's got that wire dangling out which somewhat interferes with the EOS control dial, but I've got a Quantum power pack on the cheap! I don't have a charger for the 6V gel cell, but a Nokia phone charger should do (it puts out about 7V).



I'd like to think I'm "l33t" for both restoring the Vivitar 283 to good condition; and for wiring up a Quantum-alike battery pack. But the reality is I'm too poor to buy a Speedlite 420EX or something. But the Vivitar 283 will do fine.

1 comment:

Photoful said...

250v sync on a 350D?

canon cameras only support 6v on the hot shoe.

you will fry yours