Most of us who have been using flash with our dSLR cameras are aware that vintage flash may have high trigger voltages capable of damaging the electronics of our cameras. Best practice is to always test and if there is any doubt use a safe-sync or similar adapter between the camera and flash. I totally get it and am religious about never using my vintage Vivitars (both over 200V) on anything other than on cameras of similar vintage or older.
The previous paragraph is just so y'all know that I know that those flash are dangerous. To complete the picture, I also know that it is the current through the sync circuit when the flash fires that does the actual damage. The rest of this short essay is to show that knowing and even applying reasonable caution are sometimes not enough.
Many of us know that Pentax sells accessory 5P adapters and cables to allow wired off-camera use of digital protocol flashes. I have a small set of these consisting of
- Hot-Shoe Adapter F - five pole foot with both 5P connector and hot shoe on top
- Off-camera Adapter F - cold foot with both 5P connector and hot shoe on top
- Sync Cord F 5P - Short version of 5P cable
One can do a lot of fun stuff with those three components, including testing of contact state for various types of flash and flash modes. It was in this last context that I did my stupid thing. It started with doing familiarization with a recently acquired Vivitar 283 (original MIJ version) having a measured trigger voltage of 260V.
Having set the 283 aside, I spent some time this morning helping a PF user who had a 5P setup question and also confirming my previous understanding of the three components above. Part of that was confirming that both the hot shoe on top and and the the 5P connection were simple pass-through from the adapter foot and that the circuits were not isolated from each other. This was easily done by putting all three of the parts above together and doing continuity testing between the contacts on both hot shoes and the pins on the Hot-Shoe Adapter F foot. Sure enough there was continuity of like with like between all three interfaces.
That last is a good thing to know and something that translates to implications for use of various devices (e.g. O-GPS) in combination with things like flash. I must have been bored since I continued fooling around with the setup. Even though I figured the hot shoe adapter was just a simple junction device, I decided to check to see if it included voltage reduction. Enter the 260V Vivitar 283 on the top shoe. On the off-camera adapter was my YN560 III speedlight, still turned on as from testing center contact voltages. I had no concerns since the Vivitar was turned off, so slipped it into the shoe, flipped the on switch and measured the adapter foot voltage at 260V. Nope, no voltage protection there. I turned the Vivitar
off and was surprised to have it fire (apparently at full strength) as it was being removed from the shoe.
That last event led to an immediate glance to the YN560 III and realized that a light that should not be lit was glowing constant red. I tried to turn the speedlight off, but it was unresponsive. I removed the batteries in the hope that it would reset, but alas, when they were replaced, it would not start. The best it would muster was a very short and faint buzzing sound similar to the stepping motor that works the flash zoom.
(...cue the sound of taps playing softly in the distance...)
The flash firing created a significant current flow through the firing circuits of both flash with the Yongnuo taking the brunt of the punishment. Lesson learned...
Edit: As pointed out by @photoptimist below, the mechanism of when and how the damage was done is up for discussion. My description immediately above is probably not accurate, something I thought about after I wrote it.
Never put a high voltage flash in circuit with any device that it might kill!!! Edit: I have added a photo of the setup in a comment below for clarity...
https://www.pentaxforums.com/forums/125-flashes-lighting-studio/409444-new-w...ml#post5027307
Steve
(...$71 USD for a replacement YN560 III...now trying to figure out if that is a known behavior for the Vivitar...)
Last edited by stevebrot; 06-29-2020 at 08:39 PM.
Reason: Factual note