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06-28-2020, 10:24 PM - 7 Likes   #1
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A New Way To Do Serious Damage With A High Voltage Flash

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
06-28-2020, 11:27 PM   #2
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Been a long time since I owned any vintage flash gear but I have seen flashes trip when they are removed from flash shoes back in the day. I always got in the habit of turning the flash off before removing a flash from a shoe. Back then there wasnt the danger of frying anything but a full on flash off a powerful gun straight into your eyballs or someone elses wasnt very desirable.

Possibly the flash hot shoe connector shorted against the camera body work....dont know as I have never looked into it I only recall ai have seen this happen.

So yes...it may well have been an attribute of flashes back then.
06-28-2020, 11:28 PM   #3
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Um, sad as it may be, the Yongnuo can be easily replaced, I assume, but is there a reasonable chance that the vintage flash could have killed your K-3 (or whatever's topshoe that was), too?

At any rate, a rather chilling cautionary tale. Certainly appreciated that you share it.

Last edited by Madaboutpix; 06-29-2020 at 01:24 AM. Reason: Spelling.
06-29-2020, 12:48 AM   #4
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Sorry to hear you blitzed the Yongnuo, Steve At least you learned something and - better still - kindly shared the information for everyone's benefit. Some good has come from it, then - and I appreciate the knowledge, especially since I've been jonesing for a 283 since you mentioned getting one I was looking at some on eBay UK just yesterday...

06-29-2020, 02:48 AM   #5
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I don't know about the 283 but the 285 has the manual flash trigger button on the "ankle" of the foot which makes it easy to set off the flash when taking it on or off. That said I've had flashes go off when inserting them or removing them from the shoe. After doing this a few times you quickly get into the habit powering off the flash before mounting or dismounting.

Sorry to hear the speedlight got fried.
06-29-2020, 05:17 AM - 1 Like   #6
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Sorry for your loss!

Two minor quibbles:

1) the amount of current in the hotshoe contacts of an old flash is never high even though the voltage is high. The hotshoe circuit essentially connects the high voltage capacitor to an electrode on the OUTSIDE of flash tube which creates a high-voltage field in the tube sufficient to start the breakdown of the xenon inside the tube. The amount of current is negligible and short-lived (just enough to charge the capacitance of the trigger circuit) because that circuit includes the glass envelope of the tube (a near-infinite resistance). That's why accidentally touching bare wires going to or from the hotshoe with your fingers will give a little sting but not create a burn or risk of electrocution.

2) Digital circuits can be killed by voltage alone without much current involved. The junctions of transistors inside chips can be very thin in order to create sensitive, high-speed circuits. Voltages as low a 20 volts can instantly destroy the junction even if the current is small and short lived.
06-29-2020, 06:01 AM - 2 Likes   #7
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QuoteOriginally posted by stevebrot Quote
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...

Never put a high voltage flash in circuit with any device that it might kill!!!


Steve

(...$71 USD for a replacement YN560 III...now trying to figure out if that is a known behavior for the Vivitar...)
Sounds like you need to contact an attorney and start a class action lawsuit! The attorney representing the woman suing Ricoh USA would be a great attorney for this one!!
06-29-2020, 06:47 AM   #8
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Sorry to hear about the loss. A Yongnuo may be reasonably priced compared to an OEM flash, but it is hardly cheap.

And thanks for sharing this hard earned lesson.

06-29-2020, 09:12 AM   #9
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QuoteOriginally posted by Astro-Baby Quote
I always got in the habit of turning the flash off before removing a flash from a shoe.
That is my practice as well and the Vivitar 283 was definitely turned off.

QuoteOriginally posted by Madaboutpix Quote
Um, sad as it may be, the Yongnuo can be easily replaced, I assume, but is there a reasonable chance that the vintage flash could have killed your K-3 (or whatever's topshoe that was), too?
I am going to add a photo of the setup for the benefit of those who are unfamiliar with the 5P adapters. Thankfully, there was no camera in the mix. My mistake was was to forget that the two flashes were on the same circuit and to also forget that I had seen the 283 fire on removal when turned off before. Strangely, it is one of those flash that maintain voltage to the foot even when turned off. My Sigma EF-610 DG Super also keeps its foot high for whatever reason, but does not fire if turned off.


Steve
06-29-2020, 09:48 AM   #10
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QuoteOriginally posted by photoptimist Quote
Sorry for your loss!

Two minor quibbles:

1) the amount of current in the hotshoe contacts of an old flash is never high even though the voltage is high. The hotshoe circuit essentially connects the high voltage capacitor to an electrode on the OUTSIDE of flash tube which creates a high-voltage field in the tube sufficient to start the breakdown of the xenon inside the tube. The amount of current is negligible and short-lived (just enough to charge the capacitance of the trigger circuit) because that circuit includes the glass envelope of the tube (a near-infinite resistance). That's why accidentally touching bare wires going to or from the hotshoe with your fingers will give a little sting but not create a burn or risk of electrocution.

2) Digital circuits can be killed by voltage alone without much current involved. The junctions of transistors inside chips can be very thin in order to create sensitive, high-speed circuits. Voltages as low a 20 volts can instantly destroy the junction even if the current is small and short lived.
I understand your quibbles. I don't have the means to measure the transient current through the flash foot, but it has long been my understanding that the fault with the vintage flash is that the discharge circuit runs through the foot (no isolation from the trigger circuit) and therefore the camera also in the same manner as a flash bulb.

On your second point, you are very correct. I have spent quite a bit of time pondering how this might have happened. I would have expected that any damage would have been done prior to the discharge based on current leakage through the junction. I do know that the wireless status light on the YN560 (a very bright red LED) was not lit before the accident (wireless was turned off to allow voltage to the foot). The display was still working and the power light was still on, but with the flash unresponsive. After battery removal/replacement, all display was dead. On the side, I would have expected the YN560 would have a degree of hardening since these units are sometimes deployed in wired studio settings. A schematic for the YN560 might hold the clue as might a schematic of the Viv 283.

Regardless of mechanism, the bottom line is to not put these older flash in a circuit with other devices without isolating the foot.


Steve
06-29-2020, 09:50 AM   #11
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QuoteOriginally posted by stevebrot Quote
My mistake was was to forget that the two flashes were on the same circuit and to also forget that I had seen the 283 fire on removal when turned off before. Strangely, it is one of those flash that maintain voltage to the foot even when turned off. My Sigma EF-610 DG Super also keeps its foot high for whatever reason, but does not fire if turned off.
Interestingly, I'm almost certain my modern-but-basic Powerextra DF-400 flash has fired on removal from a radio trigger even when switched off. It was a while back, but I remember being quite surprised. It hasn't been a consistent thing...
06-29-2020, 08:36 PM   #12
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Here is how things were set up when the 283 snuffed the YN560 III. No camera was attached.




Both flash were turned on and I was measuring the center pin voltage relative to the shoe rail on the Hot-Shoe Adapter F before turning the 283 off and sliding it off of the adapter. The 283 discharged as it was being removed and it was immediately after that I noticed the Yongnuo was not doing well. It may not be clear, but the cord placed the center contacts of two flash in common on an open circuit with the same true for the foot rails.


Steve
06-29-2020, 09:46 PM - 1 Like   #13
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QuoteOriginally posted by Frank Back Quote
Why would you use dangerous old gear? Nostalgia? I suppose you could find leaded paint and asbestos insulation, but why? The good old days?

And yeah, a parallel circuit has a common voltage.
Good to meet you, Frank. I use dangerous old gear for tasks for which they are useful and for which my newer stuff offers no advantage. As for the common voltage on a parallel circuit, I learned that in grade six. The lesson of this thread is that it is easy to screw up. FWIW, there are a fair number of folk around here that use gear that we've been shooting with for the last 40 years or so; in some cases the last 50 or 60 years or so.
Steve

(...Boriscleto? )

Last edited by stevebrot; 06-30-2020 at 09:20 AM.
06-30-2020, 04:57 AM - 2 Likes   #14
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QuoteOriginally posted by stevebrot Quote
I understand your quibbles. I don't have the means to measure the transient current through the flash foot, but it has long been my understanding that the fault with the vintage flash is that the discharge circuit runs through the foot (no isolation from the trigger circuit) and therefore the camera also in the same manner as a flash bulb.
The discharge from the capacitor through the flash tube does not go through the hot shoe.

Instead, what goes through the hot shoe (or PC cord) and thus through the camera is less than 0.1% of the flash's power. The hot shoe of an old flash does carry the full voltage of the flash but it connected to a high-resistance, tiny-capacitance circuit. (Notice the 7000:1 ratio between the 160F main capacitor and the 0.022F firing circuit capacitor plus the 1 megohm resistor in the firing circuit )



P.S. Switching the flash OFF does not make the hot shoe safe on a lot of old flashes. The on-off switch only controls battery power to the flash-charger circuit, not capacitor power to the hot shoe & flash tube circuit. (Try turning on the 283, letting it fully charge, then switch it off and measure the shoe voltage. The shoe voltage will probably remain quite high for at least several minutes and maybe longer.)

Last edited by photoptimist; 06-30-2020 at 06:24 AM.
06-30-2020, 09:15 AM - 2 Likes   #15
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QuoteOriginally posted by photoptimist Quote
The hot shoe of an old flash does carry the full voltage of the flash ...
Some of us use the original production (Japanese manufactured) of the Vivitar 283, and although the current through the hot show is limited the trigger voltage of 260-280 volts on the shoe is indeed the same as that on the main flash capacitor. My 283s have been modified to use an optoisolated 5 volts on the shoe.
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