K-7 Sync Port: Max Trigger Voltage?

zosxavius · 09-13-2013, 09:26 AM

I have a good old vivitar 272 here I want to make my new on camera flash. Its the one that takes 2 9v batteries. According to the strobist, the trigger voltage was measured at around 260v. I know that this will indeed fry my K-7s hotshoe. Reading through some comments on here and dpreview it seems that the k20d's sync port was protected against high voltage triggers. John Carlson mentions it in his video on Pentaxian. I'm assuming that the k-7 would include similar protections. Another thread at least confirmed that the sync port is on a separate circuit than the hotshoe. I know about the wein adapter and there is a photodiox adapter that is even cheaper ($12) that supposedly works. My original idea was to get an old sunpak flash grip that has a broken flash and repurpose it as another forum user has done. I would prefer not to use an adapter if I know for a fact that the sync port won't fry. The canon 5d mk2 I use for my job has a max trigger voltage of 250v I believe, but I've read that the k-7 is good to 300v and that people have used vivitar 283s with a trigger voltage of 260v on the port and the camera didn't fry. It seems silly to buy a safe adapter if the camera has one built in. I could put it on a wireless receiver too, but on a camera that whole setup sounds clunky to say the least. I'm tempted to try this on my older semi-retired k-7. Anyone have any thoughts? I know some people out there can confirm if I should be safe to use the port or not. I use old high voltage studio strobes on the 5dmk2 with a wein, but I have in fact used the port on that camera and it survived while pushing close to the 250v rated maximum.

stevebrot · 09-18-2013, 12:44 PM

Originally posted by zosxavius

Reading through some comments on here and dpreview it seems that the k20d's sync port was protected against high voltage triggers.

The K20D does not have a sync port, so I guess that qualifies as the ultimate protection.

Edit: I have been properly corrected. The K20D does indeed have a PC flash sync on the left side of the body, though the manual has a stern warning against exposing the camera to high voltage flash units through that port.End edit

Seriously though, yours is a very good question. I generally would have been of the assumption that the PC socket of your K-7 should be safe, though on second thought there is no real reason to believe that to be true. I would expect that the PC socket would support at least the same voltage as the hot shoe (about 25V). You can measure the flash voltage directly with a voltmeter. I would suggest that rather than relying on various Internet accounts.

Steve

(Your 5DMk2 supports 250V? That is a marked improvement over my Canon digital which only supports 6V. Great way to sell Canon Speedlights.)

zosxavius · 09-19-2013, 04:53 PM

Originally posted by stevebrot

The K20D does not have a sync port, so I guess that qualifies as the ultimate protection.

Seriously though, yours is a very good question. I generally would have been of the assumption that the PC socket of your K-7 should be safe, though on second thought there is no real reason to believe that to be true. I would expect that the PC socket would support at least the same voltage as the hot shoe (about 25V). You can measure the flash voltage directly with a voltmeter. I would suggest that rather than relying on various Internet accounts.

Steve

(Your 5DMk2 supports 250V? That is a marked improvement over my Canon digital which only supports 6V. Great way to sell Canon Speedlights.)

Yuh the 5dmk2 supports 250V or so at the port. I think the hotshoe is limited to less than 10V or so. I'll ask pentax and see if I can get an official answer. The Vivitar 272 was measured by someone at 240V, so it is certainly high voltage.

**maxfield_photo** · 09-24-2013, 03:34 PM

Originally posted by stevebrot

The K20D does not have a sync port, so I guess that qualifies as the ultimate protection.

It most definitely does have a sync port.

stevebrot · 09-24-2013, 03:43 PM

Originally posted by maxfield_photo

It most definitely does have a sync port.

You are indeed correct. I will amend my previous post.

The manual also warns against high voltage flash units for that port. Too bad Pentax does not give a definition of high voltage.

Steve

zosxavius · 09-26-2013, 02:37 PM

Aaaaaand 4 days later I get an answer. (pentax usa is really on the ball!)

"Hi Zos,

This question has come up on a fairly regular basis over the years. While the PC sync port on these cameras (K-7, K-5, K-5 II) does have a degree of built-in circuit protection, we do not have an official (or unofficial) safe trigger voltage figure we can provide. However, there are inexpensive 3rd-party products widely available which can provide additional protection for the camera's circuitry. These devices work by reducing the flash trigger voltage to 6 volts or less. Likewise, we will occasionally receive a question regarding the safe hotshoe trigger voltage for our DSLRs. In this case, we can only state that PENTAX flash units (including older PENTAX flashes) are safe to use with our DSLRs. Hope this helps,"

I don't understand why they can't just put a spec out. So frustrating actually. Canon and Nikon both rate their sync ports.

PS: From what I have gathered the hot shoe is safe up to 25-30V according to various sources. Anyone have a k-7 they want to lend me to test 250V with on the sync port?

wombat2go · 09-26-2013, 03:17 PM

I have just failed the flash trigger on my Olympus E-PL1.
I was using on the hotshoe an old Pentax AF 16 which i have measured with a trigger voltage of +5V or so.
I accidentally pulled the flash off the camera while both the camera and flash were powered up.
I might have pressed the flash test button at the same time, or maybe pressed the shutter release, any way the flash went off.
Now the pull down driver in the camera has failed to a short circuit.

zosxavius · 09-26-2013, 03:34 PM

Originally posted by wombat2go

I have just failed the flash trigger on my Olympus E-PL1.
I was using on the hotshoe an old Pentax AF 16 which i have measured with a trigger voltage of +5V or so.
I accidentally pulled the flash off the camera while both the camera and flash were powered up.
I might have pressed the flash test button at the same time, or maybe pressed the shutter release, any way the flash went off.
Now the pull down driver in the camera has failed to a short circuit.

Oh no!

I've had flashes pop as I take them out of the hotshoe on my k-5 and k-7. Never had one short circuit. That really sucks.

wombat2go · 09-26-2013, 03:45 PM

It is not the end for the E-PL1 because it has a very well controlled onboard flash which still works.

We talk about the steady state flash trigger voltage and measure it etc, and use them if the voltage is around 5V.
But now I wonder about the transient voltage on the pin on those old flashes when the flash is triggered by the test button, when the camera driver is off and therefore vulnerable.
I will try to measure the transient next time I have the oscilloscope on the bench.
When these old flashes were designed, the cameras just had contacts and a transient was not an issue.

09-13-2013, 09:26 AM	#1
zosxavius Veteran Member Join Date: Jan 2012 Location: Somewhere, USA Photos: Gallery Posts: 458	K-7 Sync Port: Max Trigger Voltage? I have a good old vivitar 272 here I want to make my new on camera flash. Its the one that takes 2 9v batteries. According to the strobist, the trigger voltage was measured at around 260v. I know that this will indeed fry my K-7s hotshoe. Reading through some comments on here and dpreview it seems that the k20d's sync port was protected against high voltage triggers. John Carlson mentions it in his video on Pentaxian. I'm assuming that the k-7 would include similar protections. Another thread at least confirmed that the sync port is on a separate circuit than the hotshoe. I know about the wein adapter and there is a photodiox adapter that is even cheaper ($12) that supposedly works. My original idea was to get an old sunpak flash grip that has a broken flash and repurpose it as another forum user has done. I would prefer not to use an adapter if I know for a fact that the sync port won't fry. The canon 5d mk2 I use for my job has a max trigger voltage of 250v I believe, but I've read that the k-7 is good to 300v and that people have used vivitar 283s with a trigger voltage of 260v on the port and the camera didn't fry. It seems silly to buy a safe adapter if the camera has one built in. I could put it on a wireless receiver too, but on a camera that whole setup sounds clunky to say the least. I'm tempted to try this on my older semi-retired k-7. Anyone have any thoughts? I know some people out there can confirm if I should be safe to use the port or not. I use old high voltage studio strobes on the 5dmk2 with a wein, but I have in fact used the port on that camera and it survived while pushing close to the 250v rated maximum.

09-18-2013, 12:44 PM	#2
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by zosxavius Reading through some comments on here and dpreview it seems that the k20d's sync port was protected against high voltage triggers. The K20D does not have a sync port, so I guess that qualifies as the ultimate protection. Edit: I have been properly corrected. The K20D does indeed have a PC flash sync on the left side of the body, though the manual has a stern warning against exposing the camera to high voltage flash units through that port.End edit Seriously though, yours is a very good question. I generally would have been of the assumption that the PC socket of your K-7 should be safe, though on second thought there is no real reason to believe that to be true. I would expect that the PC socket would support at least the same voltage as the hot shoe (about 25V). You can measure the flash voltage directly with a voltmeter. I would suggest that rather than relying on various Internet accounts. Steve (Your 5DMk2 supports 250V? That is a marked improvement over my Canon digital which only supports 6V. Great way to sell Canon Speedlights.) Last edited by stevebrot; 09-24-2013 at 03:46 PM.

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09-19-2013, 04:53 PM	#3
zosxavius Veteran Member Join Date: Jan 2012 Location: Somewhere, USA Photos: Gallery Posts: 458 Original Poster	Originally posted by stevebrot The K20D does not have a sync port, so I guess that qualifies as the ultimate protection. Seriously though, yours is a very good question. I generally would have been of the assumption that the PC socket of your K-7 should be safe, though on second thought there is no real reason to believe that to be true. I would expect that the PC socket would support at least the same voltage as the hot shoe (about 25V). You can measure the flash voltage directly with a voltmeter. I would suggest that rather than relying on various Internet accounts. Steve (Your 5DMk2 supports 250V? That is a marked improvement over my Canon digital which only supports 6V. Great way to sell Canon Speedlights.) Yuh the 5dmk2 supports 250V or so at the port. I think the hotshoe is limited to less than 10V or so. I'll ask pentax and see if I can get an official answer. The Vivitar 272 was measured by someone at 240V, so it is certainly high voltage.

09-24-2013, 03:34 PM	#4
maxfield_photo Site Supporter Join Date: Mar 2011 Location: Cincinnati, OH Posts: 1,216	Originally posted by stevebrot The K20D does not have a sync port, so I guess that qualifies as the ultimate protection. It most definitely does have a sync port.

09-24-2013, 03:43 PM	#5
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by maxfield_photo It most definitely does have a sync port. You are indeed correct. I will amend my previous post. The manual also warns against high voltage flash units for that port. Too bad Pentax does not give a definition of high voltage. Steve

09-26-2013, 02:37 PM	#6
zosxavius Veteran Member Join Date: Jan 2012 Location: Somewhere, USA Photos: Gallery Posts: 458 Original Poster	Aaaaaand 4 days later I get an answer. (pentax usa is really on the ball!) "Hi Zos, This question has come up on a fairly regular basis over the years. While the PC sync port on these cameras (K-7, K-5, K-5 II) does have a degree of built-in circuit protection, we do not have an official (or unofficial) safe trigger voltage figure we can provide. However, there are inexpensive 3rd-party products widely available which can provide additional protection for the camera's circuitry. These devices work by reducing the flash trigger voltage to 6 volts or less. Likewise, we will occasionally receive a question regarding the safe hotshoe trigger voltage for our DSLRs. In this case, we can only state that PENTAX flash units (including older PENTAX flashes) are safe to use with our DSLRs. Hope this helps," I don't understand why they can't just put a spec out. So frustrating actually. Canon and Nikon both rate their sync ports. PS: From what I have gathered the hot shoe is safe up to 25-30V according to various sources. Anyone have a k-7 they want to lend me to test 250V with on the sync port?

09-26-2013, 03:17 PM	#7
wombat2go Veteran Member Join Date: Jan 2010 Location: Michigan Photos: Gallery Posts: 2,207	I have just failed the flash trigger on my Olympus E-PL1. I was using on the hotshoe an old Pentax AF 16 which i have measured with a trigger voltage of +5V or so. I accidentally pulled the flash off the camera while both the camera and flash were powered up. I might have pressed the flash test button at the same time, or maybe pressed the shutter release, any way the flash went off. Now the pull down driver in the camera has failed to a short circuit.

09-26-2013, 03:34 PM	#8
zosxavius Veteran Member Join Date: Jan 2012 Location: Somewhere, USA Photos: Gallery Posts: 458 Original Poster	Originally posted by wombat2go I have just failed the flash trigger on my Olympus E-PL1. I was using on the hotshoe an old Pentax AF 16 which i have measured with a trigger voltage of +5V or so. I accidentally pulled the flash off the camera while both the camera and flash were powered up. I might have pressed the flash test button at the same time, or maybe pressed the shutter release, any way the flash went off. Now the pull down driver in the camera has failed to a short circuit. Oh no! I've had flashes pop as I take them out of the hotshoe on my k-5 and k-7. Never had one short circuit. That really sucks.

09-26-2013, 03:45 PM	#9
wombat2go Veteran Member Join Date: Jan 2010 Location: Michigan Photos: Gallery Posts: 2,207	It is not the end for the E-PL1 because it has a very well controlled onboard flash which still works. We talk about the steady state flash trigger voltage and measure it etc, and use them if the voltage is around 5V. But now I wonder about the transient voltage on the pin on those old flashes when the flash is triggered by the test button, when the camera driver is off and therefore vulnerable. I will try to measure the transient next time I have the oscilloscope on the bench. When these old flashes were designed, the cameras just had contacts and a transient was not an issue.