Firing large studio strobes with a old-time PC cord on Nikon 750: I've been shooting with AC powered studio strobes forever and I've never had a problem with excess voltage. Over the...

Bob Werre

I've been shooting with AC powered studio strobes forever and I've never had a problem with excess voltage. Over the years I've generally used either IR or radio control for the connection. However once in a while for a simple shot, I find the old coiled PC cord the easiest. I was going to purchase a Nikon AS-15 connector, but they warn about excess voltage. Has anybody had any problem with 'frying' their camera with excess voltage? I usually use Dynatrol studio strobes and occasionally a 2400WS Comet pack.

twowindsbear

Why risk it? Use the interface device!

User ID

Wein and others make something similar to the AS15 but including voltage reduction circuits.

BTW have meter test the trigger voltage of your flash rigs ? Some are OK.

There’s a lotta worry wart belief that 10v, or even 6v, is the limit. I go with anything under 30v. Someone is going to quote their user guide saying 9v or whatever.

Basically just avoid high voltage, or even “medium high” voltage. Thaz how I figgered ”nothing above the twenties”. If I had shunned all the flashes that trigger in the twenties, my options would’ve been next to nothing. “Twenty something” is truly NOT a high trigger voltage. Again, meter check your gear.

Haydon

Do some digging and find out the voltage on your studio strobes. Otherwise a shortcut could make your session short and costly.

TriX Loc: Raleigh, NC

You can use a meter to check the trigger voltage of the strobe, but a DVM isn’t fast enough in terms of response to record the max voltage of the trigger pulse - you really need a storage oscilloscope to see it. Without seeing a schematic of the camera, and knowing the specs of the semiconductor device doing the switching (modern cameras typically use a device rather than plain contacts), there’s no way to know if it’s safe except to find out the hard way, which can be a very expensive mistake. Here’s a link to a list of typical strobe trigger voltages: https://www.botzilla.com/photo/strobeVolts.html
If your strobe is included, compare it to the max spec of your camera. If it’s not and you don’t have a DSO to get an accurate measurement, I wouldn’t risk it - a trigger is a lot cheaper than the main board in the camera.

BebuLamar

TriX wrote:

You can use a meter to check the trigger voltage o... (show quote)

There is no spike voltage in the trigger voltage. In fact when the flash is ready the voltage is at the highest. When the flash fires the voltage drops on some flashes and some not but not raises. The one that doesn't drop has low voltage. So measure the voltage when the flash is ready. If it's 12V or so it's safe. The D750 is rated at 250V but no I wouldn't use with any flash near that.

TriX Loc: Raleigh, NC

BebuLamar wrote:

There is no spike voltage in the trigger voltage. In fact when the flash is ready the voltage is at the highest. When the flash fires the voltage drops on some flashes and some not but not raises. The one that doesn't drop has low voltage. So measure the voltage when the flash is ready. If it's 12V or so it's safe. The D750 is rated at 250V but no I wouldn't use with any flash near that.

Have you actually visualized/recorded the signal on a scope? If there is any inductance in the trigger circuit, when the field collapses, there will be a spike. I don’t think either of us has a schematic for the strobes in question, but here’s a typical strobe trigger circuit. Note the trigger transformer. When the field in the transformer collapses, there will certainly be a spike. That’s exactly why there are suppressor diodes across relay coils - to suppress the reverse polarity pulse generated when the field collapses. In the circuit shown, the reverse pulse commutates the SCR, but does any of it appear on the gate or propagate back through the circuit? No way to know without actually looking at the input. It’s just not expensive to be safe and a lot more convenient than a cord. I use an inexpensive Youngnuo receiver (<$20) to trigger my old Novatron strobes. I use the same on-camera RF transmitter that I use to trigger my flashes.

roxiemarty Loc: Florida

Wein safe sync. Used one for years with my ancient Novatron studio strobes. Now I've gone wireless with Odin radio slaves. This image from Google. Works great with cord.

Screamin Scott Loc: Marshfield Wi, Baltimore Md, now Dallas Ga

A couple of points to make. A flash with a high trigger voltage won't instantly fry most circuits... It's more of a gradual thing leading to the failure of the circuit. Most "dedicated" flash units are safe. It's primarily the older "single" pin units that can be an issue although I use interchangeable modules on my ring lights that revert back to the single pin on the foot. Saves me from having to tape over extra contacts. Bottom line is to test the units though...

Nicholas DeSciose

This is the best advice

rochephoto

I've had a large studio for over 30yrs. There is always a risk of a voltage spike in the sync carrier signal with any brand of strobe if there is an equipment malfunction. On the other hand, there are a couple of strobe brands of strobe that are known to have higher voltage sync carrier signals. Most notably are Speedotron and Norman. The real question to ask is what's cheaper, replacing your camera or a couple of radio slaves?

GoofyNewfie Loc: Kansas City

Bob, since the D750 doesn’t have a PC connection, you’ll have to get something anyway.
Might as well spring for the Wein Safe-Sync as roxiemarty above suggested, if you want to use a cord.
I’m sold on radio personally.

I miss using those Comet packs.
Such a nice system!
Speedotron was well built but I got a hernia using them!
Never heard of Dynatrol, is that a spell-correct of Dynalite?

henryp Loc: New York, NY

Bob Werre wrote:

I was going to purchase a Nikon AS-15 connector, but they warn about excess voltage.

The AS-15 is a handy gadget but it's just an adapter - no filter. Look at the Wein Safe-Sync Hot Shoe to Hot Shoe with PC for a similar adapter with a voltage filter: https://bhpho.to/2D5azz9

Another option is a Paramount cord with a filter built in: https://bhpho.to/2CV6sp5

GoofyNewfie Loc: Kansas City

henryp wrote:

The AS-15 is a handy gadget but it's just an adapter - no filter. Look at the Wein Safe-Sync Hot Shoe to Hot Shoe with PC for a similar adapter with a voltage filter: https://bhpho.to/2D5azz9

Another option is a Paramount cord with a filter built in: https://bhpho.to/2CV6sp5

Interesting.
Didn’t know about the cord.

rochephoto

I've heard good and bad about the cord filters...