PC-cord triggering of multiple flashes

mmerig · Apr 11, 2017

Two flash units connected via PC-cords will not fire together. Here is what I have and tried.

Flash units: Nikon SB-29, Vivitar 265

Connectors: PC cords and a Kalt-3-way terminal

Triggers: Synchro-Compur leaf shutter in a Schneider-Kreuznach 210 mm, Nikon F or Nikon F3 via PC terminal

Both flashes are switched to Manual. The Nikon SB-29 always fires, whether the Vivitar is connected or not. The Vivitar only fires when the Nikon SB-29 is not connected, and this happens with all three triggers. The cords and three-way connector seem fine.

I plan on using them on a home-made copy stand, and these are the two units I have. Is the Vivitar incompatible? The manual for either unit mentions using them with pc-cords along with other flash units.
This is such a simple set-up, it's hard to imagine what could be wrong.

MattKing · Apr 11, 2017

Can you put a slave trigger on the Vivitar?
Have you tried switching the positions on the three-way connector?

Ian Grant · Apr 11, 2017

MattKing said:
Can you put a slave trigger on the Vivitar?
Have you tried switching the positions on the three-way connector?

He says PC cords so he should look for some slaves, that's the easiest way, they can be found quite cheaply. Some flashes use the trigger voltage the other way so it could be a clash here between the two makes. Trigger one by the cord the other by a slave.

Ian

M Carter · Apr 11, 2017

The Wein slaves are usually numerous on eBay, but a little pricey. I got a couple Cowboy Studio/China imports, and they work fine, twelve bucks. Hot shoe and PC connector and 1/4-20 socket. I think they also sell one for $2 less that only has the hot shoe.

Chan Tran · Apr 11, 2017

Connect the Nikon to the sync cord but not the Vivitar. Then connect the Vivitar. Does the Vivitar fires immediately with out being triggered by the camera? If so the Nikon made the Vivitar fires all the time and thus it only fires once.

mmerig · Apr 11, 2017

Thanks for the advice from all of you.

Ian is onto something -- although the voltage polarity is the same (positive on the center connection within the PC jack), the magnitude is vastly different. The Nikon SB-29 has about 5 volts, the Vivitar about 160. There may be a zener diode or something in the SB-29 to protect the unit from unsuspecting people like me that would hook-up an old flash unit to it, and the zener drops the system voltage too low to trip the Vivitar in this case.

Regarding Chan Tran's advice: when I connected the Vivitar after first connecting the Nikon, the Vivitar did not fire. Also, when both are connected, and I push the little red trigger button on the Vivitar, the Nikon flashes but not the Vivitar. This is not surprising, as the red button substitutes for the shutter.

Has the trigger-voltage standard (if there is one) stabilized? For example, will a newer (say post-1990) Nikon flash unit have the same trigger voltage as a Nikon SB-29?

I'll search, but if off-hand anyone knows of a spec. table that shows trigger voltages and polarity by flash model or brand, that would be helpful. I'd like to get a TTL flash unit anyway, to replace the Vivitar, that would work with my F3.

I'd rather not go with a slave unit if I can get away with it.

Thanks again.

Leigh B · Apr 11, 2017

You should NEVER connect multiple flashes together unless they're identical units (make and model).

Connecting dissimilar units can results in bright lights and loud noises

(NOT the kind of bright lights you want).

Leigh

M Carter · Apr 11, 2017

mmerig said:
I'd rather not go with a slave unit if I can get away with it.

Man, they're about the handiest things on earth next to back-scratchers. A stubby little PC cord, or use a longer cord for flashes that may not pick up the master flash and get the slave right where you need it. I have 'em snaking out of speedo packs for complex setups. And I can keep 2 or 3 in a film vial.

Maybe you're thinking of something different, but seems to me they would beat wiring strobes together by a mile?

John Koehrer · Apr 11, 2017

The newer 283's/285's use a lower trigger voltage. Like Ian suggests though the slave may work best for you.
Most of the optical slaves work best with common room light but may not work well with a brightly lit room.

I've got a couple, If you'd like one I'd mail it for $7.00

They both fit a standard hot shoe or a 1/4" thread and have a hot shoe connection and a PC connection
One is Wein and one is Lenmar I'll check them out before shipping,. The Lenmar is
cosmetically better than the Wein.

RalphLambrecht · Apr 12, 2017

mmerig said:
Thanks for the advice from all of you.

Ian is onto something -- although the voltage polarity is the same (positive on the center connection within the PC jack), the magnitude is vastly different. The Nikon SB-29 has about 5 volts, the Vivitar about 160. There may be a zener diode or something in the SB-29 to protect the unit from unsuspecting people like me that would hook-up an old flash unit to it, and the zener drops the system voltage too low to trip the Vivitar in this case.

Regarding Chan Tran's advice: when I connected the Vivitar after first connecting the Nikon, the Vivitar did not fire. Also, when both are connected, and I push the little red trigger button on the Vivitar, the Nikon flashes but not the Vivitar. This is not surprising, as the red button substitutes for the shutter.

Has the trigger-voltage standard (if there is one) stabilized? For example, will a newer (say post-1990) Nikon flash unit have the same trigger voltage as a Nikon SB-29?

I'll search, but if off-hand anyone knows of a spec. table that shows trigger voltages and polarity by flash model or brand, that would be helpful. I'd like to get a TTL flash unit anyway, to replace the Vivitar, that would work with my F3.

I'd rather not go with a slave unit if I can get away with it.

Thanks again.

the slaves are the best way to protect your camera from a flash frying your shutter contacts

benjiboy · Apr 12, 2017

Using several flashguns with a "Sputnik" multi sync lead flash connector can damage your cameras flash sync ability, the cheapest and best method to use is to plug one flash into your camera with a sync. lead and buy a peanut optical slave trigger https://www.bhphotovideo.com/c/product/764705-REG/Nisha_FSU_Flash_Slave_Unit.htmlfor each additional flash you use.

AgX · Apr 12, 2017

I am aware of the voltage issue.

But in hindsight, I do not remember ever seen a respective hint in the past in catalogs offering multiple-connectors PC-plugs, nor on the package.

M Carter · Apr 12, 2017

I have a little plastic bar, maybe 3/4" x 1/8" - it's just 4 or 5 PC connectors wired together. Don't know if they're still made, but the PC connector being such a crap connector anyway, I never used it much and just got more peanut slaves.

ac12 · Apr 12, 2017

Depending on the environment (other flashes) I will use one of the following setups.

with no other flashes in the area
- primary flash (wire or RF controlled), secondary flashes (optical slaves triggered by the primary flash)
- camera flash (with shield to prevent lighting the subject), primary and secondary flashes (optical slaves triggered by the camera flash)
with other flashes in the area
- all flashes (RF controlled)

I trust my optical slaves more than my hobby priced RF flash triggers.

mmerig · Apr 13, 2017

Leigh B said:
You should NEVER connect multiple flashes together unless they're identical units (make and model).

Connecting dissimilar units can results in bright lights and loud noises

(NOT the kind of bright lights you want).

Leigh

Thanks for the comments. Leigh's advice is the safe bet, but "NEVER" is a bit strong, although I can imagine a polarized capacitor exploding high under reverse-polarity voltage.

Regarding slaves, the reason I prefer PC-cords over them is that the flash units and camera will be less than 1 foot from each other (on a copy stand, please see original post). A slave may work here, but the weak link is the Vivitar flash unit itself (the hot shoe is cracked, and it does not work with the Nikon SB-29). So in the long run, a more modern unit may be better than just adding in a slave. I tend to be conservative when buying equipment - the F3 and SB-29 are the most modern, sophisticated gear that I own.

The manual for the Nikon SB-29 lists several Nikon flash models that can be used with it for multiple flash set-ups. There is no warning about voltage, but with too many units (like 10 to 20, depending on the model), there will be too much current draw and the circuitry has to be re-set by taking the unit off the camera and replacing it. There is no dire warning about mixing flash units in either instruction manual (Nikon SB-29 or Vivitar 265), and the Nikon F3 manual has no warning about sync cord voltages. The Vivitar 265 and F3 are roughly contemporary, so it is conceivable that many people used them together. The F3 probably has a simple switch rather than a thyristor which would have a break-down voltage. The Synchro-compur shutter I plan on using just has a switch.

There is an internet site on multiple flashes and trigger voltages, etc.

http://dpanswers.com/content/genrc_flash_measuretv.php

and a listing of trigger voltages is here:

http://dpanswers.com/roztr/volt_finder.php

The above site warns about high voltages potentially ruining a slave as well as a camera, but the voltage has to be quite high -- like 250, and the cameras at stake are modern digital ones. This probably applies to modern film cameras too, with a thyristor in the synch circuitry. I still think that staying with the 24-volt limit on newer cameras is prudent. Ralph Lambrecht has a little bit on this in his and Chris Woodhouse's book (Way Beyond Monochrome) -- thank you for this and such a wonderful book in general.

John_Nikon_F · Apr 13, 2017

Pick up a couple SB-22 (non-ringlight version of the SB-29) units, then you can do your experiment. Leave the 265 for use as a solo flash on the F or the view camera, and leave the SB-29 for use with an AS-17 on the F3 for macro work. The SB-22 is similar in power to the 265 (GN of 82, instead of 80) and, like the 265, cheap on the market.

If you really want to use the old 265, get a Wein SafeSync, even though your cameras should handle up to 200 volts without problems. But, then you'd be less likely to blow up whichever Nikon flash you use. The 265 actually predates the F3 by at least a couple years, so it's more an F2 contemporary.

-J

AgX · Apr 13, 2017

mmerig said:
There is an internet site on multiple flashes and trigger voltages, etc.

http://dpanswers.com/content/genrc_flash_measuretv.php

It says

To check an unknown trigger voltage, you'll need a digital multimeter.

To the contrary.
One needs an analogue multimeter, as these always have a high resistance. The leak current through a digital meter is likely to trip the flash.

AgX · Apr 13, 2017

benjiboy said:
a "Sputnik" multi sync lead flash connector

For a moment I was puzzled by the "brand", but then I got the point...
Well worded.

benjiboy · Apr 13, 2017

AgX said:
For a moment I was puzzled by the "brand", but then I got the point...
Well worded.

It's not a brand name, that's what we used to call them in my photo store because that's what they looked like.

AgX · Apr 13, 2017

Yes, well worded. (Only that younger people likely would not understand it, but here at Apug we are mostly between ourselves...)

Do you remember any warnings?

mmerig · Apr 13, 2017

AgX said:
It says

To the contrary.
One needs an analogue multimeter, as these always have a high resistance. The leak current through a digital meter is likely to trip the flash.

Digital multimeters are okay to use for trigger voltages on flash units. Their input impedance (or resistance if dealing with DC, as here) is in the several mega-ohm range, and typically constant across voltage. My analog, solid-state meter, for example, is 20K ohms per volt -- much lower than the digital version. This resistance was still not low enough to trip the Vivitar. Perhaps AgX meant a vacuum tube voltmeter? These have input impedance comparable to a digital multimeter, but they are more robust to high current, high voltage surges - not a problem with flash unit trigger circuits.

Thanks for the model recommendation, John. I might try a Nikon SB16A along with the SB29. Another Vivitar 265 could work, too. These are all quite inexpensive.

AgX · Apr 13, 2017

My personal experience is that my analogue multimeter works, whereas my digital one (manufacturer re-checked) trips flashes.
Maybe I was generalizeng, but my experiences coincided with respective advises I read.
(Wikipedia says the standard for digital meters is 10MOhm, though with large variation.)

Leigh B · Apr 13, 2017

mmerig said:
Digital multimeters are okay to use for trigger voltages on flash units. Their input impedance (or resistance if dealing with DC, as here) is in the several mega-ohm range, and typically constant across voltage.

The standard input resistance for amplified meters is 10 Megohms, and has been for many decades.
This includes modern digital meters and older vacuum tube voltmeters (VTVMs).

Analog meters were available in 1,000 ohms/volt and 20,000 ohms/volt sensitivities.
The 20,000 opv meter on the 500 volt range has an input resistance of 10 Megohms.

But 10 Megohms may be low enough to trigger a flash.

I used to be a warranty service station for Novatron studio strobes.
I had to build a special meter system to read the trigger voltage because all of my fancy voltmeters would trigger the flash.

- Leigh

mmerig · Apr 13, 2017

AgX said:
. . . . whereas my digital one (manufacturer re-checked) trips flashes.

A digital voltmeter that trips a flash unit would have an unusually low resistance for a digital meter, or any voltmeter for that matter. It's easy to make them with desirably high resistance, so I wonder if your meter is faulty. Using fixed-value resistors to see what would trip the Vivitar, it tripped at 22 ohms or less but not 33 ohms. Quite low compared to a meter.

Leigh B · Apr 13, 2017

mmerig said:
A digital voltmeter that trips a flash unit would have an unusually low resistance for a digital meter, or any voltmeter for that matter. It's easy to make them with desirably high resistance, so I wonder if your meter is faulty. Using fixed-value resistors to see what would trip the Vivitar, it tripped at 22 ohms or less but not 33 ohms. Quite low compared to a meter.

You failed to read my post immediately before yours.

The trigger sensitivity depends critically on the design of the flash.

- Leigh

PC-cord triggering of multiple flashes

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