Paul C. Buff, Inc. Technical Forum

My CST is connected to a PW FlexTT5 (Nikon version) using a hotshoe adapter cable. For readers who may not be familiar with the FlexTT5, it has two 3.5mm mono ports; one is to fire a flash, and the other to trigger a camera. The 3.5mm end of the adapter cable is plugged into the flash port on the FlexTT5, and the CST sits in the hotshoe adapter. Seems simple enough, but the CST is not responding to the FlexTT5's trigger. Same results when trying a CC. Tried a flash in the adapter, and it fires just fine. Any ideas as to why this won't work?

With the CST in the adapter and the adapter unplugged from the PW, can you jump the 1/8 plug to see if the flash fires? Also, is the plug a stereo or mono plug?

It's a mono plug, and jumping the end does cause the CST to fire.

It almost sounds like a polarity issue, though it will take some time to confirm or refute that.

1) I'm confused as to what actually causes the CST to fire. Can you briefly explain?

2) It seems unlikely that a polarity issue could occur when using a standard hotshoe adapter. Yes? No?

3) If I were to cut a cable and reverse the wires, could that potentially cause damage to the CST or the FlexTT5?

It is the closure of two contacts that fires any flash. Any further connections are for additional communication. A standard flash foot has a contact in the middle of the bottom, and one along the side rail. When that gets closed, it is just like when you press the test button. In your configuration, the PW is what actually closes the circuit.



Unlikely, yes, but certainly not impossible or unheard of.



No.

I need some help, because this isn't making any sense.

I placed a CST in a hotshoe adapter, then put a meter on the positive and negative pins of the mono adapter that would typically be connected to a trigger port. Sure enough, I see close to 3V DC. I replaced the CST with a flash, turned on the flash, and I see the same 3V DC. So, in theory, if a flash gets triggered, then one should fully expect a CST to fire. But, it doesn't. How can this be explained?

Can you set the meter for continuity? If so, check that the continuity of the 1/8 connection is matching with the center pin of the shoe. What adapter are you using?

The continuity (tested using an Ohm meter) shows that the center pin on the hotshoe foot is connected to the tip of the 3.5mm mono plug. The slide on the shoe also shows continuity to the other part of the mono plug. I don't remember where I got these adapters, but I'm guessing it was Flash Zebra. Here's a picture....pretty standard:

Is the CST "snug" in the adapter?

I had a problem once with a third party adapter: the fit seemed snug, but the center contact was just a bit far away (vertically) from the trigger/speedlight, so it wasn't making good contact. I'd hit the contacts (center and ground area on the adapter, ball-pin on the CST) with a pencil eraser or other contact cleaner, check to see the pin on the CST is "springy" and then try to eyeball it as you slide it in.

It is remotely possible (I had this happen once) that the fit of the third party adapter allowed the trigger to slide just a bit past the center contact, so it looks and feels fully seated, but is actually just missing the contact point (horizontally).

It doesn't seem likely to be a polarity issue to me. Possible, but not likely.