YerkWorks 4:49pm, 18 November 2009
After understanding how the RP JRx systems work and making the RPcube for the Nikon flashes ( I decided to explore this on the Vivitar 285hv. The thyrister is essentially a resistor to reduce the signal voltage telling the flash to reduce all or part of the voltage stored in the capacitor. It seemed to me that if you can reduce the flash output through a switch you should be able to do the same through the JRx controls.

It works, you can get 1/1, 1/2, 1/4, and 1/16 through about half the dial range on the JRx transmitter. These were tested by comparing the thyrister switch settings and the JRx dial settings through the histogram on my camera (these were spot on, more so than the same "test" performed with DIY RPcube I did on my sb-600). Any setting below that appears to give something that looks like 1/64 or less compared with the output of my sb-600.

RPCube for Vivitar


I haven't had the time to do a hard wiring yet but I figured I would supply the information if anyone else wishes to give it a go and post their results. to date, I have just made the connections by taping the appropriate wires in place. This is what needs to happen to make it work:

1) If you take apart the thyrister you will see that pins 4 & 5 are shorted together, so your setup will need to connect pins 4 & 5 together. The flash will not fire remotely without these pins connected, but it will test fire which threw me off until I took apart the thyrister.

2) The quench from the 3mm stereo cable needs to be connected to pin 2.

3) Ground and the trigger can be accessed through the hot shoe or the vivitar cable remote connector in the side.

4) Figure out how you want to make it all look presentable and your done.

NOTE!!!!! While researching to find the pinouts for the thyrister I found a blog stating that pin 1 is HIGH VOLTAGE and was tested by an unlucky gent. I took his word for it and didn't test it.

Note: Pin 4 is not used and is not connected to anything in the thyrister. Pin 3 is the low voltage signal that would have fed into pin 2 after going through the thyrister and being reduced to the appropriate level (which you are now supplying to pin 2 through the JRx).

I take not responsibility for the accuracy of this information, or any harm that may come to equipment or person if you attempt. Proceed at your own risk. And stay away from pin 1 or the capacitor if you decide to take apart the flash, unless of course you like visits to the hospital or possibly desire to test out the whole afterlife thing.

Also as a side note, I notice that using the dials on the RP Rx cranks out full power on the flash regardless of where it is set when first turned on. You need to actually turn the dials after you turn on the transmitter and all receivers to send the dial settings.
Eng-Shien 8 years ago
Nice work. There are a whole lot of other TTL flashes from the film-era that should be able to be power-controlled by the JrX receivers.
aperryproductions 8 years ago
I'm sorry, but I'm just trying to clarify and be a little more blunt.
So you're saying:

a)remove the front dial piece
b)short 5 and 6 together
c)add quench wire to 2
d) add trigger and ground to normal spot on the foot
DavidMHall 8 years ago
Eng-Shien wrote
Nice work. There are a whole lot of other TTL flashes from the film-era that should be able to be power-controlled by the JrX receivers.

It isn't a TTL flash. That's the bloody beautiful point.
Eng-Shien 8 years ago
DavidMHall I see. So even Thyristor flashes have squelch (if you can find it). Neato.
Idaho Fossils 8 years ago
Hmm, If this works...I could sell my 3 SB-600s for ~$500ish...Buy three thyristor based flashes for ~$20-$30 each, and spend the difference on an AB800+Vagabond. Tempting. This deserves some more looking into.
aperryproductions 8 years ago
terrific it works great. I put a stereo jack right in the casing. Because the quench and sync signals are already connected to where the thyristor would go all I had to do was run a ground wire up from the board. Then connected the quench cable to your pin 2, shorted your pins 5 and 6 on the inside with an extra lead connected to the sync on the jack, and the wires barely had to travel. Thanks...This just made my 285HV 10 times more valuable.
aperryproductions 8 years ago
Leave the front module off after completing. It shouldn't matter if plugged back in when not plugged into your jrx, but getting the quench signal from more than one place can't be good.
strobe right 8 years ago
Has anyone tried this with the older 283s? I have 4 of the older 283s with high trigger voltage ( 265 volts ). Would it be safe to connect them to a jrx in this way?
Spectrum Visuals 8 years ago
i'll like to know about 283s also
abbemu Posted 8 years ago. Edited by abbemu (member) 8 years ago
for 283.. check this out.., and yes.., 283 is quench-able

If you interested to make your own (DIY) Radiopopper JRX, check this one out.. ;-)
esqphoto Posted 8 years ago. Edited by esqphoto (member) 8 years ago
i completed this mod (hard wired) in preparation for radiopoppers. tested it with ebay triggers, which have mono (not stereo) plugs, and all i get are tiny pops of light. any idea why this is? does this mean it will work properly with radiopoppers?

edit: i forgot to mention, my hardwire mod is a female stereo jack on the flash body.

Follow up: got some help from a discussion topic I started. Looks like the mono cable is grounding the trigger and quench terminal within the stereo socket.

should still work with RPs (hopefully).
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