Here is another fix for common Optical slaves to make them get along and play nicely with EX series speedlites.
It also offers a possible explanation as to why they don't play well to beging with.
Its posted with permission from a local Auction site:
This is not an auction but a helpful message for those who've bought a flash slave trigger (such as in auction 121454656) and found that it triggers their flash only once. The usual remedy is to turn the flash off and then on again, but this is a tedious answer to the problem.
You can modify the slave, as I have done, and have it work repetitively without any hassles.
Take the unit apart and find the two wires that go to the hotshoe into which the flash unit is plugged. Disconnect one of these wires (doesn't matter which one) from the hotshoe contact. Now connect a 150nF 250V capacitor between the end of the wire and the hotshoe contact from which you previously disconnected it. Also solder a 4.7MR resistor across the capacitor.
This is how it works: Normally the light from another flash unit triggers the slave unit, causing the SCR in it to turn on, which triggers the flash connected to the slave unit. The trigger current coming out of the flash unit can be high enough to keep the SCR turned on, resulting in it not firing repetitively. With the resistor and capacitor in series with the trigger circuit, the SCR will turn on and draw trigger current through the capacitor, thus triggering the flash unit. The trigger current will eventually charge the capacitor and then the current drops so low that it will cause the SCR to turn off again. When it turns off, the resistor across the capacitor will discharge the capacitor so that the unit is ready again to fire the flash, without the need to manually turn the flash unit off and on again.
This mod will cost less than $1 in parts, and take about 10 minutes.
Remember, this is not an auction. I'm just passing on a handy hint. I have made this mod to the unit I bought in auction 121454656 and it works well with my Canon 430EX speedlite and with a Sunpak auto 118. I expect it will work with almost any flash unit.
The only further advice I can give is that, depending on the flash unit, you may need to alter the value of the capacitor up or down slightly. (up, most likely) The voltage rating of 250V can be physically too large to fit, but you need this rating ONLY if the voltage across the trigger terminals of the flash unit is this high. If that voltage never exceeds 30V then you could get away with a 35V or 50V rated capacitor.
You can modify the slave, as I have done, and have it work repetitively without any hassles.
Take the unit apart and find the two wires that go to the hotshoe into which the flash unit is plugged. Disconnect one of these wires (doesn't matter which one) from the hotshoe contact. Now connect a 150nF 250V capacitor between the end of the wire and the hotshoe contact from which you previously disconnected it. Also solder a 4.7MR resistor across the capacitor.
This is how it works: Normally the light from another flash unit triggers the slave unit, causing the SCR in it to turn on, which triggers the flash connected to the slave unit. The trigger current coming out of the flash unit can be high enough to keep the SCR turned on, resulting in it not firing repetitively. With the resistor and capacitor in series with the trigger circuit, the SCR will turn on and draw trigger current through the capacitor, thus triggering the flash unit. The trigger current will eventually charge the capacitor and then the current drops so low that it will cause the SCR to turn off again. When it turns off, the resistor across the capacitor will discharge the capacitor so that the unit is ready again to fire the flash, without the need to manually turn the flash unit off and on again.
This mod will cost less than $1 in parts, and take about 10 minutes.
Remember, this is not an auction. I'm just passing on a handy hint. I have made this mod to the unit I bought in auction 121454656 and it works well with my Canon 430EX speedlite and with a Sunpak auto 118. I expect it will work with almost any flash unit.
The only further advice I can give is that, depending on the flash unit, you may need to alter the value of the capacitor up or down slightly. (up, most likely) The voltage rating of 250V can be physically too large to fit, but you need this rating ONLY if the voltage across the trigger terminals of the flash unit is this high. If that voltage never exceeds 30V then you could get away with a 35V or 50V rated capacitor.
From here: http://www.trademe.co.nz …Listing.aspx?id=123913060
Of course the link will stop working when the "auction" expires.
Hope it might be of use to someone, and prehaps someone with more technical know how than I can confirm it makes sense?
