Testing an old flash for voltage

[KeithB]

I am in need of a flash unit, but don't want to spend the money at the moment for a new one.

My XS manual warns about using "high voltage flash units".  Is there a way to test my 30 year old flash to see if it is "high voltage" or not?  Just what is high voltage?  above 5 V? above 12? above 50?

[Bob Atkins]

As far as Canon is concened for older SLRs and DSLRs "high voltage" is over 6v, though it's said by some that under 12v is just fine.

True high voltage flashes tend to have a sync voltage between 200v and 400v. That's high and you wouldn't want to use one except on newer bodies and even then the voltage shouln't exceed 250v.

If you have a voltmeter, just measure the voltage between the flash contacts when it's charged. Uusually one terminal is on the bottom of the flash shoe and one is on the side. If it's 200v+ it can give you quite a nasry electric shock if you touch them, so make sure you're using an insulated probe and keep your fingers away from any exposed metal parts.

My guess is that most old, third party flash units will probably be high voltage.

[klindup]

I endorse what Bob says having had a lucky escape.  I have a Mecablitz hammerhead gun that I use regularly with a Rolleiflex.  When I bought my 40D I wanted to try it with my flashgun.  Fortunately I had mislaid the connecting lead and in searching the web for a replacement discovered that the trigger voltage was 300 volts.  If your flashgun is from one of the major manufacturers you may find information on the  trigger voltage on their website.  An e-mail to Metz  gave me the answer about the voltage used on my gun.

Ken Lindup

[KeithB]

I measured my flash and found it to be 34 V - high enough that I did not want to risk it.

I ordered a self-synd adapter for about $50, but then had second thoughts.  Using a manual flash (designed for lenses that could easily hit f/2) seemed to be a big step backward - especially when my "free" flash ended up costing $50. 

Therefore, I am going to return the safe-sync adapter and get a 270EX.  It will give me the more reach that I need and allow for much more control over the flash.  And - not incidentally - be easy for my wife to use if necessary.

[nikonian]

Nowadays things seem to be getting better. Many of the new camera designs say that the voltage to the sync socket can be high. THIS DOES NOT INCLUDE THE HOTSHOE. Some say up to 400 volts. Canon say up to 250 volts. Fuji 400 volts. 400 volts, now that rings a bell, SCR`s are usually 400 volts max. When you check the voltage use a digital meter as moving coil meters usually discharge the storage capacitor.

[Bob Atkins]

Canon's specification of 250v on the newer DLSRs applies both to the PC socket AND the hotshoe. I'm not sure about other camera makes. If in doubt, assume the sync voltage is low and use a Wein "safe sync" adapter.

[nikonian]

Canon's specification of 250v on the newer DLSRs applies both to the PC socket AND the hotshoe. I'm not sure about other camera makes. If in doubt, assume the sync voltage is low and use a Wein "safe sync" adapter.

Please read page 102 of the Canon 5D manual, paragraph 3.  > 250 volts on sync socket  and no high voltage on the hotshoe. Regarding safe sync`s, an excellent battery less design is to be found on Sam`s strobes. I have made several other designs but all requiring a battery.

[nikonian]

OOPS sorry, that should read < less than 250v. 

[Bob Atkins]

Well, this is from a 2007 article by Chuck Westfall, Canon USA's chief "guru" on all things technical and especially on the Canon flash system (where he literally "wrote the book" - The Canon Speedlite Reference Guide- on the subject!).

The trigger circuit voltage (TCV) rating for any EOS SLR is the same on the hot shoe as it is on the PC terminal (if the camera has one), but the acceptable TCV level varies according to the camera model. Incidentally, the main reason for the difference is the way the X-sync signal is generated. With the 250V cameras, the X-sync signal is generated electronically. With the 6V cameras, the X-sync signal is generated mechanically. There are no guarantees, but going forward I anticipate that most if not all future EOS SLRs will be safe for TCV up to 250 volts.

Canon Digital SLRs safe for TCV up to 250 volts:
EOS-1D Mark II N, EOS-1D Mark II, EOS-1Ds Mark II, EOS-1D, EOS-1Ds
EOS 30D, 20D, 5D
EOS Digital Rebel XTi, XT (400D/350D)
EOS D6000/D2000, Kodak DCS560/DCS520 (circa 1998)
EOS-DCS series (circa 1995)

Canon Digital SLRs safe for TCV up to 6 volts:
EOS 10D, D60, D30
EOS Digital Rebel (300D)

What the 5D manual says is not at attach "a high voltage flash" to the hotshoe as "it might not work". It doesn't specifically say it might damage the camera - but on the other hand it doesn't say it won't. It also doesn't really define "high voltage", though in the previous section it mentions 250v on the PC connector. There are certainly hotshoe flashes with a TCV over 250v.

Since there is clearly some conflicting information here, this is a case when "if you aren't 100% sure, use a safe-sync" applies.

It does make sense that the PC and hotshoe TCVs should be the same, since it's unlikely that Canon used two different methods of flash triggering (electronic and mechanical) in one body.

[nikonian]

Hi Bob , it must be that the centre pin on the hotshoe is OK for high voltage, but its a bit to near the logic pins for safety. I have experimented with this and it`s impossible to short any pin to the centre pin. Another thing that puzzles me is , on UK forums the most common subject is radio control of flash and firing of camera, but on your forum I haven`t seen a mention of it yet. Is there any reason for this ? I made up a gizmo that optically and audio fires a flashgun on the second flash of a master flashgun. But this now seems to be redundant.  Ah well.