Repalcing the hot shoe foot on flash

Hi all
I done a bad thing!
I dropped my K7 but fortunately the only damage was the foot on the metz 48f.
The nice people at Metz are estimating the repair to be around £70.00
while the parts are 12.00. I am an engineer but they have even frightened me with tales of high voltage and the need for specialised repair.
I have looked on the world wide wobble thingy and have seen a great picture by picture replacement of a foot on a Cannon.It really does not look that hard
I am going to attempt the repair - so 2 things
1. Has anyone replaced a foot on a Metz or any other Flash
2. Would anyone like me to log the repair as I do it

Mike,

Commiserations - are you sure there was no damage to the camera (esp. to the hotshoe area)?

BTW - well done on your weekly comp entry

I've taken flasguns apart and you have to be incredibly careful that you dont get a nasty shock, there always seems to some residual charge in the capacitors. The belt from the tiny flash in an Optio was worse, much worse, than 240V AC.

Ken,

You might have been one of the kids like me - putting metal eating utensils into powerpoints when we were very (very) little, getting bowled over backwards, and then trying it again to find out what the hell just happened there?

I've had some nasty belts from the little caps in pocket digicams. They're a real pain in the fingers Goodness knows what kind of shock you'd get from the Metz - the energy discharge could be seriously painful or fatal (esp. if you have a heart condition). Obviously manufacturers have to cover themselves.

Somewhere there was a nice guide to correctly discharging flash caps... wish I could find it. Definitely do NOT just short them out!!!

Some flashguns (like the AF540 & AF360) have feet that can be removed and exchanged without having to disassemble the body. The AF540 even has a connector - so it's just 4 screws and unplug! The AF360 has to be desoldered - but that's not hard

Matt

No, but similar. We had a table lamp the cable of which my father had extended with one of those in-line pug and socket arrangements. I suspect he had installed them the wrong way round so when pulling them apart you could get a quite delightful belt. It seems astonishing now that there was fun in this.

DC shocks are generally worse than AC shocks in as much as AC shocks make you shake but DC makes you grip.

We use 300 and 600 Volts DC power at work and although no-one has tried it, both are generally considered to be immediately lethal.

Certainly, leave the unit unpowered for a couple of hours before starting - that'll lower the stored charge for a start.

On the 'net, some suggest discharging with about a 10k resistor. Make sure you insulate the resistor legs so you don't short on anything else (you can stuff the capacitor with a quick discharge ). I seem to remember one guide would discharge with a high value resistor first (e.g. 1M), then proceed to the lower value to bring the charge right down.

Some insulated wire (or shrouded tip meter probes) going to a multimeter and the resistor should do the trick - then at least you can see the discharge proceed as well

Obviously - caution and a steady hand are both required
(Usual disclaimers apply here - £70 isn't much compared to your life )

Matt

If the flash is designed correctly and the capacitors correctly specified then a rapid discharge should not damage them.

A good safe design will have a bleed resistor - maybe around 1MOhm across the HV capacitors which will be at around 400V (maybe more). In operation a good quality Xenon tube, once the trigger voltage has been applied to the third terminal, will have a very very low impedance and the discharge could take as little as 1ms although for photographic use and management of the flash time it may be longer.

When taking it apart, the OP should leave it without batteries and discharged for several hours. Even then, capacitors have a wonderful ability to "recover" and could have 100 or 200 V across them. Discharge them using a 10kohm resistor - and leave it fixed in place while working. There may also be a second capacitor - maybe at a lower voltage (around 250 to 300 V ) which is used to provide the energy for the trigger pulse which is up in the 6 to 10 kV range.

Having spent time designing high power flash circuits - with a visible range of 8 miles, I know the possible dangers and working of them.

JUST BE VERY CAREFUL - if you are then repairing the mechanical side will be easy, just do not play with the electronics.

We use 2-3 mains lightbulbs connected in series to discharge our capacitors (substantially larger than you would find in a flashgun).

What we will use when you can no longer get incandescents is another matter.

AC can also grip. I nearly killed myself when experimenting at the age of nine or so. Fortunately I pulled the plug out of the wall before it was too late. Still have the scars on my hand today.

G

Industrial incandescents have not been banned - just domestic. You may need to go down to 120v versions though - in the longer term.

I thought the ban was for 100W incadescents only, and that lower ratings would still be available...

Lower wattage ones will follow - 150W went first then 100W and soon to be followed by 75W and 60W.

The lower wattage will probably disappear as full size lamp but remain in the small and miniature sizes.