Vivitar 285HV Inconsistent Firing

[markd]

I have a used Vivitar 285HV that, for some reason, doesn't fire consistently. With the green/red alternating light (i.e. full charge) it may take 1 to 4 or 5 shutter releases (when on the camera or used with radio trigger). I've used this flash on my Elan 7n and even tried it out on my Rebel XT just to make sure it wasn't the camera.

The issue also manifests itself when firing the flash using the 'open flash button' (the red button on the foot). Usually the fourth or fifth press of the button will guarantee a firing but it's variable up until that point. I unscrewed the foot to see if there were any connections that seemed obviously wrong but everything seems alright. This particular unit doesn't exhibit any noticeable corrosion or damage. This happens using both normal AA's and rechargeable ones. I don't have an SB-4 adapter to test it with.

I tried reforming the capacitor (although I didn't think the cap was an issue as it fires off strong). No change.

Obviously this is an issue because I can't just waste 4 or 5 frames for every shot I'd like to take. Is there any way that I could diagnose a connection issue with the wires that lead to the foot? I haven't disassembled the rest of the flash just yet. Thanks

 

[benjiboy]

Mark I would strongly advise you NOT to dismantle any flash gun, because the charge that is retained in the capacitor even though the flash is discharged and has no batteries in it they are still capable of giving a fatal shock, take it to a repairer to check it out .

 

[John Koehrer]

Mark I would strongly advise you NOT to dismantle any flash gun, because the charge that is retained in the capacitor even though the flash is discharged and has no batteries in it they are still capable of giving a fatal shock, take it to a repairer to check it out .

Aw c'mon Benji, you just don't realize how quickly your reflexes work until they've been hit with 300+ volts. The 300V also melts scewdriver tips pretty neatly & creates nice white sparks.

Anyhow, it's probably corrosion or tarnish on the switch contacts. If you think it's a good idea to pursue cleaning them, DISCHARGE the main capacitor first.
I use a 100 Ohm resistor with insulated leads for it. The only thing exposed is about 1/16" at the tips.
Hold the resistor across the cap for about 10-20 seconds & you're good to go but if you reconnect the battery it recharges very quickly.

I have never heard of anyone being killed by a shoe mount flash since the current is so low. The old Ascor & Speedotrons could knock your ass across the room though & wouldn't doubt they could kill if conditions were right.

 

[Bob-D659]

The nice thing about the 285 is you don't have to get close to the main cap to clean the switch contacts in the foot. The bad thing is I doubt it is the problem. The pushbutton switch is first in line on the wiring to fire the flash. If both the camera and the button have problems firing the flash, the problem could be a poor connection or a partly broken wire from the board to the shoe. Another possibility is the circuit on the board that discharges a capacitor thru the trigger transformer, or the small capacitor itself.

when you split the case open, remove the alloy disc opposite the calculator, there is a screw hidden underneath it. The disc is stuck on with glue or double sided tape.

 

[markd]

Thanks everyone I'd read about the dangers of these caps so I'm trying very hard to avoid it. I actually don't seem to have a screw driver small enough to get the screws behind the calculator and the disc so I guess I'm going to be OK for now. I'm not going to hassle too much with it because I'm not really in the mood to electrocute myself. It works well enough shooting digital; I just have to make heavy use of the trash can button. Honestly, for the price I paid for this I think I'll just pick up another flash when I get the chance.

 

[benjiboy]

Aw c'mon Benji, you just don't realize how quickly your reflexes work until they've been hit with 300+ volts. The 300V also melts scewdriver tips pretty neatly & creates nice white sparks.

Anyhow, it's probably corrosion or tarnish on the switch contacts. If you think it's a good idea to pursue cleaning them, DISCHARGE the main capacitor first.
I use a 100 Ohm resistor with insulated leads for it. The only thing exposed is about 1/16" at the tips.
Hold the resistor across the cap for about 10-20 seconds & you're good to go but if you reconnect the battery it recharges very quickly.

I have never heard of anyone being killed by a shoe mount flash since the current is so low. The old Ascor & Speedotrons could knock your ass across the room though & wouldn't doubt they could kill if conditions were right.

I am completely ignorant about electrical matters , you seem to know what you're talking about John but the majority of the general public like myself don't, and would be safer to take the flashgun to somebody who does than to risk dismantling it and taking a risk of substantial electric shock.

 

[John Koehrer]

Can't deny it's not pleasant, I've done it a number of times & so far it's only caused this ttttttttttttwitch.
I try REAL hard not to have it happen again.
It's also safer while wearing your rubber undies.

 

[tkamiya]

Part of the flash circuit actually can have few thousand volt potential, although current is pretty low. Good thing is.... under most conditions, either the few hundred volts on the primary side or few thousand volts on the secondary side isn't fatal. Bad thing is.... under some conditions, it CAN be fatal. It doesn't have to be searing strong power to knock your heart out of rhythm. If someone is not fully aware of all the potential pit falls, it is best not to handle them.

This is not to say you cannot do it. Take pre-cautions and be reasonably educated to know what you are doing first - and at least, know what NOT to do first. I don't advocate "it's dangerous - don't do it" theory. I advocate "it's dangerous, approach with knowledge and caution" theory.

I had an unfortunate experience of touching about 500 volts of high current circuit. It was such a shocking experience, my whole arm was numb for the entire day and burned parts of my skin quite deep. Please don't rely on your muscle reflex to help you here. The current can travel fast enough to kill you long before you have a chance to react. In some circumstances, your muscle will be paralyzed or worse, contract in the wrong direction.

This is coming from someone who is a licensed electrician, and also a former electronics technician. (me)

 

[John Koehrer]

Again, uncomfortable not fatal. I've never seen more than a 350-360V cap in a SHOE mount flash. But that wasn't properly discharged.
I have seen at least one person "thrown" across a room while unplugging a head from a power supply studio flash.

 

[mhcfires]

I think the best idea is to have someone who KNOWS what he is doing fix it. I really don't think that we want to find out that you are on the other side of the flowers because you touched the wrong part. The last thing you want is a huge handful of volts, even at a low current it can kill you.

 

[olleorama]

volts aren't dangerous. amperes are.

 

[mhcfires]

volts aren't dangerous. amperes are.

True, but where there are volts, amperes are usually hiding out.