Camera flash repair

Howdy all,

I just received an old camera flash in the post and on opening the battery compartment i was met with two very corroded AA batteries. I was wondering if the corrosion will have caused damage to the flash beyond repair or if cleaning the contacts and replacing any corroded wire will do the trick. I was also wondering if there is anything to be cautious of in the circuit e.g. the capacitors.

Thanks, Wiz

It will probably still work if you clean it up. Thankfully that looks like alkaline batteries leaked, the damage isn't as bad as zinc chloride ones would cause.

Yes - do beware of high voltages. The blue capacitor will typically charge to around 300V !

Brian.

I cleaned everything up, and now i'm getting the whine as the flash charges but it's week and intermittent and sometimes requires i shake the entire flash. There is also no light indicating power. I've included two photos of the circuit board which appear most damaged. A switch and resistor. I was thinking of replacing the resistor and removing the switch to clean and then replace it.

Edit: The flash fires with the open flash button. The red light does not glow when the flash is ready for firing

The whine indicates the charging circuit is working. The weak flash means it isn't reaching full voltage.
I would suggest cleaning the whole board with a proprietary PCB cleaner or if you don't have any, use isopropyl alcohol and a brush to work it into the hard to reach spaces. I have an old tooth brush in my toolbox for exactly this situation. You should find the flux residue on the board dissolves completely. Then place it somewhere warm but not near a naked flame for 24 hours and test it again.

I'm suspecting the problem is the board itself has absorbed moisture and has become slightly conductive. Although the voltage is high, the charging circuit doesn't produce much power, that's why it takes so long to fully charge the big capacitor. Anything, including leakage through the board itself will consume some of that power. That kind of board is made of a mixture of paper and resin which can slowly become damp, if cleaned to expose all its surface area then kept warm, it will dry out and hopefully start to work properly again.

Brian.

Wow, talk about cheap and nasty. Most definitely manufactured in China.
Never seen a transistor TAB being cut off so it fits in the case.
You should wash the whole PCB in hot soapy water, rinse thoroughly and
dry it completely. That will ensure to remove all the acid.
Spray some contact cleaner into any switches. Take note of all the trim pots
settings, then spray them as well. Using a screwdriver rotate them several times
clock-wise and anti-clockwise, then moving them back to their original positions.
Regards,
Relayer

Also examine this copper trace where there might be a break. The green film peeled away. It's overlapped by pale blue corrosion.

BradtheRad said:

Also examine this copper trace where there might be a break. The green film peeled away. It's overlapped by pale blue corrosion.

View attachment 166448

Click to expand...

What would I looking for here, and if i found whatever it is what could i do to fix it. Worth noting that another one of these flashes is about £13 I'm mainly repairing it on principle and to learn.

The board substrate is (or should be) an insulator. The copper tracks on its surface are conductive and link the components together. They are the equivalent of wires but constructed as copper strips bonded to the board. What Brad is saying is the battery chemicals may have 'eaten' the copper away resulting in a break in the connection. If you clean it up you might see a break in the copper. If there is one, follow the copper to the nearest solder joint in each direction and bridge it by soldering a length of normal insulated wire across it to restore connectivity.

Brian.

I agree with Brian's post, preceding.

To clean away blue crust, I often use baking soda solution (sodium bicarbonate). It generates frothy carbon dioxide foam due to the chemical reaction between acid and base.

It's important that we remove all chemical residue. Whether its pH is acid or salt or base, it may be able (of itself or from reacting with water or other material) to conduct electricity to some extent. Or it can eat away copper traces.

After cleaning the board, use a magnifying glass to examine for breaks in the traces.

I have bought some isopropyl alcohol and will get back to you with results! Thanks for everything so far.

Hi,

Electronics usually isn't sensitive with the cleaning process.
In the 1990s we cleaned PCBs after wave soldering in a bath of alcohol, surely there was water, too.
Later we used non alcoholic cleaning.
Later came the "no clean" flux. No need for washing standard PCBs, but some PCBs needed washing.
This was and is done in water containing alcalic solution containing tensides...and after this with demineralized water.
Most electronic parts won't be harmed.
Some parts don't like washing:
* uncoated film capacitors (where water may come inside)
* contacts, connectors, unsealed relays ... with gaps where water come inside but rather difficult out (it maybe needs drying with vacuum and/or high temperature)
* ultrasonic cleaning of XTALs (may break caused by resonance) and (sealed or not) contacts (may stick together by "ultrasonic welding")
* other components

I've heard that some do PCB cleaning in a standard dish washer. I've never done this. But there are professional PCB cleaning machines that come from houshold machines brand and look very similar ;-).
Not knowing about temperatures, timing, materials, cleanser...


Klaus

I brushed the pcb with isopropyl alcohol but alas, i'm getting an ever weaker whine now and much more intermittent. I seem to be damaging it more every time i open up the case and noticed sires breaking that are too small for me to resolder. Is there anything worth salvaging from the remains?