[Closed] Project: Neon Based Capacitor Leakage Tester Utilising a Camera

I did that with one of those early 1980s disk cameras to get the up converter for my seedling protector.
I have another PCB from one of those. They are better quality than that one too.

Yes, many people might have an old camera they can scrap. In such case they don't need to buy the reduced price Kodak (which is cheaper than the parts!)

I did a capacitor only tester earlier from a scrap camera. I'll be explaining how to wire one not just for capacitor testing but other tests. You can use one of your scrap camera boards instead.

Great idea,though I recall seeing this same idea over there. Just looked cant find it. Great minds think alike,A

Edit;ask at photo processing shops,they take the film out and bin the casing and components.

Great idea,though I recall seeing this same idea over there.

Yes I recall that thread too, but I believe Michael's version is a more elegant solution if you don't already have a scrap camera board available.

Just looked cant find it.

No doubt deleted due to lack of "meaningful content" or some other equally absurd reason.

Regards

I have nice pics and the main board running as 260V PSU with less scary 1uF instead of 300uF. I've been busy setting up a Linux server and migrating 300G files from a dying Win2K server.

Well, later I will do the deluxe version with diode / Transistor testing. But this is the most important test gear after a DMM for non-electrolytic capacitors in valve radios. Waxys, brown hunts and black hunts and TCC "xxxxmites"...

The basic idea is to use a flash charger (300V in modern cameras and up to 600 V in old ones).

The changes:

• Remove flash tube!
• Remove high voltage Electrolytic (often 300uF 400V) and fit 500V to 1000V foil capacitor of 270nF to 1uF.
• Add 2 x 1 M ohm resistors in series between capacitor + (though the foil replacement isn't polarised) and Plus test terminal.
• Add a neon with 100V ceramic 100nF across it, in series between capacitor - and Negative test terminal
• Add on off switch to battery
• Either short out or fit button on original "flash" enable button

If you have no suitable old camera, then buy a recyclable Fuji or Kodak in Tesco (Can be as low as £4 / €5 and certainly under £8 / €10).

Peel off the labels and it will pop apart.

Remove The Battery! 

Identify the flash charging PCB.

Make sure the capacitor is discharged! Short out the pins with a screwdriver!

Change the Dangerously high value Electrolytic for the 270nF to 1uF higher voltage rated foil type. Also remove the flash tube.

Have a suitable case with two terminals, power switch, hole for neon. The only additional parts needed are the neon, 2 x 1 M Ohm resistors to feed from +300V to + Terminal (so it's safe, but see warning!), and a 100nF 100V rated ceramic or foil capacitor across the neon.

You probably want a slightly bigger case. I had to clip off the edge of the PCB. I used a piece of marge tub plastic as an insulator under the PCB. I also used a spring loaded switch so it can't be left on.

Wire a battery holder to the power switch.

Assembled and working ...

Theory:

The neon and capacitor with the 2M resistor will form a relaxation oscillator, the frequency depends on supply voltage. With a short on the terminals the Neon will almost be steady with a 300V supply and look solid (50Hz to 100Hz?) with a 600V supply. With a 10 M ohm resistor the neon flashes are almost slow enough to count. With 100M Ohms the flashes are once every few seconds.

With a really good vintage paper cap, or mica or ceramic, the neon may only flash once. At once a second or faster the leakage is often too high. Typical waxys or brown hunts will look like a short!

WARNING! Danger Will Robinson!

The leakage tester on its own is safe even with a 600V source the 2 x 1 M ohm (to avoid break down/ leakage!) is safe.

But if you charge a larger external capacitor, there is then enough current to kill you. Most Electrolytics are too high leakage for this, but don't risk it!

Interestingly all my 50V ceramic capacitor "pass" (look like open circuit) even with my 600V tester!

That has reminded me that i have a PCB from an old Kodac disc camera waiting to be made into a cap tester. They had two AA cells.

Brought to my attention by another member: To address yet further 'Fake News' from elsewhere, this Vrat thread is not long gone.