tattoo machine help

can somebody help me out here, the problem is, i have a tattoo machine, based on two coils which create an electro magnetic circuit, which pushes an armature bar up and down, which then drives the needle bar etc.

when i power up the machine, its is running well for around 30 seconds, and then is gradually dying down, and eventually stopping.

is it a problem with the coils do you think? or maybe the capacitor?

any and all help is appreciated.

Well capacitors are pretty cheap, considering. Could you replace the capacitor and see if that works?

How old is the tatoo gun? Are there signs of overheating?

it is a few years old, picked up second hand, but it's a problem i have never come across before, and no signs of overheating. some people suggested the back spring might be at fault, or the contacts dirty, but that definitley isn't the problem. replacing the capacitor seems like the next step then?

What type of power supply?

Sounds like something is getting hot, even if it's not immediately apparent.

dc power supply up to 12 volts.

Now this is just figuring here, but maybe the capacitor went bad, or is going bad, thus it isn't capable of capacitating at the required amount....which would support the slow fade until the device will not vibrate.

If the capacitor is electrolytic, I wouldn't be surprised to find that the capacitor is just too old, and the dielectric has crystallized (which again, supports the slow fade out. Some capacitance VS Nominal capacitance)

I guess there are three ways to troubleshoot the capacitor.
1. Replace with a new one and see if the machine works better.
2. Take the capacitor out and check the capacitor with a capacitance meter.
3. Measure the voltage and amperage across the capacitor when the machine is running. If a slow drop occurs coinciding with the machine slowly fading , then the best bet is that the capacitor is bad.

Also, if the capacitor went bad, see if you can find out why. Is there too much heat next to the capacitor? If so, why is there too much heat? Is one of the power supply IC's not properly heat sinked etc etc.