Ballast Problems

[GrapeApe]

I’ve been wanting to write about Ballast failure for some time now. The reason is all the people buying used equipment for their start up. Some people sell lights and don’t know they had a capacitor problem.
It’s also hard to spot a light that is running at 60%,if you have not been around a grow lights before. I did a C&P of Capacitor problems. I know others here have a lot of knowledge to share on rebuilds and trouble shoots. Please feel free to share your thoughts.

If the capacitor is enlarged, it has failed and needs replacement. Capacitors also can partially fail. Here, the fixture starts and runs continuously but comes up to only 10-60 percent of its maximum brightness. HPS fixtures with a partially failed capacitor have a lower light output, a lower power factor and reduced efficiency. This partial failure is not always visually apparent, and lights continue to function at reduced efficiency for extended periods of time.

[Uncle_Al]

Hi everyone OG original Overgrow member Uncle Al here, I am by trade an industrial electrician. I repair H.I.D. lights regularly, if I may I will share my tips for checking a H.I.D. ballast and capacitor. First off a safety warning, you can get killed if you try to work a live system, turn off the power, unplug the light cord from the wall.
Symptoms of a malfunctioning light are:

1. No start
2. Low output
3. Light that blinks on and off
4. Horrendous Stench
   A light that does not start could have any of these problems:
5. No power from source, look for a tripped circuit breaker or a blown fuse. If the power is ok look for a bad connection like a bad or corroded wire nuts. If the power checks out try a fresh bulb of the correct type and watts. If a fresh bulb does not solve it you are most likely looking at a bad capacitor, test capacitor. If the capacitor tests good and there is still no light the problem has been isolated to the transformer, the transformer may stink terrible if it smells bad it has cooked and let out the smoke. The only option then is to replace it. The transformer may not stink and still be bad by having an open circuit, this happens when the equipment has been mishandled for example carried by the wiring.
6. Low or diminished light output. There are only two options for this problem the first is a failing bulb, swap out to a fresh bulb, if that doesn’t get things bright the capacitor is failing. Test the capacitor.the capacitor may exhibit physical clues like being swollen or leaking electrolyte, those are bad for sure be careful handling leaky capacitors because some really old ones contain P.C.B. a cancer causing chemical. If the capacitor is not leaky or swollen test it electrically (don’t worry I’ll get to actual test procedure) if the capacitor reads less than the stated value it is weakened you will have to find another. Any electric supply house will have it.
7. A light that blinks on and off, the prime candidate for this is a bulb that has reached the end of it’s useful life, replace the light with another of the proper wattage. If it still blinks it is possible but less likely the capacitor is failing, test it electrically.
8. Horrendous Stench, if you smell the stink the transformer is failing or has failed, there is an internal short . The smoke is getting out. You cannot put the smoke back in . Take the light out of service immediately before it burns up . There is no possible repair other than replacement.
   Next post coming up: Checking a Capacitor Electrically.

[Uncle_Al]

Testing a Capacitor Electrically,
Before we get into it I must make the standard safety warning: You can get killed working on a live system. Always remember to remove the power from the system: turn off the power going to the device, unplug the light from the wall. Do not touch the capacitor’s terminals without discharging the capacitor first you could get a nasty shock that could set off a heart attack.

Things you will need to test a Capacitor:
1: A screwdriver, Phillips or flathead will work.
2: A test meter with a Capacitor symbol/scale
3: Optionally a soldering iron and solder.
4: A steady hand and the ability to follow directions

These are the tools of destruction.
First look at your Capacitor, determine the capacitance value according to the labels

This capacitor is for a 400w Metal Halide ballast, it says 24uf +/-3% that is the value we are looking for.
Now notice the terminals on top.

These are the connection points to the ballast also notice the presence of a resistor between the terminals, the purpose of the resistor is to self discharge the capacitor. Not all capacitors have this safety feature, that is where the screwdriver comes in. Touch the screwdriver to the terminals, both of them at the same time, it only takes a second to discharge. There may be a spark and an electrical snap noise. It is now safe to touch.

Shorting the terminals
Now take the meter and set it to the capacitance scale

pointing at Capacitor symbol
Now touch the meter leads to the terminals

the meter will show the capacitance value

This one is showing 24uf it is right on the money and we are good to go!
The meter you use could give a wierd reading if so you will have to unsolder one side of the resistor and recheck. If the reading is low or reads,. OL or O.O it is a bad capacitor it could read higher too but that is not that likely but as long as it is within the listed tolerance, in this case +/-3% it is still good

[Muleskinner]

great tutoriall!! I remember replacing the capacitors on my old ballasts, they get much brighter. SInce then I went to eletronic ballast and then LED. Magnetic ballasts are still the cheapest to operate, when an electronic ballast is dead, it’s dead.

It’s like today’s cars, when you open the hood and it looks like a giant computer.

[Uncle_Al]

It is just a part of my day job, I literally trip over these things. Thanks for the input.