Hps flicker...bad ballast?

Hello everyone I’m new to the forum and new to growing. I’m currently gathering all the necessary items to begin my first grow and I’ve run into a issue with my light . It’s a C.A.P. Light with a Quantum II 400 watt hps ballast. I purchased the light used and it came with 2 optilux 400 bulbs (one new, one used). My issue is after the bulb lights about 5 mins into operation it starts to pulse/ flicker ever so slightly once or twice a minute. the light never goes out or even comes close, but I don’t believe it should be doing this. I’ve swapped out both bulbs and they both do it. Any ideas?

Just as you said, bad ballast, might I recommend LED next time. @Watt-Sun


The light and ballast cost me 25$ so not a big loss Eventually I would like to try the led route after I get a little practice. Thanks for the input.


@Watt-Sun i know a guy an his hps takes 15 min to warm up.it flickers an dimms a little on an off during this stage,after 15 mins is fine :slight_smile:


I will have to give that a try. I haven’t let it run for very long maybe 8 or 9 minutes just to try it out.

There was a definite improvement the longer I left the light on. It went from several “flickers” per minute to maybe once every 10 min. I watched closer this time and the “flicker” appeares to be the light getting brighter then returning back to normal.

You’ll want to make sure that if you turn the bulb on, and then off, that you let it cool for about 10-15 min before turning it on again.


@Watt-Sun don’t forget to wear your sunnies,:slight_smile:


Definitely sounds like a bad ballest which is why you got it so cheap would be my guess
Check out lec lights as well they are more efficient that hps
Since toull need to but a new one


Not discounting the effectiveness of cmh at all, but did you happen to look at the spectral distribution graph they put up for led? All of these light manufacturers regardless of the type are a little guilty of not telling the whole truth.

On a separate note, I seen a pretty wild fixture over the weekend. Two 315 cmh bulbs with a spot for you to add hps bulb and ballast in the middle. It definitely wasn’t cheap, but I’m betting you could do some pretty wild stuff with it!


I definitely will be interested in upgrading eventually but for now until I know whether or not I’m able to be successful growing I’m hoping to keep it as cheap as possible with second hand stuff . So far I’ve been able to get 2 hydro farm inline fans, 4” carbon scrubber, ph meter, light fixture (and broken ballast apparently lol) 2 bulbs, a cabinet, pots, ducting, ratchet light hangers, and Mylar for just about 100$. A Lot of people have given up growing around here now that the have legalized recreational use and sale so I’m trying to take advantage of the deals so craigslist is my new best friend lol


That qualifies as a faulty ballast and is very hard on bulbs an HPS or MH should arc then start and warm steady until fully lit about 2-5 minutes if it turns off at any point during this and comes right back on seconds later bulb life is lost. In case of an MH they can actually pop explode. If it flickers and is extremely hard to start it is capacitor not building enough voltage to arc if it starts fine and shuts down once hot it’s the ballast HPS has a capacitor and ballast MH has ignitor capacitor and ballast
Each component is inside a ballast case :wink: and entire unit gets name ballast when really it is broken down into cheap and easily replaced parts. Digital ballasts are not repair friendly but the magnetic ones are easy to fix


The light never shuts down. The flicker I’m seeing is actually the bulb getting brighter for a split second then returning to normal. Thanks for the input, I’m bringing the ballast and bulb to my local hydro store today to trouble shoot it with another bulb/ ballast

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Went to my local hydro store and the were nice enough to run my ballast and bulbs with their equipment. As many of you had guessed, the ballast is failing. Time to start shopping.


@Donaldj copy,10/4 thought might of been the same things me ol mate thought :slight_smile: good call aswell