MH light shutting off, HPS fine

I have had a 250w ballast with 250w MH and HPS light for two successful cycles. For this third cycle though, I noticed that my MH light was off when it should've been on. The MH light is turning on... and then turning off very shortly after, and the bulb will feel hot even though it's only been on for a few minutes at most. I (begrudgingly) switched to HPS light for seedling/early veg and it's running just fine, even for for 20-22 hours per day. I ordered a new MH light, and when I put it in... it did the exact same thing as the last MH light did, turning on briefly then shutting off. So I am led to believe it might be an issue with the ballast? Curious why it would only be doing it with the MH lights though and not affect the HPS light seemingly at all? I wouldn't even really know where to begin on troubleshooting a ballast for this kind of issue.

Bad bulb, goes into autoshutdown so it doesn't explode. MH's will explode if they get forced to run when they shouldn't be.

(Thought came to me.... Are you running a MH capable ballast? If not you may need a conversion bulb.)

GanjaJack said:

Bad bulb, goes into autoshutdown so it doesn't explode. MH's will explode if they get forced to run when they shouldn't be.

(Thought came to me.... Are you running a MH capable ballast? If not you may need a conversion bulb.)

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I guess it's possible the new bulb they just sent me was already bad. It's just weird that it's both the MH's lol. And yes my ballast is MH compatible. I've run it for two grows now without any problems. The first bulb ran first two fine, now its not working. And the brand new one doing exact same thing.

Antman603 said:

I guess it's possible the new bulb they just sent me was already bad. It's just weird that it's both the MH's lol. And yes my ballast is MH compatible. I've run it for two grows now without any problems. The first bulb ran first two fine, now its not working. And the brand new one doing exact same thing.

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So now it's basically guessing whether it's the bulb or the ballast...

Is it a digital ballast?

Yes it is electronic/digital ballast. Yescom 250w MH/HPS ballast.

Technically, you don't really need the MH for early veg as you know.

Personally, I like to give them a nice tight blue light in the beginning too... You could always get a 2 x 2 or 3x3 T-5 flourescent fixture for veg. Replacing those bulbs one at a time isn't as much of a problem, knowing if its the fixture or the ballast or the bulb, etc etc.. far easier to trouble shoot and are a bit more reliable.

I use that myself and it grows plants to 2 foot easy, after that it gets a bit "iffy". (I've actually considered experimenting with flowering under it just for funs to see what would come out.

But, yeh the T5's will grow the plants nice and thick in veg.

I used to get this problem a lot when running MH bulbs that can run on HPS ballasts, I think they were called conversion bulbs? So I switched to regular MH bulbs and same thing happened, so got new ballasts of a different brand and they worked fine. A bit of swapping between new ballasts and new bulbs of different kinds and I worked out that sometimes it seems there is a compatibility issue between bulbs and ballasts depending on brand.

Yeaa I know I don't 'need' it. I'm kinda comin off a high with my second harvest being much better than my first, was hopin to keep that up but this kinda put a hamper on that lol.

I was curious if having one work and the other not work was a common problem. But if not, it might just be a coincidence and both the MH bulbs are bad. At least MH is the cheap one lol. And yea I have heard about that, I bet those fluorescents are a lot easier to find too.

GanjaJack said:

Technically, you don't really need the MH for early veg as you know.

Personally, I like to give them a nice tight blue light in the beginning too... You could always get a 2 x 2 or 3x3 T-5 flourescent fixture for veg. Replacing those bulbs one at a time isn't as much of a problem, knowing if its the fixture or the ballast or the bulb, etc etc.. far easier to trouble shoot and are a bit more reliable.

I use that myself and it grows plants to 2 foot easy, after that it gets a bit "iffy". (I've actually considered experimenting with flowering under it just for funs to see what would come out.

But, yeh the T5's will grow the plants nice and thick in veg.

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I've seen some t5 buds that were nice! back in the day.

MedicinalMyA$$ said:

I used to get this problem a lot when running MH bulbs that can run on HPS ballasts, I think they were called conversion bulbs? So I switched to regular MH bulbs and same thing happened, so got new ballasts of a different brand and they worked fine. A bit of swapping between new ballasts and new bulbs of different kinds and I worked out that sometimes it seems there is a compatibility issue between bulbs and ballasts depending on brand.

Click to expand...

Interesting. Well since MH bulbs are relatively cheap, I might just try a couple out. Because the ballast seems to work fine with my HPS.

Antman603 said:

Interesting. Well since MH bulbs are relatively cheap, I might just try a couple out. Because the ballast seems to work fine with my HPS.

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I know that a lot of MH bulbs won't run on digital ballasts. They need old-school magnetic ballast. At least Hortilux Blue MH bulbs were like that.

So, I just went and got another MH bulb. I don't wanna jinx it, but it has been on for about 3 hours now. It's possible this was just a strange coincidence of my first MH bulb going out, and then purchasing another bad MH bulb right after... leading me to an incorrect diagnosis. You guys helped clear up that this type of problem would most often be a compatibility issue in design. Seems unlikely that a MH/HPS compatible ballast would just all of a sudden lose compatibility with one or the other, as was my original thought.

I have a feeling this 3rd bulb solved it. Fingers crossed. I appreciate the assistance everyone, thanks.