HPS wont light up... MH runs fine. What's wrong HELP please

Guys I need help. I have a 400W switchable ballast and I'm in veg now and the MH bulb is working great... But I want to switch over to flowering this week and my 400W HPS bulb wont light up??? WTF is wrong? Took the bulb back to the store and tested it there... it works fine! I switched the socket (just cuz i had a spare one and i thought it might not be making the connection)... still nothing. I dont think it's the ignitor cuz the MH is working... This SUX!!! Please anyone have any suggestions? Help a brother out.

Thanks

This is going to be silly, and obvious - but are they the same wattage? And are you sure you have a conversion ballast? If not, the ignitor probably isnt good enough to get the HPS going [taking into account it worked at the shop]

ganjman said:

This is going to be silly, and obvious - but are they the same wattage? And are you sure you have a conversion ballast? If not, the ignitor probably isnt good enough to get the HPS going [taking into account it worked at the shop]

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Yeah they are the same wattage... and the ballast IS a conversion one. A question about the Ignitor... I dont know much about them, but would it be able to fire up the MH and not the hps. Wouldnt it be if it cant fire the HPS it wont fire the MH either?? I went and bought a new Ignitor yesterday but didnt put it in cuz the guy there said as long as the MH is lighting up its working properly... Please any other help?? need to get these girls in flower b4 they get too big.

Cheers.

Bab bulb a possibility? Is it new?

303 said:

Bab bulb a possibility? Is it new?

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yes brand new... took it back to the store & got it tested again... it works... its not the bulb..

I would make sure you lamp mogul (the socket it screws into) to be rated for HPS, some sockets wont make contact with the end of the lamp and the contact, I had to change mine out the other day.

I thought that as well... so I changed out the socket (mogul) last night... still nothing.. very aggravating... Anyone else?

OK so I did a thorough check on the wiring and it turns out that the wiring to the socket that the ballast is plugged into isnt grounded... (its an old house...only 2 wires L&N) I got some 3 core cable to replace it. DO any of you think that this might have been the cause for the MH to work and the HPS not to???

Cheers

It is possible, another thing to think about is if your ballast is pulse start or not and if your bulbs are the same... If you have a pulse start ballast, you must have pulse start bulbs.

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It's the ignitor!

The ignitor is only usefull for the HPS not the MH, that's actually one of the tests to check if the ignitor in a HPS setup is bad, put a MH bulb in, if it works the igniter is bad if it doesn't it's something else.

Good post andyboy, I was about to state the same thing. A hps bulb needs an ignitor, the mh doesn't.
If the ballast was sold as a switchable one, then either there's a switch on it, or you have to open it up and route the wiring through the ignitor. Most electronic ballasts will automatically switch the ignitor depending on what type of bulb is being used. If the wiring already goes through the ignitor then you need a new ignitor.
It says a lot for the caliber of people who work in hydro shops that they didn't tell you this.

Hairy Bob said:

Good post andyboy, I was about to state the same thing. A hps bulb needs an ignitor, the mh doesn't.
If the ballast was sold as a switchable one, then either there's a switch on it, or you have to open it up and route the wiring through the ignitor. Most electronic ballasts will automatically switch the ignitor depending on what type of bulb is being used. If the wiring already goes through the ignitor then you need a new ignitor.
It says a lot for the caliber of people who work in hydro shops that they didn't tell you this.

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Couldn't agree with that last line more Hairy Bob... I will drop in the ignitor when i get home and give it a shot. OK just so i get this clear... The Ballast I have has the wiring routed through the ignitor.. BUT the MH bulb does not need the ignitor to light it up whereas the HPS DOES need the ignitor... but is it ok to have the ballast wired up this way (thru the ignitor) permanently to run both MH and HPS? Thanks so much for the help...

If it's a digi ballast with switching capacity then it should be fine. Even if you have a normal magnetic ballast with an ignitor, it will run mh but because it's giving a kick of over 2500v to strike the arc (which it doesn't need) the bulb life would be reduced, although I don't know exactly to what degree or how quickly it would degrade, since I have never seen a test done on the long term effects of mismatching ballasts.

Yes its a magnetic Ballast... Tahnks so much for the info... didnt get to switch the ignitor lastnight... will try do it tonight and report back.

sounds like the ignitor is shot since the MH works but not the HPS. MH does not need an ignitor therefore it is working. You can get an ignitor at any electrical supply store and they are alot cheaper than buying a whole new ballast. Good Luck

im interested to know how this turns out because im going through the same thing with my 1000w

sohel001 said:

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an open ground will not cause a lamp to misfire. try bending the contact tab to make sure its making contact with the lamp base.

bewareofdogandowner said:

an open ground will not cause a lamp to misfire. try bending the contact tab to make sure its making contact with the lamp base.

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a ballast is basicly a transformer...transformers are generaly an ungrounded system because your taking your ground from the center tap of your transformer wich in turn is bonded to the system neutral at the utility connection on the primary side of you x-former...or in your case your picking up your ground through the wall socket your plugged into on the primary side ....your load side (to lamp) is getting its ground through the "common" connection on the ballast

EFF THIS!!! Ok so I changed the ignitor and its still not working!!! I really dont know!! ... Ok Im gonna open the ballast up and take a pic and post it on here to see if these people wired it right. I bought it from a local light store and it wasnt a pre-fab ballast. The store assembled it for me... (all they had were all in one units... light+ballast in one... got them to make a remote ballast.) Seeing as they said the total opposite to what you all are saying about the ignitor... its prob best to get your opinion on it.

Cheers... brb