problem with a 400W mh setup

Hello, I am having a problem with my light setup. It's a 400W Phillips MH put inside a cool tube connected to an extractor outside the box. While I was trying to lower the light down it turned off. After I turned it back on, it wouldn't light completely, it just remained in the startup phase, emitting a low light and looking like it's about to start anytime soon... but nothing happened. On top of this, the ballast was making a loud buzzing noise, something it hasn't in the past.
I quickly found out that the connections to the light were somewhat "loose". Redid the connection on the whole instalation, including balast and AC. It didn't solve anything.
Then I noticed that if I moved the light's cable around a bit, the light went fully ON. Bought a new thick cable, I don't think I can possibly find one of better quallity than this. But still, it didn't fix the problem. Once I turned the light out and tried to turn it back on, the same thing happened: light remained in the startup phase with that low light.
Afterwards I switched the bulb with a 400W HPS to see if maybe the MH's igniter is the cause, but no... same thing happened with the HPS bulb.
I even bought a NEW 400w switchable balast, it's a white slim one. I forgot to mention that the previous balast was a little old, the big black kind that if something fries in it, it's garbage. SO... NEW balast and the problem is still there: Light not going fully on and even the new balast is making the same loud buzzing sound.
I found out that if I unplug the balast and plug it back on a couple of times, the light turns ON and it remains that way unless I turn it off. So my plants are now under a 24/0 schedule. I tried adding a timer to it, to see if the timer is able to somehow buffer the problem, and it worked. Well... it did once :D, judging by how the light reacts to turn on/turn off, I'm not willing to take that bet during flowering.

Any advice is greatly appreciated, I'm shooting blanks here :D Thank you!
 
Top