Question about MH lighting

A few days ago a growing friend gave me his old 400watt MH hydrofarm grow light with a built in ballast. So I went out and bought a 400watt MH light that fits the requirements listed on the growlight. Now when I went to turn on the light it didn't come on right away, which I wasn't worried as I've heard it can take up to 5mins. But after 10mins it never came on, same after 30mins and a hour. I checked the bulb while it was in and turned on and inside the middle part there was like a little flicker that looked like it was trying to ignite the bulb and get it lit up, however it never came on. Now Im wondering if its the bulb that has something wrong with it, or if its the grow light its self? Any help would be much app as my buddy is not around to answer my question.

How sure are you it's a MH and not HPS?

How sure are you it's 400w and not a 250w? Most (but not all) of the hood/transformer sets are only 175 to 250w at most.

If if is a 400w MH and your new bulb does not light then the I would assume your cap is bad and needs to be replaced.

Just a guess

On the side of the light it says Hydrofarm, 400watt 120v 4.0a 60z and says use only 400watt Metal Halide bulbs M59 type lamp. When I also got it from the friend he still had a old burned out 400watt metal halide bulb in there, i bought the same bulb that was in it. What is the cap and how can I replace it? Unsure of that one.

Also, not sure if this matters but I can hear the ballast humming inside the light when i turn it on. Planning on returning the bulb in the next hour to double check if its the bulb, but I still am unsure what the cap is and where to locate it and replace it?

1 are all conections tight and clean
2 is the tit on the mogle base not burnt
3 is the bulb in the right direction U universal, V vertical H horizonal
4 have you replaced the bulb with a new one, you always need a spare
5 bulbs usualy take about 3-5 min. to fire up, and there is alway a flicker in the starting globe.
I would just get another bulb and test it. I have ballast and caps that are over 25 years old and no problems.
O yea always clean you bulb before use and leave NO finger prints.

Easy as pie to test the capacitor...Although finding replacements is not always simple.

You can test the capacitor with an analog-type ohmmeter, set at a high resistance scale. Turn off the circuit power first; then discharge the capacitor by placing a screwdriver or other piece of metal across its terminals.

Now, you disconnect the capacitor from the circuit. Connect the meter's test leads to each terminal. If the ohmmeter measures a high resistance, the capacitor is open and you should replace it. If the reading is zero or a low resistance, the capacitor is shorted. Again, you should replace it. If the reading is zero or a very low resistance initially and the resistance slowly increases, the capacitor is good.

Well what I ended up doing was giving it back to my grow buddy. He said he'd like to try and fix it. So what I ended up doing was buying his custom light he made for $100. It has a 400watt MH and 400watt HPS in the same fixture. Now i just need to work on keeping the room cool.

Hey, make sure you have enough wattage to run it fully where ever you plug it in my lights (also MH) doubled in intensity when i fixed the electrical output.