hello,
i have a Metal-halide lamp and the capacitor blow-up often and i don't know why, and what's the solution (without replacing it every month)

ref of lamp:
OSRAM HQI-E 400W/N/SI COATED

 

Osram addresses this in their technical information. I would definitely go straight to them with your question.

 

I chased down 6 links to that reference and none of them even say it HAS a capacitor. If you want to know about the capacitor you will have to put up a better link.

 

Is this your ballast?
https://www.bltdirect.com/product.php?pid=5573&cat=12

 

Yes, this is it.

 

yes it has pal, they all have inductive ballast which requires installing a capacitor.

 

for the price, you can buy the whole kit, which contains transformer and cap. Your transformer may be compromised. Make sure your using the correct bulb, and double check that you're hooked up to the right transformer tap for the voltage.