Yup that is an issue, buying parts that you don't even know are the problem to begin with.
Your best bet is googling the most common problem with dead ballasts and replace that specific part if its under $75 and try it out. If it's a no go make sure you can return the item, and then just go and buy a cheap digital one.
I bought a entire kit - 600W Ballast + 1 MH + 1 HPS + 2 Hangers + Timer + Air cooled Hood + Stickers (Lol) for under $200 even 1000Ws are in the low $200. It's probably better to just buy a new digital one that has a 5+ year warranty than trying to fix a loud magnetic one that can interfere with signals.
When I first started I used a Magnetic and hated the noise and the heat spewing out of that thing.
I went digital JUST last year (7-8 years later) and I was amazed at the difference.
