Quoted from Topcard:
There's good old and bad old. That classic good old pinball smell comes from dry wood, Solenoid dust, a little grease and whatever else. I love that smell! Bad smell comes from a musty old basement that gets into everything including the cloth wire covers. The only true way to get rid of the stench in games like that is to rent an ozone machine.
My first machine I bought back in 2014 or January 2015 (whatever it was) had the bad smell, and pretty sure it had mold on the bottom if not dirt. It was a Chicago Coin Showtime for $300. Talk about a truly terrible deal (look at the playfield on IPDB), but I was pretty excited about it at the time.
I had nowhere to keep it at the time besides in my bedroom. So I slept next to it for around 4 months before I finally realized I should/could move it where I stored my arcade games out here in New Jersey. The seller told me you absolutely cannot tip them backwards so we had such an awful time CARRYING it into the house and fitting it through tight doorways and hallways with the legs on that I didn't want to do it again, then eventually I figured out that you CAN tip them back to handtruck them.
It smelled so bad that I slept on my right side to face away from it, every night, for those 4 months.
It was in an apartment so I'm pretty sure I played it like 2 or 3 times within those 4 months to avoid disturbing the neighbors. So, I quickly resented it. Glad I got it out when I did! I still own it, but it usually doesn't get set up anymore since space is so crucial and for actually good games.