I've had this happen a several times.
Most recent:
TMNT (right around last new years): Game had power cord chopped off. Got it home, looked it over, wired up a new power cord, and plugged it in. Nothing. Checked voltages and determined kill switch was bad. Bypassed it and I was waking my wife up to the theme song as I sung along...loudly!
But my best, most recent experience was a lot of "non working" machines that I bought. The funny part is the guy advertised them here on KLOV but people really didn't bite...at least not like I did. I picked up the following:
- Qbert ~ Supposedly didn't work. Tbbk helped me unload it to my garage. Afterward we looked it over and plugged it in. We heard Qbert speak but saw nothing on the screen. Monitor was dead. Sometime later I wired in a replacement and I was playing Qbert. Works well with only the minor issue of some of the sounds being off.
- Pac man ~ Was missing the monitor. Connected up a new one and it fired up just fine. Worked 100%.
- Battlezone "mini" ~ Seller said before I came down there that he had two Battlezones and one was a mini. It was really just an upright that had the bottom chopped off

. That said, I got it home, fixed a couple loose connections, and it fired right up. The other unchopped upright is missing the monitor so I haven't tested it yet.
The best part is I paid only $300 for all 4 games. The Qbert is in B+/A- shape (needs new CPO and dust removal). Pac man is in pretty nice shape as well. Very little fading at all.