Now that all the coils are cleaned up, it's time to refurbish them electrically. First, I always make sure that a new coil sleeve moves freely through the hole in the coil body. If the coil sleeve hangs up at all (swelling due to heat damage) then I purchase a replacement coil. The next thing to check is the coil's resistance, which is measured using a multi-meter as shown below:
Coil Ohms (resized).JPG
A zero reading means I purchase a replacement coil, but how do I know what non-zero reading is acceptable? Well, if you aren't familiar with Flippers.com, it's a very handy site. Their coil resistance chart can be used to determine what your coil's resistance should be. In this case, I'm working with an AN-26-1200, which should read somewhere around 12.5 ohms. So, I'm in the ball park at 11.1 ohms, making this coil a keeper.
Here's a link to the coil resistance chart:
https://www.flippers.com/coil-resistance.html
99% of the time I find coils can be reused with no issues. With that said, I do tend to replace the flipper coils as they see the most wear and tear.
Now here's where the fun begins. I ALWAYS REPLACE THE DIODES. There is nothing worse than trouble shooting a flaky diode - been there done that and don't want to do it again It's a pain in the ass to change them out, but they are so cheap ($.02/per diode) it's stupid not to do it. Props to Vid for turning me on to Tayda Electronics; the best price source I've found for 1N4004 diodes, which can be used to replace all the coil and switch diodes in early 80s Bally machines.
https://www.taydaelectronics.com/diodes/standard/1n4004-diode-1a-400v.html
First, I de-solder the coil lugs with my FR-300 (This gun is the sh@t - if you don't have one you should consider picking one up):
Hakko FR300 (resized).JPG
Removing Solder1 (resized).JPG
Now I carefully cut and remove the diode as well as it's leads. You might be asking, "Why can't I just test the diode and leave it alone?" That's the problem; you have to remove the diode to test it, so might as well replace it.
1N4004 Diodes (resized).JPG
Prior to installing, I always confirm that each replacement diode is operating correctly as shown below:
Diode Test (resized).JPG
Solder the new diode to the coil lugs (make sure the band is pointing towards the left "hot" lug). Yes, the diode can be installed backwards - Don't do that. Now, retest the coil's resistance as a final check. Presto - you have a new coil for 2 cents
Restored Coil (resized).JPG
Now it just needs a new coil wrapper.