I don’t like using a file on points as it usually scratches them leaving a rough surface, which is what you don’t want on them. When dressing them, I use progressively finer and finer wet and dry paper until they have a really smooth mirror like finish. 1200 grit is usually good for the final finish. The paper must be placed on a flat and hard surface and I find a flat steel paint stir stick works good for this. The crater doesn’t have to be completely removed but the high deposit on the other point does. Light use of a file here to remove it is OK and a fine diamond stone works to followed by the wet and dry. The points usually have a thin layer of tungsten alloy on them so you can only dress them so many times before you get into the base metal. A good cleaning with lacquer thinner or contact cleaner will remove any oil or residue from the polishing process.
Yeah, I know, people have been filing points since the wheel was invented but I’m a Virgo and my OCD really kicks in around electrical things, or just about anything else to do with a motor but they must be clean, really clean to work properly.
I notice your old cap is reading .33 uF, far above the original value but typical of old outboard caps. The values of them always seem to rise with age while the values of electrolytic caps used in receivers and amplifiers tend to drop in value with age.
Not sure if it matters or not but your new cap is reading .20 uF, slightly more than the 10% allowable above the maximum .14 – .18 uF shown in Garry’s list for the Mark 25 equipped with a Phelon mag. The motor should run fine but the points may pit a bit quicker than if it was in the .14 – .18 range. I can’t remember what way it goes but one point will pit with too high capacitance while the other one will pit with too low capacitance. The engineers who designed the mag specified a cap with a rating right in the middle, minimal arcing or buildup on either point surface while still delivering a strong spark. If your points pit in a short time, you can always try a Vishay cap with a 0.15 uF rating to see if it improves.
