by BIG E » Sun Jun 15, 2014 12:20 pm
I've used J-B Weld on dozens of resistors, and it works just great. I also was concerned at first about the metal content in the epoxy, and called the company directly before coating my first resistor. They understood completely what I was talking about and reassured me I had nothing to worry about for this application, that the actual metal content in the product was very small and would not cause any electrical problems.
I believe Parma's current "Wet Wound" series of resistors may use a similar epoxy type product.
As for the ceramic resistor coating, I haven't seen the Parma stuff for years, and my last bottle dried up decades ago. I don't remember if it was available back in the late 1980's when I had my own commercial raceway. I think that's about the time I heard of the idea to use J-B Weld to repair customer, rental, and my own controllers. Anyone remember buying the brush on rubber coating Parma used to sell in the 1970's to paint over the metal triggers?
We all used it as an insulator to heat build up (this was before Parma's "Turbo" series of controllers with their Lexan and then nylon triggers).
Once the J-B Weld is applied and dried completely to a nice smooth finish, I believe it's actually better than the original factory ceramic coating.
I use a standard Sharpie marker pen to identify the ohm rating, date, or any other info directly on the epoxy of the resistor once it's ready for use.
You can even paint it if you like, but beware -- if you're in the habit of running a hot (temperature) controller, the paint will only make things worse.
I've never tried to dye the epoxy when mixing it, and I don't know if that's even possible.
And of course, this coating process works equally well on both single and double "barrel" resistors.
Hope this information helps to save some resistors and $$$! -- Enjoy the hobby, guys... Ernie