Resored Heathkit C-3

[Tubejunke]

I haven't yet changed any capacitors in my C-3 wishfully thinking that some reforming may occur. All that is wrong with mine is the values are way off. Anyway, I did take a close look at the switch contacts and they were VERY bad. I had to scrape the crud off of the contacts with a large sewing needle!

Lessons learned: "Works" must mean many things to many people....

[jr_tech]

Originally Posted by Tubejunke

All that is wrong with mine is the values are way off. Anyway, I did take a close look at the switch contacts and they were VERY bad.

Are all resistance and capacitance ranges way off, or just a few? Do you have a can of Deoxit D-5 (or similar cleaner) to clean the contacts? IMHO, the stuff works wonders.
jr

[Tubejunke]

Originally Posted by jr_tech

Are all resistance and capacitance ranges way off, or just a few? Do you have a can of Deoxit D-5 (or similar cleaner) to clean the contacts? IMHO, the stuff works wonders.
jr

Seems like all the capacitance ranges that I have tried are off, but that is limited to larger value electrolytics and then some non polarized units like say .1, .047 uf.ect. I haven't really tried any uuf. or anything like that. I also haven't tried resistance functions as it's not something that I would use much if at all.

About cleaning contacts; I have some contact cleaner, but I doubt that it would have taken off the crud that was on that rotary switch, so I did the bulk of it by hand and then sprayed them off. Also, I cleaned the tube pins and sockets.

At least the leakage function seems to work, which is the most important part and the reason I wanted the unit since modern equipment doesn't use real world voltages to check caps and that is of utmost importance.

[DaveWM]

check the leak voltage esp the 25v, it may be high, maybe high enough to not test correctly if you are testing a 25v cap. I ended up changing a couple resistors in the voltage divider to get a true 25v. I think it was closer to 50v before the change (or just leave it and remember or mark the voltage as 50v or what ever it is if you prefer that higher voltage anyway).

[Tubejunke]

[QUOTE=DaveWM;3106236]check the leak voltage esp the 25v, it may be high

I was placing a volt meter across caps to watch them charge a few nights ago and the 25V was actually spot on. What really worried me was that all of my other voltages were down approximately 100V. I started thinking, OK DC outputs all low (to a point); look around the rectifier. In doing so I found a .25mF cap that was about double in value according to a Fluke DMM. I had a close replacement, but the voltage rating wasn't high enough, so I am going to have to make a list for this and a few other radios I have and see how she acts with a bit of refreshment.

Looking around in there I could see that through the years a few replacements were installed in various places, but the big, nasty wax/paper units (this .25 being one) are all still there. I did go through the resistors while I was in there and all of the old carbon units were within reasonable tolerance.