#16
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Quote:
jr Last edited by jr_tech; 05-10-2014 at 10:24 PM. |
#17
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Yes, replacing the 200 pF cap was one of the first things I tried. The mica cap that was in there wasn't the problem. Well, that does make me wonder if the switch contact is bad. I'll have to check that again sometime.
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#18
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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....
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#19
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jr |
#20
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Quote:
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.
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
Audiokarma |
#21
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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).
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#22
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Yes, I have read that the units came out with the 25V being high. I don't have much concern with such low voltage applications, but I will bear that in mind. I am noticing that the more I play with the thing, the closer the values are getting. Probably caps reforming as I use the unit.
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#23
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The link in my original post ( I just fixed it) talks about several issues link like the 25V/45V problem. There aren't really that many caps to replace on one of these units. I did check and for the reference caps connected to the range switch I did use 1 and 2 % units for accuracy. By the way, a leaky cap reads as though it has higher capacitance than it really does. Its the way the bridge circuit works. Then also on large electrolytic s the PF control needs to be adjusted.
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#24
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[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.
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
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