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So I'm replacing the caps - Printable Version

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So I'm replacing the caps - standardtwin - 08-19-2014

on my 42-380

Now I ordered caps and of course the conversion needs to take place (why you can't simply say I want .01 mfd, I haven't a clue) grrrrr

Anyway, I had already done the electrolytics, and that woke the set up again. OK, so now I start by replacing the volume pot .01mfd. What I had gotten from canada said 10pf, and the caps are a small clear affair saying 10K on them. I replaced the old one and fired it up. Mind you I am doing one at a time and repowering to check. The volume dropped to a very low level. I then put the old one back and it was restored. Hmmmmm. I had also replaced the tone control .006 with a .0068 yellow one. That now doesn't do anything...

So question is
1. Do I have the wrong value caps
2. I would think so, since volume is restored
3. Are caps besides electrolytics directional?

Thank you from the newbie!!

Mike

RE: So I'm replacing the caps - morzh - 08-19-2014

1. caps other than lytics are not polarised.
2. Caps are alo characterized by working voltage, get it wrong and it will blow up.
3. 10pF is 1/10,000 of 0.01uF.
4. Volume pot is a resistor and not a capacitor.

RE: So I'm replacing the caps - standardtwin - 08-19-2014

I realize now, that I bought the wrong values.

Again, the conversions are a PIA.........

I had the correct voltage though........

Back to the drawing board......

RE: So I'm replacing the caps - Arran - 08-19-2014

Hi;
A lot of the new poly film caps are not marked in microfarads or even with uF, they like marking things like 10K on them, which makes it sound like a resistor, but actually stands for 10,000 picofarads. Why they do this I have no idea, some are still marked in microfarads, electrolytic caps are still marked in microfarads, all it does is add confusion.
Regards
Arran

RE: So I'm replacing the caps - PAradiogeek - 08-19-2014

I've also seen numbers such as 223 for 22,000 pF (thats 22, followed by 3 more zeros). Pico Farads seems to be the standard unit of measure for caps other than electrolytics. I always have to write it out to convert pF to uF. I agree, this is sort of a PITA.

RE: So I'm replacing the caps - morzh - 08-19-2014

Axial Film caps are usaly marked directly (no multiplier) in uF (0.022uF or such) and so are electrolytics.
Ceramics are in pF and use multiplier, so 102 is 1nF, 104 is 100nF, 105 is 1uF etc.
Radial films are mostly marked same as ceramics.

RE: So I'm replacing the caps - David - 08-20-2014

Good afternoon, I must admit to using a great cheat sheet when trying to figure out all the new cap values. http://www.turretboards.com/ look under links you will find cap conversion chart this has saved my bacon more than once. Have a copy on the wall of my work bench. i just do not do this stuff enough to keep in my brain. Hope this helps David

RE: So I'm replacing the caps - Kestas - 08-20-2014

Do you have the schematic for your unit? Having one would be a big help.

RE: So I'm replacing the caps - exray - 08-20-2014

Quote:canada said 10pf, and the caps are a small clear affair saying 10K on them

Small and clear sounds suspiciously like a polystyrene cap. In that case 10K would probably indicate 10pf with a K tolerance (10%).
"the place in Canada" orderlist doesn't require conversion. .01 is plainly listed under several different types. For older values like .05 you will have to make the next closest selection which would be .047 in the 'new' values.

What you receive for a .01 will probably be marked as 103K. He often includes a little chart for that connection and there is a chart on his site.

http://www.justradios.com/uFnFpF.html

RE: So I'm replacing the caps - standardtwin - 08-20-2014

Thanks fellows...

Obviously need better eyes to order the correct values.....Icon_eek

Will have to do so and try again......

I have a very nice layout to read from for the radio..

RE: So I'm replacing the caps - tom.seeger - 08-21-2014

I didn't think you could get 10pF in polystyrene. I think 10K might be 10000pF which is 0.01uF. But in any case be careful with the clear polystyrenes they melt faster than ice cream. So don't solder too close to the body. Maybe that's what went wrong?

RE: So I'm replacing the caps - Arran - 08-21-2014

I find it sort of odd that Just Radios would even carry polystyrene capacitors, those are not very common anymore. They used to use those in German sets of the 1950s and 60s as a substitute for mica caps so I'm not even sure that they are still being made. Precision ceramic, with a zero temperature coefficient, has largely replaced both mica and polystyrene capacitors these days, except for high frequency stuff.
Regards
Arran