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 Capacitor Conversion Questions

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kjw

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PostSubject: Capacitor Conversion Questions   Thu Oct 21, 2010 9:08 pm

I just received my caps and schematics from justradios.com for my belmont model 636. I have questions about how to convert the capacitors. The problem is I have a bunch of capacitors and they all have different #'s than what are on the schematic. I did do a little research and found some conversion charts but I do not completely understand how to use them. If anyone can help explain this to me I would really appreciate it.
From what I gather the schematics for both belmont model 636 Series A & B have 11 caps highlighted that need to be changed out. The series B has a few lytic caps that are slightly different values than the series A. I can see from the 2 schematics provided what the difference between the series A & B are, so I will determine that when I remove the chassis.

Here are the Cap Values for Series A:

.02 x 400 v.
.1 x 400 v.
.25 x 200 v.
.05 x 200 v.
.003 x 600 v.
.2 x 400 v.
30 mfd. lytic-150 w.v.
30 mfd. lytic-150 w.v.
.01 x 200 v.
40mfd. -25 w.v. lytic
.02 x 400 v.

The Series B Values:

02 x 400 v.
.1 x 400 v.
.25 x 200 v.
.05 x 200 v.
.003 x 600 v.
.2 x 400 v.
20 mfd. lytic-150 w.v.
40 mfd. lytic-150 w.v.
.01 x 200 v.
20 mfd.-150 w.v. lytic
.02 x 40 mfd. - 25 w.v. lytic

Listed below are a few of the caps I received today.

MIEC 85 degrees C 40uF 160v
MIEC 85 degrees C 30uF 160v
ETR MET 503k 630v
ETR DME 503K 630V

I still have more questions but I will try and ask them a couple at a time.

Thanks for any help in advance. Kris
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oakdust



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PostSubject: Re: Capacitor Conversion Questions   Thu Oct 21, 2010 9:12 pm

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kjw

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PostSubject: Re: Capacitor Conversion Questions   Thu Oct 21, 2010 9:21 pm

Thanks Oakdust, I checked out the site and still can not figure it out.

What would be the conversion for this cap? MIEC 85 degrees C 40uF 160v
I think I can figure it out if I know the conversion for 1 of them.

Also is it possible the values of the caps I received will not be exact matches to the values listed for the radio?

Thanks, Kris


Last edited by kjw on Thu Oct 21, 2010 9:49 pm; edited 1 time in total
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kjw

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PostSubject: Re: Capacitor Conversion Questions   Thu Oct 21, 2010 9:36 pm

.05uF x 200 v. = ETR MET 503k 630v

Would this work or is the Voltage to high? and is the .05uF = to 503k ?
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pixellany



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PostSubject: Re: Capacitor Conversion Questions   Thu Oct 21, 2010 9:51 pm

Don't worry about the voltage being too high. This is the maximum allowable voltage before breakdown or leakage. Anything below the the rated voltage is OK, but people usually have some margin (eg never run a 630-volt cap above maybe 400-500volts.

503K means 50,000pf (5,0,and 3 zeros), 50,000pf = 0.05uf
203K = 0.02uf
504K = 0.4uf
etc.
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kjw

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PostSubject: Re: Capacitor Conversion Questions   Thu Oct 21, 2010 9:54 pm

I think that explained it to me, I was trying to make it more complicated than it actually is. Thank you for the help Pixellany. Kris
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Alan Douglas



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PostSubject: Re: Capacitor Conversion Questions   Fri Oct 22, 2010 10:19 am

"K" indicates 10% tolerance (J=5%)
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kjw

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PostSubject: Re: Capacitor Conversion Questions   Fri Oct 22, 2010 10:52 am

Alan Douglas wrote:
"K" indicates 10% tolerance (J=5%)

Please elaborate this a little more if you can. I am completely new to this.

Thank you, Kris
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ggregg



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PostSubject: Re: Capacitor Conversion Questions   Fri Oct 22, 2010 11:10 am

Allen is saying that the tolerance is the variation the part is allowed to have when manufactured. A lower number is better.
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kjw

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PostSubject: Re: Capacitor Conversion Questions   Fri Oct 22, 2010 11:30 am

If I am understanding correctly I can be 10% off value from what is stated on the schematic for a K cap and 5% off value with a J cap and a lower value is better. Is this correct? Thanks for the help Allen and Greg.

Kris
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Radiosmoker

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PostSubject: Re: Capacitor Conversion Questions   Fri Oct 22, 2010 1:56 pm

Unless the schematic specifies the % of tolerance required then,
Most caps will be 20%
So if you have a 20ufd, at20% tolerance it could be as low as

20ufd times .2 = 4

Subtract 4 from 20 = 16
and
Add 4 to 20 = 24

So at 20 % tolerance your capacitor could be in the range of 16 to 24 ufd.
That is acceptable.

Hope this helps.

In an oscillator or RF section you may find tighter or closer tolerances such as 10% -5% or 1%

Rather than express your question as is a lower value better, (that gives the impression that the lower capacitance value is better). That answer is no.

If on the other hand had you meant is a lower rather than or closer or tighter tolerance value better, then you are asking is less of a tolerance better, then the answer is also no.

What you are really asking is, using a tighter tolerance specification better, then yes.

A 20ufd capacitor with 20% tolerance is not as good as a 10% tolerance in capacitance. As far a precise or precision value.

It's a game of semantics I guess, but I did understand your question. But being specific in your wording will help in receiving the answer needed.

Your phrasing is OK up to a point, It's just that a reader might take the question on face value, rather than the intent behind it, And boy do we have some sticklers here for that issue. Embarassed

So in essence a 5% is better than a 20% in design or use.
The same thing in resistors. Make a bunch of resistors and measure them and sort by tolerance values measured.

I had nothing better to do, so I just am expressing my humble opinion, not that I am right.
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