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 Post subject: Capacitor Value
PostPosted: Jun Fri 07, 2019 2:22 am 
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I need help identifying the value of these two molded capacitors. The one in the first image looks to be a .0032 mfd but unsure of the rated voltage, and the second one the first three dots are just blank. Any help?

The wiring schematic also doesn't match the radio, but know it was working before hand. So I am matching the values currently in the radio for now.


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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 2:42 am 
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Tables, calculation and fourth color voltages...
http://antiqueradios.com/forums/viewtop ... 4#p2413184

and... restuffing by gary rabbitt... :)

Greg.

oh... Micamold is a brand name.
Many domino capacitors were/are paper-capacitors. Do not rotate them on their axis.


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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 2:54 am 
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I have the tables, but like I said the bottom image, the first three dots are just blank.


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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 3:59 am 
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With respect, your photo is too small, dark and out of focus. I can't see the arrow.

I know what you wrote, but, what is the make and model of your radio and where/what are they connected to?

If you process your images through picresize.com - you can shoot-up an 800px wide photo to the thread.
Posting photos to a forum thread...
The skinny: viewtopic.php?p=3032571#p3032571

Greg.


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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 5:28 am 
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First one might be .022 uF (2-2-3). If the value is actually that high, it's probably not a mica capacitor (paper inside). Second one looks like .0015 (1-5-2).

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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 2:08 pm 
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Well, I can take better photos when I am home later.

However I can explain it for now.

The first image the arrow is left to right, going orange-red-red.No forth dot to indicate voltage.

The second the top arrow is right to left, all blank. The second row is left to right, red-green-brown.

I am mostly confused on the blank spaces of the six dot molded cap.

The three dot one is a 0.0032mfd but I can likely assume the rated voltage 1000v since that is highest I saw in the radio, but wanted to make sure before ordering.


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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 3:19 pm 
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Looks like the lettering of “Micamold” also helps define the direction, so I think you’re right that the first is 3200 pF. That’s an odd value but must be correct. Maybe a padder capacitor?

The second one then would appear to be 250 pF.

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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 4:08 pm 
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Dennis wrote: viewtopic.php?p=1296489#p1296489

and...
Tom wrote: https://www.radiomuseum.org/forum/crosl ... ode.html#6

:) Greg.


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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 4:29 pm 
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BBohler wrote:
The first image the arrow is left to right, going orange-red-red.
32 is not a standard value, more likely 22000 pfd.

BBohler wrote:
No forth dot to indicate voltage.
If voltage is not given, it's 500 volts.
That was standard for mica "domino" capacitors.

BBohler wrote:
The second the top arrow is right to left, all blank.
The second row is left to right, red-green-brown.
That's 250 pfd.

It's not unusual to find dot positions that are not used.

- Leigh

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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 4:40 pm 
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What radio, year, and model might help. I know you said the schematic is no help, but knowing what radio and year might help as others may have the same radio..

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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 4:59 pm 
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Leigh wrote:
BBohler wrote:
The first image the arrow is left to right, going orange-red-red.
32 is not a standard value, more likely 22000 pfd.


So they color coded it backwards?

Leigh wrote:
BBohler wrote:
The second the top arrow is right to left, all blank.
The second row is left to right, red-green-brown.
That's 250 pfd.

It's not unusual to find dot positions that are not used.

Ah good to know, thanks.

pauls.ironhorse wrote:
What radio, year, and model might help. I know you said the schematic is no help, but knowing what radio and year might help as others may have the same radio..

It is a Sparton 68 from around 34-35


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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 6:12 pm 
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Image

Large schematic→ https://a4.pbase.com/o12/56/215056/1/16 ... titled.png

To convert from μF to pF
Here's a handy capacitor conversion chart.
http://justradios.com/uFnFpF.html

μF (microfarad)
pF (picofarad)

Random examples...
.002μF (microfarad) equals 2000pF (picofarad)
.00025μF equals 250pF


Greg.


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 Post subject: Re: Capacitor Value
PostPosted: Jun Fri 07, 2019 6:39 pm 
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BBohler wrote:
Leigh wrote:
BBohler wrote:
The first image the arrow is left to right, going orange-red-red.
32 is not a standard value, more likely 22000 pfd.


So they color coded it backwards?
The parts list on the schematic that Greg posted does show a .0032mfd capacitor.

So apparently this set predates the value standardization era, or they needed an odd value.

Sorry for the digression.

- Leigh

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 Post subject: Re: Capacitor Value
PostPosted: Jun Sat 08, 2019 12:32 am 
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Fixed value padder capacitors tend to have odd values, and be fairly large micas like this one. They need to be reasonably stable to prevent tuning drift, and the odd value is needed so that the dial span covers the intended range and tracks with the other tuning gang, which is frequency shifted by the IF frequency.

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 Post subject: Re: Capacitor Value
PostPosted: Jun Sat 08, 2019 1:37 am 
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Tom Albrecht wrote:
Fixed value padder capacitors tend to have odd values, and be fairly large micas like this one. They need to be reasonably stable to prevent tuning drift, and the odd value is needed so that the dial span covers the intended range and tracks with the other tuning gang, which is frequency shifted by the IF frequency.


Oh I thought they were molded paper type, then if it's mica there is no need to worry then.

However I found I over looked one capacitor at the top of the chassis. It is a micamold as well, but a large cylinder style, threaded base with three wires, Red, White (Maybe yellow), and black out of the bottom. The label isn't in great shape, but tried to do a better job with the picture.

Am I just blind and missing the mfd value?


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 Post subject: Re: Capacitor Value
PostPosted: Jun Sat 08, 2019 1:46 am 
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That’s a dual section electrolytic cap. C13 on your diagram. Two sections of 8 uF each. You can replace it with two separate 10 uF 450 V electrolytics. If you want to play it safe, use 500 V electrolytics, even though the originals were 450 V.

I don’t think I’ve seen one of those made by Micamold before.

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 Post subject: Re: Capacitor Value
PostPosted: Jun Sat 08, 2019 2:08 am 
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The two eights appear to be under the orange marking.
Is the original rating (working voltage) not 480V?

Greg.


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 Post subject: Re: Capacitor Value
PostPosted: Jun Sat 08, 2019 2:23 am 
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Ah, Thanks for the help.


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 Post subject: Re: Capacitor Value
PostPosted: Jun Sat 08, 2019 3:39 am 
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Enlarged picture, is not 460 V.W.. mean 460 voltage working, and 525 V.S.P mean 525 Volts Surge Protection ? (All on the same line)


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 Post subject: Re: Capacitor Value
PostPosted: Jun Sat 08, 2019 3:59 am 
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V.W. volts working.

Working Voltage. The (usually maximum) voltage at which a circuit or device can be operated continuously with safety and reliability.

V.S.P. I think is voltage supply peak.

:) Greg.


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