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 Post subject: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 4:50 pm 
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Happy Thanksgiving!

I have a El Menco set of capacitors that I'm not sure I'm reading right. I'm getting aprox. 0.542 nf readings on two and .0395 on the other two... they are out of a 12s266 and a 12s265. Brown, Black, Green. Is this a 100pf capacitor?


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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 5:04 pm 
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Hi. I think you are reading backwards.
Brown=1
Black=0
Green=5

So brown,black,green "1000000" which would be 1uF

Much more likely is green,black,brown or "500" which would be 500pF

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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 5:17 pm 
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Bosch's Fault wrote:
Hi. I think you are reading backwards.
Brown=1
Black=0
Green=5
So brown,black,green "1000000" which would be 1uF
Much more likely is green,black,brown or "500" which would be 500pF

A 1mfd mica cap would be huge.

I think 500pf is MUCH more probable than 1mfd.
500pf is quite close to his readings on two of the caps.
I don't understand the readings on the other two.

- Leigh

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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 5:33 pm 
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What position are they in the circuit, what is the C number on the factory schematic? That should give you some idea what to expect. They were probably OK and should have been left alone, but once you disturb the leads on mica capacitors, they should be replaced because movement frequently causes internal damage.

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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 5:38 pm 
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I thought I was reading it backwards too, but the green dot is pointing to the right...?
and whats interesting is that the two on the right from the 12s265 are consistent at .542 ish
while the two on the left were consistent at .046 nf ish...until I pushed down on the bottom ones leads and it
read .512 also.


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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 5:42 pm 
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Good indication that the leads have broken connection inside, caused by disturbing the position of the part.

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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 5:50 pm 
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I did recently have one of these caps that was intermittent prior to moving the leads. Regardless usually want to replace these with an accurate value to what is called out on the schematic / parts listing.

Good luck

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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 5:52 pm 
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The two on the left came from a very disturbed 12s266, the right from a original 12s265.
One cap runs from the volume control to pin 8 of the 6h6, other runs off pin 3 of the 6j5..
So, is that C-16..?
I'm still learning schematic, so my apologies on my ignorance.
http://www.nostalgiaair.org/pagesbymode ... 024735.pdf


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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 6:43 pm 
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Both of those would be C12, 500 pf.

Note that Zenith often uses the same part ID notation more than once in a schematic when two or more parts have the exact same value and part number, which can be confusing.

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Dennis

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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 6:59 pm 
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Thank you all for confirmation on that. When in doubt, inquire here. You guys are great!

But I'm still confused as to why the green dot points right, yet is read in reverse...?
I've looked up many charts but couldn't find anything matching these El Menco's;
http://www.radioremembered.org/capcode.htm


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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 9:07 pm 
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Flash wrote:
But I'm still confused as to why the green dot points right, yet is read in reverse...?
I've looked up many charts but couldn't find anything matching these El Menco's;

When I wrote my color-code decoding program I researched mica caps in considerable detail.

There were about a dozen "standard" codes, meaning used by more than one company.

Then there were an unknown number of proprietary codes used by only one company.

That webpage is interesting but nowhere near complete.

Arrows normally point in the direction in which the code is read. If it points to the right, you read left-to-right. But that was not standardized either.

- Leigh

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Click "Grebe Stuff" for Synchrophase info


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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 10:30 pm 
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Leigh,
Thank you.
I would like that color-decoding program. Where might I find it?

Since now I don't trust my decoding... is this a .005 Micamold cap.? Green, Black, Red.
Have two that read around 8.0 nf. I figured they went high with age and should be 5.0 nf
Am I calculating this one right?


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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 10:46 pm 
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Yep, .005, digital meter doen't like leaking caps and tell lies about value...

A bridge is better, least expensive alternative for determining value. Even a bridge will fail when the cap is severely leaking...


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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 10:56 pm 
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Chas,
Great! Thanks. I got one right...feeling better now.. :)


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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 11:06 pm 
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And.............those long rectangular Micamold caps are actually paper inside and always bad.

To make matters even more confusing, if you find a Micamold part with three dots that is rectangular and quite long, but narrower than that capacitor, it will be a wirewound resistor!!

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Dennis

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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Thu 23, 2017 11:35 pm 
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Dennis,
Yes! I have come across one of those nasty little traitors. Drove me nuts until I found out what it was.... :roll:


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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Fri 24, 2017 12:17 am 
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Quote:
while the two on the left were consistent at .046 nf ish

That's the capacitance of the meter leads. As long as you don't move those wires, you should subtract that value from any other capacitance you read. Some meters have a function to do that automatically. But if you move the leads, you have to do it over again.

Since your capacitors measured that value, they were either bad or the probes weren't making good contact, probably due to whatever crud (technical term) was on the capacitor's wires.

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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Fri 24, 2017 12:49 am 
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Jim,

Noted. Thought that had some influence. I'm glad I asked. Never stop learning here....


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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Fri 24, 2017 3:26 am 
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Regarding measurement of low capacitor values...

The capacitance of the test leads can equal or exceed the value of the part.

To determine that value, arrange everything as you would to read the cap value, but connect only one lead to the capacitor. Place the other test clip as close as possible to the other cap lead without touching it.

Note the reading on the meter. Now connect the second test clip to the cap lead and note the reading.
Subtract the first value from the second to get the actual capacitor value.

To maximize the accuracy of this method, the part, the leads, and your hands must move the least possible amount between the two steps. Also, the measurement must NOT be done on a metal surface.

- Leigh

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http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


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 Post subject: Re: Am I reading this capacitor right?
PostPosted: Nov Fri 24, 2017 3:22 pm 
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Leigh,

Great idea. I wondered what was the best way to do that. I'll try that today.

Thanks


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