Enigmatic Condenser Coding

[Winky Dink]

Please help me read these caps. I figured out the disk on the right: green-black-red, 5000 pF. The confusing thing was that the Wallace manual said the values for mica and ceramic would be in picofarads, but apparently not in this case. Is there a convention for orienting a disk so you know whether you're reading right-left or up-down?

The ceramic on the left baffles me. If you ignore the violet top and the third black stripe, then it reads 20 pF like the schematic specifies. Are the violet top and third black stripe for voltage, tolerance, or....?



Thanks,
Winky

[Tubejunke]

This is a good topic Winky! I hope that your questions are answered and this thread grows to shed light on some other hard to identify capacitors, inductors, etc. Good luck!

[kx250rider]

I don't know how to read it on caps, but for an oblong resistor like that cap, it's "Body-End-Dot" (remember "BED") . So if that were a resistor, it should be 1.7K ohms. The disc I'm not sure at all how to read.

No clue as to how to read the other markings on that oblong cap, and if it weren't for the fact that you have the schematic, I'd have said that's a peaking coil or indictor of some sort.


Charles

[Eric H]

There are various Capacitor Color Code Charts on the Web, it can be hard to find exactly the one you need.

I will say this though, those particular Capacitors are unlikely to be bad in most cases, Mica and Ceramic Caps are very reliable.

[Kevin Kuehn]

Yep, I Googled ceramic capacitor color code.

http://www.google.com/imgres?hl=en&c...9,r:0,s:0,i:75

[Winky Dink]

Before I posted I spent considerable time looking for examples like the image above. There seems to be a pattern that the extra makings, like the end cap color and the fourth color stripe, indicate information in addition to the capacitance value--most likely voltage rating, tolerance, and/or what units to read (mfd or mmfd [pF]). This one, from the same Admiral TV, reads the correct value if you only use the middle three marks. I did see one site that showed color codes for voltage rating, and green would mean 500V max. Brown would be 100V max. So far I haven't had any problem with just leaving the micas and ceramics alone. But I'm only working on my fifth project ever.



Thanks for the comments. If I find definitive answers, I'll post again.

- Winky

[Kevin Kuehn]

Your last picture is a radial lead ceramic.
As per the chart: The end cap color(A) is definitely the temp coefficient(brown = -30).
The green stripe (E) indicates + - 5% tolerance.

[Phil Nelson]

It's good to learn these things, but I would repeat Eric's observation that this type of cap rarely if ever needs replacement. I don't think I have ever replaced one of the types shown in these photos, knock on wood.

I would be especially leery of messing with this type of cap in an RF or IF circuit, since that might force an otherwise unnecessary realignment.

Phil Nelson

[Kevin Kuehn]

I wouldn't change those caps either, unless the circuit is acting up because of one.

[old_tv_nut]

Now that we know the end cap is a temperature coefficient, I concur that it's not good to change these, as they may be compensating something with the opposite coefficient.

[Winky Dink]

I'm the guy who knock the ceramic off the bench, then steps on it when he tries to pick it up. Sometimes they have to be replaced.

Actually, the issue came up when I was trying to decipher a very blurry schematic and needed the values so I could identify components.

Thanks,
Winky