Help with "micas" identification

[j4570]

These are in a Silvertone 4563 Radio. I'm pretty sure they are original as it was my grandfather's (and their first radio) and no one else worked on it except me I believe.

I restored it (well kinda) about 15 years ago before the internet was around for help. It works pretty well. Been having some hum and other problems lately. I suspect these mica's may not be real mica's

The parts lists has two micas

0.0005 mfd
0.00005 mfd

However, looking at them, I can't indentify these, been to a few websites, but not completely sure.

Pic 1:



Pic 2:



I tried converting the pictures with dots to the mfd (thats microfarad today, or uF, right) in the parts list and I can't get the values to work out.

I'm going to clean up that nasty solder joint while I'm at it too........

I might also replace the electrolytics I used before with under the chassis modern ones. I used some repair ones from Frontier 15 years ago, and I'm sure they are fine, I just don't like how I had to mount one outside the chassis.

Any help with the "micas" I'd appreciate. Info on the web says one is molded paper? The one with the brown dot.

Thanks,

Jason

[sean]

The first one (green-black-brown = 50 x 10^1 pF) would be a 500pF or 0.0005uF cap. The second one (green-black-black = 50 x 10^0 pF) would be 50pF or 0.00005uF.

[j4570]

I was reading the first one brown black green based on the arrows. How do I tell which way to read?

[j4570]

Looking at the schematic, what you said is spot on!

It was that first cap that is giving me fits.

[bandersen]

Originally Posted by j4570

I was reading the first one brown black green based on the arrows. How do I tell which way to read?

Check this out: http://www.tpub.com/neets/book2/3g.htm

[j4570]

I used that website. What am I doing wrong?:

1st "mica"

Brown-Black-Green-Yellow
Molded Paper-0-5-10,000

5x10,000=50,000pF

2nd "mica"

Green-Black-Black
5-0-1

50x1=50pF=0.00005uF

Thanks,

Jason

[bandersen]

Hmm. I see what you mean. Maybe there's more than one dot format ?

[j4570]

Of course,

since I have the schematic, and know what the two values are, and can be sure about the 3 dot, that leaves this mystery one.

Also, it makes no sense that they would start with "05" and then use a multiplier larger. why not start with "50" and use a smaller multiplier.

I think these micas are fun. I found a table (but no pics but a diagram) in an old supreme electronic radio repair manual that shows a bunch of wierd stuff but nothing that matches this.

I'm thinking it's a factory goof. Probably pretty common in the day. Friday afternoon made cap.

Oh well, since I'm pretty sure I know what I have and everyone seems to have consensus on the 3 dot, I'll go with that.

I may haul the old caps into work after I change them, I think one of our techs in the lab has a meter with capacitance. If they are still good.

Jason