Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 1blueheron on February 25, 2019, 07:39:37 am

Title: Questions on capacitor values
Post by: 1blueheron on February 25, 2019, 07:39:37 am

I have some old capacitors that I am trying to decipher the values from color code on.  I googled it and ended up even more confused so I thought I would put it to the experts.

First problem is which end to start from.  How do I know which band is the first band, and which is the last?

Next question is how do I determine the voltage rating?  A these 4 band caps with a fifth voltage band or 5 band caps without a voltage band? :w2:

Are these what is referred to as bumblebees?  I have a bunch of them.  Are they likely leaky trash that should be thrown out,  or should I go rent a safe deposit box for them :l2: 

thanks!

Title: Re: Questions on capacitor values
Post by: sluckey on February 25, 2019, 08:18:39 am

Start on the left end for those. Your top cap is 27 plus four zeros which is 270000pF, or .27µF. Voltage rating is 200V. Your assignment today is to decipher the others. Don't worry about the tolerance. You will be graded!   :icon_biggrin:

Title: Re: Questions on capacitor values
Post by: 1blueheron on February 25, 2019, 09:25:47 am

OK, here is my exam answers. 

Yellow (4), Violet (7), Orange (000) White (10%),  Yellow (400V) =    47,000pF  =.047uF

Brown (1), Black (0), Orange (000), Black (0%?),  Yellow (400V)=   10,000pF =.010uF

Red(2), Red(2), Red(00), Black(0%?) Blue (600V), =  2200pF = .0022uF

Brown(1),  Black(0), Red (00), Black (0%?), Blue (600V)  = 1000pF = .001uF


I don't have any reference to determine difference between black, and gray.  Assuming black is correct as anything blacker on black background would not be visible?    :w2:

How did you determine to start from the left side?   Does the larger gap in stripes always go to the right?

Title: Re: Questions on capacitor values
Post by: sluckey on February 25, 2019, 09:49:57 am

You aced it dude!

Black is tough on a black body color, so they usually do a dark charcoal gray color. If you ever see a real gray (#8) band you'll know the difference.

The wide space between the 4th and 5th bands is the key... always on the right.

Those are bumblebees. Polish them and put them on eBay!  :icon_biggrin:

Title: Re: Questions on capacitor values
Post by: jjasilli on February 25, 2019, 11:19:23 am

These old gems often leak DC, but can be used where there's no DC to be blocked.  The right values can be used as guitar tone caps.

Title: Re: Questions on capacitor values
Post by: 1blueheron on February 25, 2019, 01:12:22 pm

OK, think I got it thanks to "a little help from my friends" :icon_biggrin:

One more question.... Is there a polarity to these things and if so, which end is -?

Title: Re: Questions on capacitor values
Post by: sluckey on February 25, 2019, 01:33:02 pm

It's not polarized.