[Jukebox-list] capacitor values

[Jay Hennigan]

rockolakid wrote:
> Hi All,
>           I have had problems with my Rockola 1448 I have located the fault to a faulty capacitor in the control box assembly, there are 4 inside all the same size I want to change them all, the drawing says they are 0.5 MFD, but I am confused by the colour band markings they are yellow/purple/orange/grey/    yellow, the control voltage is 28v dc, can any one on the list explain the markings, does the value add up to 0.5 MFD.

This is the standard color code, similar to resistors.

0 black
1 brown
2 red
3 orange
4 yellow
5 green
6 blue
7 violet
8 grey
9 white

Crude but effective mnemonic:

"Bad boys rape our young girls but Violet gives willingly"

So, the first three bands of 4-7-3 correlate as follows, in picofarads:

4, 7, followed by 3 zeros = 47000 picofarads, equivalent to .047 
microfarads or .05 should be close enough.

The fourth grey band is probably actually white, indicating a tolerance 
of +/- 10%.

The final yellow band is the voltage rating, 400 volts.

A .047 or .05 microfarad, 400 volt or higher capacitor will replace it 
just fine.

The capacitor is almost certainly bad.  These use a spiral of paper and 
foil, and moisture over the years causes a partial short.  I would 
change out all of the "bumblebee" capacitors, especially in the 
amplifier.  Don't throw them away, however.  Keep the leads as long as 
possible and sell them on EBay to the guitar people who pay big bucks 
for them.  These were original equipment in vintage electric guitars and 
they want them authentic.  At the millivolt levels seen in guitars, the 
leakage isn't dangerous.  The sound may be distorted, but distortion 
seems to be a good thing in the case of some electric guitar players.

See also:  http://www.wjoe.com/capacitorinfo2.htm

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
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