To cc I under stand that I need to double the value of the cap and 2 in series .
The question I have is If I can not find the value I need the print
witch shows I need to double the value of 18 uf x2 = 36uf example-- can a 33uf in series with a 39 work or do I need t parallel 2 cap to = 36 using 4 caps ?
(i) Please use the word "which" from now on .
(ii) The final value of all capacitors wired in series, is found by totaling their reciprocal ( "1/x" ) values ( this formula works for 2 or more caps ) .
eg ; Total Capacitance of 39uF & 33uF in series ?
> 1/39 ( 0.25641026 ) + 1/33 ( 0.03030303 ) = ( 0.055944056 ) = 17.875 ( which is close enough in most applications )
(iii) What you might want to calculate ( assuming one has a 33uF cap ) is found by this math ;
1/18 ( 0.055555556 ) minus 1/33 ( 0.03030303 ) = ( 0.025252525 ) = 39.6 ( uF ) to be exact
or if one has a 39uF cap , then ;
1/18 ( 0.055555556 ) minus 1/39 ( 0.0256441026 ) = ( 0.02991453 ) = 33.43 ( uF )
> Those odd values can be arrived at by paralleling small value caps onto the larger cap ( as mentioned by Lee ) .