AppleColor Composite Caps

[MdntTrain <js@cimmeri.com>]

  Short story for those, if any, who are curious about the A2M6020
composite monitor.

  My video input jack had become loose, so I removed the female
portion while leaving the vertical ground bracket in place.  I then
installed a regular 1/4" phono jack in the old hole.  Works much
better since you can screw it down.

   Also decided to check all the electrolytics while I was in there.
My monitor was made in Nov 1989.   I tested all in circuit for ESR and
capacitance.  Wasn't able to measure capac. on all.

    As I kinda expected, all the physically large caps had good ESR
and capacity (of those where that showed); and the two smallest ones,
while they generally test higher anyway, these tested abnormally
high.      The single 1uf/250V/85c AEC on the neckboard had very high
ESR (not surprising given its location right next to a regulator with
a large heat sink), and also the one next to the HV cage (1uf/160V)
nestled tightly between a bunch of components.

    I replaced the neckboard with a 1uf/250V/105c AEC, and the other
one with a 1uf/100V monolithic ceramic.  I checked the running voltage
across it and it was only 35V... plus it didn't explode after many
hours of use.

   The moral of this story is that, if you didn't know it already,
caps are starting to go.. beginning with the smallest ones that dry
out the easiest.

   If I'm left with any question here, it's just over how effective is
ESR alone in checking caps?  It's certainly the easiest one to perform
if you have a meter.    But do we also need to be checking for
capacitance and leakage to get a true overall picture of the cap
health?   Or does high ESR tend to go hand-in-hand with leakage or
capac. loss?

  jS