[R-390] Megger and Capacitor Measuring

[Perry Sandeen via R-390]

List,
 
I agree with Charles that using a megger is generally not a
good way to trouble shoot a radio. It is
cumbersome and uses up an enormous amount to time. Taking
one end out of the circuit risks parts breakage or re-soldering problems.
 
The true value of a megger would be in checking new caps for
a potential
 
My position is if one is working on radio like the *A* or a
SP 600 the most time and cost effective way is a whole sale replacement of all capacitors
EXCEPT some silver mica’s. (The new type, not the old *postage stamp* units.
 
I do this because if one , two or five out of 50 BBOD’s
check OK, how much longer than their current 50 + years are thy going to last?  And generally speaking the new caps are
smaller sized.
 
I believe the same for all the carbon resistors.  Many are known to drift.  It is now even more cost effective to replace
them as Mouser sells the many Vishay .5W 1% odd value metal film resistors that
can be used for 24 cents for single unit with no minimum quantity. Xcion 1%
metal film .5W are 50ppm and 15 cents each but one has to buy them in units of
10. However they are 100 for $6.50 which is ideal if you have several radios to
rehab.
 
Several less obvious benefits  comes with the MF resistors. Circuits using
them will maintain a more stable condition. I’m a great believer of removing
all variables possible. Also as a general rule they are smaller which makes for
easier
 
I readily concede that the process I do takes far more time upfront.  However in the long run-years and years I’m
way ahead.
 
Regards,
 
Perrier