[Boatanchors] Recapping receivers - further thoughts

[Arthur Shulman]

Just a note to reinforce the excellent advice that has already been
posted here:

Replace the HV electrolytics before attempting to operate the receiver.
You really do risk a fried transformer or choke if these are defective.
Install a properly rated fuse if not already present.

Paper caps do have a built-in failure mechanism - they can be replaced
with high-quality film or mylar caps without regret.

If any were defective, they may damage adjacent resistors - not a bad
idea to measure these with the cap out to see if any have changed value
- use an accurate meter. Look for an unevenly darkened resistor body or
obviously damaged color-code paint as a hint of overheating.

Disk caps seldom fail, but if they do, they should be replaced with new
disks.

Mica caps were usually used where temperature stability or a special
value was required. These should generally be left alone unless
definitely proven defective or the case is split. Reading the values
from the code can be problematic especially if temperature compensation
was involved in the selection. Getting a new EXACT replacement can be
next to impossible!

I make a point of not even disturbing the physical positioning of mica
or disk caps if used in RF/IF tuned circuits, let alone replace them.
(Unless PROVEN bad!)

You forgot to mention 'dogbone' or radial-lead encapsulated ceramic caps
- same protocol as micas. Leave them alone unless proven bad.

Never replace mica or ceramic caps with any other type - they have
different HF characteristics.

Take notes & only replace one cap at a time, testing results after each
replacement, and correcting any problem before continuing.

Arthur Shulman VE3ZV