ablebravo wrote:

what is best generic part for this application? ie i need to narrow
down 100's they offer to what i need in some way. was looking at
fastron epoxy mcc/n series. can't find the exact values, either. can
get w/in 20-30 MH. how critical?

Not very, though it will change the filter frequencies by a little bit.
They aren't super sharp, though.

How did the inductors fail, though? They hardly ever do, unless a cap
fails and throws DC on them.

schemo gives two 'filters' (choke/inductor) valued at 175MH and
360MH. also in the package are two mica caps .006mfd and .011mfd.

Miller makes some inductors in that range that Digi-Key stocks. If you
want to be right on, get larger ones than you need and take off winds
until the value is correct. Higher current inductors are easy to do this
with.

the values seem hard to find for micas -- is 'orange dip' substitution
for this ok? i can turn up these micas up on mouser but at $6-25 (!)
each, depending on specs.

Yes, but again, mica caps don't fail easily.

What makes you think these are bad?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

whole package broke loose and bounced around in shipping -- leads
damaged, mounting ear broken off. this was a surface mount package
screwed to the chassis top. caps when tested, way off value. thought
best to rebuild whole thing. did not know micas in these values so
expensive, as had only purchased low pf's before. also didn't know i
would be getting into 'choke lore'. live and learn.

ab

"ablebravo" ) writes:
whole package broke loose and bounced around in shipping -- leads
damaged, mounting ear broken off. this was a surface mount package
screwed to the chassis top. caps when tested, way off value. thought
best to rebuild whole thing. did not know micas in these values so
expensive, as had only purchased low pf's before. also didn't know i
would be getting into 'choke lore'. live and learn.

ab

But in the old days, there wasn't much choice but mica capacitors for
precision capacitors.

Likely things have improved, though I don't know if the other choices
are less expensive. Things like polystyrene capacitors have come
along in recent decades, and that sort of thing may be the place
to look.

What you don't want is a capacitor that has really large variation
between capacitors of the same nominal value, or likely capacitors
that change a lot with temperature.

Michael VE2BVW