I need some of the wisdom of the group. I started to have the
thunderstorm crash type of noise on all freq on my SX 100. I know this
is indicative of silver mica disease in the IF's when they have the
embedded mica caps built into the bottom base of the xfmr. Does this
also happen with discrete mica caps in the IF xfmrs like in this rcvr?
Any other ideas on possible causes? Thanks for the help. Mike KF6KXG

In article ,
tchrme wrote:
I need some of the wisdom of the group. I started to have the
thunderstorm crash type of noise on all freq on my SX 100. I know this
is indicative of silver mica disease in the IF's when they have the
embedded mica caps built into the bottom base of the xfmr. Does this
also happen with discrete mica caps in the IF xfmrs like in this rcvr?
Any other ideas on possible causes? Thanks for the help. Mike KF6KXG

Start pulling tubes in the IF strip until you find the stage where the
noise is coming from.

Yes, the discrete mica caps can also exhibit similar breakdown. Once
you identify the stage, you can disconnect them and see if the problem
goes away.

Some resistor failures can seem similar, but they are usually combined with
microphonics as well. Not always, though.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Nov 2, 7:04*am, (Scott Dorsey) wrote:
In article ,

tchrme wrote:
I need some of the wisdom of the group. I started to have the
thunderstorm crash type of noise on all freq on my SX 100. I know this
is indicative of silver mica disease in the IF's when they have the
embedded mica caps built into the bottom base of the xfmr. Does this
also happen with discrete mica caps in the IF xfmrs like in this rcvr?
Any other ideas on possible causes? Thanks for the help. Mike KF6KXG

Start pulling tubes in the IF strip until you find the stage where the
noise is coming from. *

Yes, the discrete mica caps can also exhibit similar breakdown. *Once
you identify the stage, you can disconnect them and see if the problem
goes away.

Some resistor failures can seem similar, but they are usually combined with
microphonics as well. *Not always, though. *
--scott
--
"C'est un Nagra. *C'est suisse, et tres, tres precis."

Scott,
Thank you for the information. I will check for noisy resistors
too. Mike KF6KXG

If you look at the capacitor inside the IF can, the primary and the
secondary has very little insulation or separation between the primary to
secondary capacitor plates. There is a great DC potential from the plate
connected primary to the grid connected secondary. The potential is higher
in your Hallicrafters than the usual AA5. That is where the silver
migration or contamination occurs (from primary to secondary). Some times
scraping the migrated silver or tarnish off will solve the problem. But I
bet it would be only temporary.

I have fixed plenty of these "Thunder storm in a can" problems.

http://www.radiomuseum.org/forum/if_...er_repair.html
http://www.ppinyot.com/if_transformers.htm

And as others have said, discrete component failure (non IF cans) can cause
this symptom as well.

Good Luck,
Paul P.