[Boatanchors] IF transformers

[Carl]

The problem has been called by many as SMD (Silver Mica Disease) and has 
become a huge problem with 1951 and later IF's that use slug tuned coils. 
Its getting worse as time goes on and the silver continues to migrate.

Values generally run from 82 to 130pf  (using standard value dipped micas) 
for 455kHz. Pick a number in the middle and see which way the slug moves to 
at least start increasing the signal. All the way out means less C, dead 
center means more is needed.

I think I have a problem starting in a HQ-180 and have repaired around 20+ 
regular consumer grade radios the past few years.

Carl
KM1H

----- Original Message ----- 
From: "Drew P." <drewrailleur807 at yahoo.com>
To: <boatanchors at mailman.qth.net>
Sent: Sunday, February 14, 2010 4:39 PM
Subject: Re: [Boatanchors] IF transformers



Patrick wrote:

> I've repaired one IF can in a HQ-170 this way. The
> cap inside the IF  can had shorted and took out a
> small resistor. I went slow and took digital photos.
> The photos are really worth the time when the work is
> spread out over an evening or two. If you don't have a
> camera with a good close up lens pencil on paper
> stretching works okay too.
>
> I ending up mounting the replacement cap just under
> and outside the IF coil because I couldn't determine
> what value was needed. I tacked different values in
> place until one tuned okay.
>
> It would have been a big help to know the correct
> replacement value prior to dis-assembly. I never
> found where that was published.

[snip]

So, at what value did you arrive?  The suspense is killing me!

Drew




______________________________________________________________
Boatanchors mailing list
Home: http://mailman.qth.net/mailman/listinfo/boatanchors
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Boatanchors at mailman.qth.net

List Administrator: Duane Fischer, W8DBF
** For Assistance: dfischer at usol.com **


This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html