[Hallicrafters] Black Beauty capacitors Beware

[Jim Liles]

I added photos of a sweep analysis of the .5Kc and 2.5Kc selectivity settings on the SX-117. 

 http://www.k9axn.com/_mgxroot/page_10876.html 

-----Original Message----- 
From: David C. Hallam 
Sent: Sunday, March 08, 2015 8:38 AM 
To: Jim Liles ; hallicrafters at mailman.qth.net 
Subject: Re: [Hallicrafters] Black Beauty capacitors Beware 

Jim,

TEK 465 scope
HP 606B/8708A SG
HP 410C vtvm
HP 141T/8552B/8553B SA
HP 8443A tracking generator
HP 5246L FC

I also have an old EICO 369 sweep generator but I am not sure it is 
working properly.

David

On 3/7/2015 10:06 PM, Jim Liles wrote:
> Dave,
> Tell us what equipment that you have available and we'll see what we 
> can do to configure it to make it happen.  Have you done any sweep 
> analysis?
> Kindest regards Jim K9AXN
> -----Original Message-----
> From: David C. Hallam
> Sent: Saturday, March 07, 2015 4:01 PM
> To: hallicrafters at mailman.qth.net
> Subject: Re: [Hallicrafters] Black Beauty capacitors Beware
> Jim,
> What is the recommend procedure to sweep the the filter? I do not have
> a sweep generator but do have a good assortment of test equipment.
> David
> KW4DH
> On 3/7/2015 10:20 AM, Jim Liles wrote:
> > Hi Greg,
> > good assoermentr
> > Exactly!  They were as good as film and legions better than 
> ceramic.  That’s why you still see paper defined on the schematics not 
> ceramic caps.
> >
> > I still would replace the paper because as they dry out or begin to 
> leak the Q goes to the devil.  Won’t effect the .5Kc position because 
> it doesn’t use them but when you use the higher band widths, 
> especially the 1Kc, they will widen because of the denigration of the 
> Q.  May not be obvious but if you sweep that filter system it’s 
> obvious. The band center skew jumps out at you when using the ceramic 
> caps.
> >
> > In any case the paper at their worst will out perform ceramic unless 
> they are shorted or open.
> >
> > One measure is, you should be able to tune in an SSB signal in the 
> 5Kc position and dial right down through 1Kc and still clearly copy 
> that conversation without touching the BFO and tuning to peak for 
> clarity.  The best definition that describes what you have to do when 
> incorrect caps are installed is “You have to be a human I.F. shift 
> mechanism” You have to tune an SSB signal then tune slightly back and 
> fourth for peak strength while adjusting the BFO for clarity.  You 
> don’t want to go there, let the radio do it for you.
> >
> > One thing that I didn’t mention is the 390 ohm resistor will be well 
> above 420 ohms.  Those resistors are very critical.  Get it right on 
> or 5% below not above or the 5Kc position will droop excessively.
> >
> > Kindest regards Jim K9AXN
> >
> >
> >
> >
> >
> >
> >
> >
> > -----
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> -- 
> There are two possible outcomes: if the result confirms the 
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> If the result is contrary to the hypothesis, then you've made a discovery.
> Enrico Fermi
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-- 
There are two possible outcomes: if the result confirms the hypothesis, then you've made a measurement.
If the result is contrary to the hypothesis, then you've made a discovery.
Enrico Fermi




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