[Hallicrafters] Black Beauty capacitors Beware

Sun Mar 8 14:29:21 EDT 2015

Jim,

The photos did come through.  Not that it matters since the tracking 
generator will only go down to 100KHz, but the output attenuator will 
reduce the output to -120dBm

David

On 3/8/2015 2:07 PM, Jim Liles wrote:
> Hi Dave,
>
> I sent a response with attached photos of a sweep of an SX-117 but it 
> failed.  So I resent the narrative and will add the photos to the 
> K9AXN web site.
>
> First off Dave, I don’t see anything in the mix that will reach down 
> to 50Kc.  Help me out on that one.  Haven’t used that gear for years 
> and years.
>
> I don't see anything in the mix that can do a sweep except maybe the 
> 8443A and 141T but I don’t think they make it down to 50Kc.
>
> I believe the output of the tracking generator is a bit high for the 
> I.F.Sweep so will probably need an attenuator.  You need to get down 
> to the millivolt levels for I.F. and microvolt levels for the front 
> end sweeps. What is its minimum output.
>
> Been a long time since I used a 141T but as I recall it has a storage 
> CRT standard.  Does the storage function in your 141 work and are you 
> familiar with its use?  If the storage function works, you can do a 
> single manual sweep by simply turning the frequency knob on the SG 
> letting the 141 store the trace.
>
> I have to admit I’ve never used a tracking generator, never needed to 
> do so. Most Spectrum analyzers have storage CRT or max hold 
> functions.  What’s the difference?  About 30 seconds of your time and 
> you can inject a precision signal of any amplitude, composition, or 
> purity.
>
> Let us know if the storage function works and if you’re familiar with 
> it’s use.
>
> The attached photos are of the SX-117 band pass .5Kc and 2.5Kc 
> settings. The 2.5Kc wave form looks to be only slightly wider than the 
> .5Kc because we doubled the sweep rate compressing the image. We used 
> an HP 3325A which uses a TTL transition for a matker.  The down 
> transition is the 50Kc point.
>
> The .5Kc trace is 250 cycles per graticule and the 2.5Kc trace is .5Kc 
> per graticule.
>
> Kindest regards Jim K9AXN
>
>
>
>
> -----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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>> -- 
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>> 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

-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2015.0.5751 / Virus Database: 4299/9253 - Release Date: 03/08/15