[Hallicrafters] Hallicrafters SX-71

Thu Feb 14 23:51:52 EST 2008

Hi Bill,

The 71 is a favourite of mine. I currently have two, and sold a third a 
while back.
(Nobody needs three SX71s!)

I put some info here that you may find useful:
http://pcbunn.cacr.caltech.edu/jjb/Hallicrafters/SX71/sx71.htm

I had some good fun aligning with sweeps:
http://pcbunn.cacr.caltech.edu/jjb/Hammarlund/if_alignment.htm

(for a Hammarlund, but I used the same method for my Hallis, including 
the SX71).

Best wishes,
Julian

Bill Collins wrote:
> It's good to see some reference made to the sx-71.  I have two that I have 
> been working on for a while.  The first one I bought from an estate of an 
> SK, and he had been working on the 2nd converter--I had no idea of what he 
> had actually done or why, so started looking for a parts rig, found one at a 
> hamfest, took it home and it actually worked a little.  Well, My parts rig 
> changed into a "let's fix this one too" rig.  I rebuilt the 2nd converter 
> assembly, found a couple of resistors burnt in two, replaced them, recapped 
> both radios, and now that I have gone back to work (after 5 months of 
> disability), I don't have time to pursue them anymore (I need to retire, 
> no?)  I am pretty sure that all they need now is just realignment, so I am 
> looking forward to that, but don't have any experience doing such.  I have 
> an old but stable Heathkit signal generator (recapped and checked, tools, 
> manual, a sams photofact, and no time.  Dang it.  So one of these days,  I 
> will be whining for help on this project.  I really enjoy all the info 
> provided by the members-lots of good reading, and I even absorb some of it! 
> haha.  If anyone has any tips or pointers on the SX-71,   I will be all 
> ears.  I took lots of digital pictures along the way while I was operating 
> on the 2nd converter especially.
> Anyway, thanks for the info  that you all share.
> Bill
> N zero R R and a Y
>
>
> ----- Original Message ----- 
> From: <hallicrafters-request at mailman.qth.net>
> To: <hallicrafters at mailman.qth.net>
> Sent: Thursday, February 14, 2008 3:00 AM
> Subject: Hallicrafters Digest, Vol 49, Issue 20
>
>
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> Today's Topics:
>
>    1. (no subject) (Bill)
>    2. SX-71 serial # and Run # markings (Chuck McGregor)
>    3. Re: Re: [Boatanchors] Replacing recttubeswithdiodesquestion
>       (jeremy-ca)
>    4. Re: SX-71 serial # and Run # markings (W4AWM at aol.com)
>    5. Re: Replacing 6H6 with diodes. (Kenneth G. Gordon)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 13 Feb 2008 19:53:32 -0500
> From: "Bill" <kirklandb at sympatico.ca>
> Subject: [Hallicrafters] (no subject)
> To: <hallicrafters at mailman.qth.net>
> Message-ID: <002201c86ea4$09b1d380$1401a8c0 at bill1qh4y921ze>
> Content-Type: text/plain; charset="us-ascii"
>
> Yes, I am in a pissy mode. My humble apologies.
> I meant to ask to ask for the previous email to be passed along.
>
> Now to the basement with a beer.
>
>
>
> ------------------------------
>
> Message: 2
> Date: Wed, 13 Feb 2008 17:59:26 -0800
> From: Chuck McGregor <cbmcg at comcast.net>
> Subject: [Hallicrafters] SX-71 serial # and Run # markings
> To: hallicrafters at mailman.qth.net
> Message-ID: <20080214020553.EC50F8582AD at mailman.qth.net>
> Content-Type: text/plain; charset="us-ascii"; format=flowed
>
> Sorry to ask a seemingly silly question, but where should I expect to
> find the serial number and the run number stamp on an
> SX-71  ?   They're not on the chassis top or the rear apron, and
> there's nothing on the inside of the chassis side panels (where the
> SX-42 run # hides).  I find three inspection stamps on the chassis
> underside, below the 2nd converter subchassis.  I haven't pulled the
> front panel to see if any numbers are hidden behind it.
>
> Thanks & 73
> Chuck N7RHU
>
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 13 Feb 2008 22:17:22 -0500
> From: "jeremy-ca" <km1h at jeremy.mv.com>
> Subject: Re: [Hallicrafters] Re: [Boatanchors] Replacing
> recttubeswithdiodesquestion
> To: "Bill" <kirklandb at sympatico.ca>
> Cc: boatanchors at mailman.qth.net, hallicrafters at mailman.qth.net
> Message-ID: <02f201c86eb8$1f4ff230$6500a8c0 at KITTYMA123>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
> Bill, it took me quite awhile to quit laughing, you should do well in a
> stand up comedy club!
>
> Engineering tradeoffs, phase noise, IP3 and AC/DC all in the same breath! On
> a 60-70 year old entry level radio no less which was the start of this
> thread! I could see it if the SX-115 was being discussed but a S-40B? Wow,
> what a stretch!
>
> If you wish to discuss those engineering performance subjects and my
> involvement with Ulrich Rhode, Kenwood and Yaesu I will be glad to discuss
> it on the proper forum. The Hallicrafters or Boatanchors forum is not the
> place for it.
>
> Carl
> KM1H
>
>
>
>
> ----- Original Message ----- 
> From: "Bill" <kirklandb at sympatico.ca>
> To: "'jeremy-ca'" <km1h at jeremy.mv.com>; <wq9e at dtnspeed.net>;
> <erastber at tampabay.rr.com>
> Cc: <boatanchors at mailman.qth.net>; <hallicrafters at mailman.qth.net>
> Sent: Wednesday, February 13, 2008 6:52 PM
> Subject: RE: [Hallicrafters] Re: [Boatanchors] Replacing
> recttubeswithdiodesquestion
>
>
>   
>> Unfortunately Carl I don't seem to have a copy of an earlier email from
>> you
>> discussing any exceptions or voltage reduction.  I only saw the email I
>> responsed to
>> which made quite blunt general statements.  What I've found lacking in
>> your responses
>> Carl is a lack of discussion of the engineering trade offs or a good
>> solid analytical
>> analysis. Please pass it along.
>>
>> e.g. Just because something is done, in one receiver, e.g. AC/DC radios
>> where
>> B+ is applied, doesn't mean it was the best thing to do. They may well
>> have made an engineering trade off, cost, performance, simplicity of
>> design for the
>> sake of some tube life. Who knows, maybe it was intentional, keeps the
>> customer buying
>> tubes.
>>
>> As for National giving the ok, great but since I don't have access to
>> the engineering
>> report I have no idea what the trade offs are.
>>
>> As for receiver sensitivity, good to hear that it didn't change but what
>> other parameters
>> have to measured, e.g. IP3, oscillator phase noise?
>>
>> Instead of indicating such and such is a myth because "it worked for
>> me/others", I would
>> rather see a good solid engineering/analytical discussion.
>>
>> It's good to have a great RF lab, unfortunately you didn't quote any
>> measured results.
>> Maybe in a previous email thread? If not, posting them and maybe some
>> enterprising
>> individual could put it up in an html page. Reminds me, guess I should
>> do a google.
>>
>> I merely pointed out the obvious differences between the tube rectifier
>> and the solid
>> state rectifier.  If you have some good analytical data, I would love to
>> see it and then
>> perhaps a good html page could be set up.
>>
>> I guess in summary there are 4 groups, "best practices", "acceptable
>> practices", "bad practices"
>> and anything else.  It seems some of those that methods that might be
>> considered "best (better)practices"
>> get relegated to myth status.
>>
>>
>>     
>
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 13 Feb 2008 23:34:10 EST
> From: W4AWM at aol.com
> Subject: Re: [Hallicrafters] SX-71 serial # and Run # markings
> To: cbmcg at comcast.net
> Cc: hallicrafters at mailman.qth.net
> Message-ID: <cef.2a1d7fce.34e51ec2 at aol.com>
> Content-Type: text/plain; charset="US-ASCII"
>
> Hi Chuck,
>
> The serial numbers on most Hallicrafters receivers of that vintage were on
> paper tags glud to the rear chassis banel. Unfortunately, many have not 
> passed
> the test of time and rough handling. Normally the run numbers are stamped on
> top of the chassis. If you don't see the run number, I could consider it to 
> be a
> first series.
>
> 73,
>
> John,  W4AWM
>
>
> **************
> The year's hottest artists on the red carpet at the
> Grammy Awards. Go to AOL Music.
>
> (http://music.aol.com/grammys?NCID=aolcmp00300000002565)
>
>
> ------------------------------
>
> Message: 5
> Date: Wed, 13 Feb 2008 22:59:11 -0800
> From: "Kenneth G. Gordon" <kgordon2006 at verizon.net>
> Subject: [Hallicrafters] Re: Replacing 6H6 with diodes.
> To: Hallicrafters at mailman.qth.net
> Message-ID: <47B3763F.31712.DCB085 at localhost>
> Content-Type: text/plain; charset=US-ASCII
>
> On 14 Feb 2008 at 9:59, Rodney Bunt wrote:
>
>   
>> Not only high back resistance you need VERY low forward junction
>> voltage. A tube diode conducts in the forward direction from a VERY
>> low voltage. A diode if silicon needs approx 0.7v forward bias before
>> it conducts, a Germanium (1N34) needs 0.3volt forward bias. Today you
>> could use Shotkey diodes, but the 6H6 uses very little power and works
>> very well.
>>     
>
> Yes.
>
>   
>> An old trick is to reduce the filament voltage, thereby
>> reducing the "electron cloud" around the cathode (these -ve electrons
>> tend to repel other electrons from leaving the cathode) reducing the
>> filament voltage, reduces the "cloud" reducing the forward bias
>> voltage necessary to conduct.
>>
>> Rodney
>> VK2KTZ
>>     
>
> Thanks for the tip, Rodney. And you're absolutely correct. I
> can't see any good reason to change a 6H6 for a pair of SS
> diodes. The SS diodes won't do as good a job, and there
> really isn't much of a savings. The 6H6 is very reliable.
>
> When I changed the 6H6 in my Scott SLR-F back in the
> 1960s, it REALLY didn't help. In fact, the change made it
> work worse. I took it out.
>
> Thanks for the info.
>
> Ken Gordon W7EKB
>
>
> ------------------------------
>
> ______________________________________________________________
>
>
> End of Hallicrafters Digest, Vol 49, Issue 20
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