[Hammarlund] Part # of Hammond chokes /recapping questions for SP-600

[Singley, Rodger]

Some of the SP-600 receivers were built with chokes that apparently have contaminated potting tar which becomes conductive over time.  I am one of the "lucky" owners of one of the afflicted units.  With the leads disconnected you will measure leakage from the terminals to the case and this leakage goes up with temperature.  I considered insulating mine from ground but I really don't like (for safety reasons) to float components above ground that everyone expects to be grounded.

It has been 8 years since I went through mine and I am pretty sure I used Hammond replacements which fit OK.  My SP-600 is mounted in a rack with some other heavy gear so it isn't readily accessible for me to check the part numbers I used.

My advice is to measure yours to see if they are leaking before you worry.  I don't think the number of these with the problem chokes is that large but I had read about others experiencing that problem before I started on mine and sure enough I won the leaky choke lottery.

If yours are leaky, you should replace them as sooner or later they will probably have a hard failure and they will cause excessive current draw through the power transformer in the meantime.

On a happier Hammarlund note, I just wound a set of coils for my Comet Pro to cover the 80 meter band and since I didn't have DSC wire I substituted modern enameled wire.  I had to remove one turn each from the oscillator and input coil to get them to agree with the dial calibration.  This is a pretty impressive receiver for being such an early (1932) superhet.  No bad chokes or transformers either :)

Rodger WQ9E


-----Original Message-----
From: hammarlund-bounces at mailman.qth.net on behalf of Al Parker
Sent: Tue 3/9/2010 6:07 PM
To: jdkopke at cablespeed.com
Cc: hammarlund at mailman.qth.net
Subject: Re: [Hammarlund] Part # of Hammond chokes /recapping questions for SP-600
 
Hi John,
     Carl's right on the caps.  Even the factory changed over to all 
ceramic discs after abt ser. no. 17,500.
     The p.s. filter cap is the only big electrolytic in there.  Tom's, 
at Hayseed, is a good replacement.  Sorry, I don't know of a particular 
direct replacement for the chokes.  Do you suspect a problem with 
yours?  They do fail, but rarely.
73,
Al, W8UT
New Bern, NC
www.boatanchors.org
www.hammarlund.info

"there is nothing -absolutely nothing- half as much worth doing as  
simply messing about in boats."
   Ratty, to Mole



On 3/9/2010 2:54 PM, John D. Kopke wrote:
> Hello all, I understand there's a replacement part that's close to original for the
> chokes in the power supply of the SP-600 and was wondering what those were in the
> event I have to replace them .It's an early sp-600 (jx-1 ).I have found a antique
> radio repairman in my area. The catch is, he's not familiar with Hammarlunds at
> all.I also have a new filter cap from hayseed on the way. Is that the only large
> electrolytic can I need to replace ? Also some tell me to go with orange drops and
> others tell me ceramic disc's. I'm not sure what to get . Many thanks
>
>
>
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