[Hammarlund] Hammarlund SP-600

[Richard Knoppow]

----- Original Message ----- 
From: "Tom Lewis" <n4tl2 at yahoo.com>
To: <hammarlund at mailman.qth.net>
Sent: Sunday, April 22, 2012 8:43 AM
Subject: [Hammarlund] Hammarlund SP-600


Hello,

I need some help with a SP-600 JX-26 (SN 13432) that I 
purchased at the Richmond VA hamfest back in February.

I have replaced all the electrolytic and paper capacitors. 
For the audio
output, I am using a 70 V, 15 watt line matching transformer 
that I purchased
from Parts Express. Their part number 300-039. The radio is 
working okay with the new capacitors and audio transformer.

Where can I buy a rectifier tube hold down bracket? The 
radio has the
long screw next to the tube but the bracket at the top is
missing.

I have to make or buy a
bottom cover. Does the bottom cover have any holes in it 
other then the 7 for
screws that hold it in place? Does anyone have one for
sale?

Where can I buy new caps for the 3/8 inch tuning holes?

Thanks
Tom, N4TL

     The tube hold down for the rectifier is often missing 
because it won't fit the ruggedized version of the tube 
which was the one most often used.  It simply is not 
necessary.  There are also hold downs on the 6V6 audio 
output and for the crystal oscillator tube. All unnecessary. 
I don't know of a specific source.
     The plugs for the tuning holes are standard hardware 
items sold as goof-plugs, hole plugs, other names, a good 
hardware store will have them.  Not expensive items.
     You will have to make a bottom cover.  They were 
supplied on the rack mount version of the receiver but not 
the cabinet version.  You can tell which you have by the 
back corner brackets, for the rack mount receivers they are 
about 1/8th inch below the edge of the chassis, same as the 
others, for the cabinet version they are flush. If you have 
the cabinet version you will have to make new brackets. 
Actually, I think you can use the existing ones by drilling 
new holes in them so that you can mount them in the correct 
position.  When the receivers were new a kit was available 
for conversion of one type to the other.  The bottom cover 
is just a sheet of metal with holes punched for the 
retaining screws.  The screws are 10-32 binding head screws. 
There are no other holes.
     Rack mount receivers also had top covers.  These are 
illustrated (badly) in some of the service manuals.  Its a 
sheet of metal with brackets at the corners for knurled 
thumb screws and a rubber gasket across the front. The main 
purpose was to prevent things from falling into the dial 
gears.  I think the bottom cover is a good idea since it 
will provide some additional shielding but the top cover is 
not necessary.
     The Allen wrenches which were attached to the fahnstock 
clips on the side of the tuning unit are standard hardware 
items.  New crystal hold down springs are available from 
James Moorer, he sells them via eBay.  I think he also sells 
replacement covers for the spare fuses on the back.
     A great deal of information exists on the web. A 
warning!  One web site advises bending the plates of the 
main tuning capacitor to adjust it NEVER do this, it will 
ruin the capacitor.  Sometimes the tuning capacitors get out 
of alignment. The alignment can be restored by adjusting the 
centering of the stators in the rotors. That will usually 
restore correct operation. You never have to bend plates 
and, if they have been bent, you will not be able to get the 
calibration and tracking properly adjusted.
     If your receiver still has the original Black Beauty 
capacitors in it they should be replaced en-mass with new 
NPO type ceramic caps.  A lot of work because there are a 
lot of caps, but mostly not difficult to do.  Many of these 
receivers were modified by the military to replace the caps 
since the BB's began to go bad within a few years of being 
manufactured.  I have also had occasional difficulty with 
unstable silvered mica caps, particularly the 51pf ones in 
the BFO and 4mhz IF can. Its also important that the dials 
be properly aligned.  I will post a method I found works if 
you like. The main pointer should run straight up and down 
and the zero indication of both logging dials should match. 
If the pointer runs at an angle it will make it impossible 
to get good calibration on all bands.
     These are very good receivers and are worth some effort 
to make right.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com