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This is an SP-600-JX17, serial number unknown (maybe 11000 or so?). It was made for
the Air Material Command. This is the "diversity" receiver.
I did refinish the front panel.
I used a darker grey so the engraving and the dials stand out better. I did repaint
the black knobs knobs on this one (not the red ones). They were quite dull.
I did not try to repaint the meter. I
was worried that some paint would get into the mechanism. This one
has the original dials on both the frequency indicator and the vernier.
They were in good shape and did not need dial overlays.
All the controls on this unit operate smoothly and without problem. I replaced
the AGC/MAN switch with one of modern manufacture.
Hmm. I just noticed that the RF gain knob was off in two of these pictures. Sorry about that.
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I did wash and scrub the sheet metal with a scrubby sponge. No steel wool was used in the process.
De-Oxit was applied to all the tube sockets. The chassis did not need any work - it
wasrelatively clean and square. It was apparent that this receiver had not been dropped or
otherwise mishandled. There were no bent edges or crushed corners.
I replaced the missing tube hold-down clips
on V3, and V17.
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This is where I spent most of my time: the RF deck. All the caps were replaced with 600V
ceramic. A number of resistors were replaced as well. I used a lot of shrink-tubing on the
leads to prevent shorts but still allow you to get a tool in to align it. A number of wires
were replaced. Several out-of-spec resistors were replaced.
The caps were dressed to hug the ground plane wherever possible. I replaced the first RF
tube with a 6JH6 for added sensitivity.
You notice that the FCU (the crystal oscillator) has the 6AH6 tube on this model (as opposed
to the 6AC7 on other models).
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This shows the recapping job on the IF and AF sections. All the orange items are 600V SBE
(née Sprague) "Orange-Drop" 716P capacitors. A number of resistors had to be replaced
in this area as well. Several capacitors were bad and were replaced. Most of
the high-resistance (500K and greater) resistors were wildly out-of-spec and were replaced.
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This is the rebuilt power section. I replaced the electrolytic with 47-uf, 450-V special high-ripple
tolerant, long-life, electrolytics. You should be able to pass this one down to your
grand-children.
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All the miniature tubes have the IERC heat-sheding shields. These are the only tube
shields known to actually increase tube life.
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