SP-600-JX-17, #14956

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This is an SP-600-JX17, serial number 14956. 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. I applied dial overlays to both the frequency and the vernier dials (originals on the back). I also had to overlay the band readout dial. Large hunks of paint had flaked off.

I will warn you that the unit, in person, doesn't look as good as these pictures look. I don't quite know why, but the pictures look great, whereas the actual unit has some nicks and scrapes and rust spots on the chassis. I replaced a lot (not all) of the hardware with stanless - especially on the front panel. Every time I took a screw out, I replaced it with stainless, and every time there was a markedly rusty nut or screw that I could get to, I replaced it.

All the controls on this unit operate smoothly and without problem. The BFO select rotary switch disintegrated when I took it apart. I replaced it with one with ceramic wafers instead of bakelite. One curious side-effect is that all I had was a 5-position switch instead of the original 4-position switch, so there is an extra "hidden" setting. I wired it to be the same as the first position, so there is no additional functionality.

The skirt of the AF gain knob has a sorta white wash on it that I couldn't clean off. You can see it is a bit whiter on the front panel picture. Sorry. There is also one red knob that is a bit funky - it didn't clean up really well. I did go through and replace all the set screws in the knobs with stainless. Maybe they won't freeze up like the originals did..

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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.

This one came with two of those cool original red plastic covers for the back panel connectors. They are hard and stiff and don't come off easily, but they look neat. I wish I had some more of them.

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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.

Sorry about the two-toned power transformer. I was worried about the rust spots, so I sanded them down to bare metal then hit it with some rust-o-leum. Of course, the paint was a different shade, so we have a two-tone transformer.