SP-600-JX-17, #10354

(Click for full-size picture)	This is an SP-600-JX17, serial number 10354. 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 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. The frequency and vernier dials were quite clear on this unit, so I did not replace them with dial overlays. I did clean them up a bit. Note that in the process of restoration, I completely disassemble the receiver - I take all the gears off on the front panel and remove all the major assemblies (that come off, that is). 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. This radio had been recapped by some previous owner. The recapping job was pretty well done, so I felt no need to redo it. I did check and replace a number of capacitors and many resistors and a number of wires.
(Click for full-size picture)	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 was relatively 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. This unit has four outputs on the back. Only three are described in the manual. The fourth is quite common in the JX17, although it was probably installed after it left the factory. It is an output for a panoramic adaptor, such as the Panadaptor PCA-2 or the Hallicrafters SP-44. This output comes right out of the second mixer/gate output and right before the 1st IF stage. All the miniature tubes have the IERC heat-sheding shields or their Cinch equivalents. These are the only tube shields known to actually increase tube life.
(Click for full-size picture)	This unit had already been recapped, so all I did was check the resistances and the connections and replace the odd part or wire that looked suspicious. I replaced the first RF tube with a 6BZ6 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). I did check the oscillator output plug on the back, and I did try tuning the receiver by supplying a signal through the connector on the back of the FCU. I had to replace T35. This has been broken and useless on every single JX17 receiver I have ever worked on. I rewind the auto-transformer on a new toroid and seal it in epoxy before installing it. I use a high-frequency material for the toroid that responds easily to 40 MHz and beyond. Although I don't expect anyone to actually try to use the receiver in diversity mode, I did check all the inputs and outputs necessary to make that mode work. I personally feel that the original design is not very good when using the VFO from one receiver to drive the other. The output voltage is not very high, and is even less by the time you get all the way into the slave receiver. It actually works a lot better to drive two receivers from a modern signal generator. That works quite well.
(Click for full-size picture)	This shows the recapping job on the IF and AF sections. Although the unit had been previously recapped, some of the capacitors did need replacing. 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.
(Click for full-size picture)	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.
(Click for full-size picture)	All the wires going to the right side of the front panel were disintegrating. The insulation had peeled off and there were just bare wires going this way and that. I replaced them all and connected them to the cable once they got inside the chassis.
(Click for full-size picture)	Oops! While tightening the panel screw, I slipped and put a big, nasty scratch in the front panel. I did respray it, but it never looks quite as good as new again. Oh well.