SP600-JX21 s/n 19487  as arrived, 11/17/02

panel1.jpg (33503 bytes) wpeD.jpg (35510 bytes)  top9.JPG (63919 bytes) top6.JPG (59263 bytes)

top4r.jpg (168088 bytes) rear1.JPG (58986 bytes) rear2.JPG (60151 bytes) bottom1.JPG (77551 bytes) bottom2.JPG (77500 bytes)

bottom3.JPG (75651 bytes)  pix taken Dec.02,'02  (click on thumbnails for full size, panel pix aren't very good)

Initial observations:

  1. GE Aerospace Electronic Dept tag, Engr. no. 15445, on panel, to be saved
  2. has 3-wire 120VAC cord
  3. all knobs present and in good condition, no chips noted
  4. panel paint - no bad chips or scratches exc. at rack mount screws, & some scuffs & verysmall rust spots along bottom edge.  Lettering is yellowed, not bad nicotine appearance on lettering or general panel paint.
  5. Dials clean and white, look good.
  6. Turret top & bottom covers present
  7. Spare fuse cover present but cracked & small pc missing
  8. Very dusty on top of chassis & topside components, doesn't appear to have much corrosion.
  9. Coax antenna cable, UHF to BNC with 2 adapters to get to UHF male.
  10. 3 allen wrenches in clips
  11. All tube shields present, no hold-downs for 5R4GBY (not ceramic base) or 6V6.
  12. 6 crystals in FCU, will ck frequencies.
  13. no hole plugs for L-31 & L-32 in pod.
  14. Round filter chokes in octagonal holes
  15. There are no BBOD's, this is one that got disc ceramics at the factory
  16. Audio transformer added under chassis for 8 ohm speaker output.
  17. a small 7-terminal strip near audio xfmr with several wires hanging un-connected, a coax going to AF Gain ctrl on front panel, and a small "8-legged" can connected to strip.SP600s1.jpg (39451 bytes)
  18. Took ESR readings on the 3 section (3x20mf@450v) filter cap, all at or below 1.5 ohms, which is good.  (>3 would be suspect.)


  1. Changed AC line input to the 130v tap on the power transformer (from the 117 tap).  This will reduce the voltages in the receiver, but will bring them close to, but slightly lower than, rated voltages.  Most household AC lines are above 120v nowadays, as much as 125 vac, so on the 117v tap it would be getting higher than rated voltages.
  2. Noted that the BFO only comes on intermittently, and the meter does not indicate RF level, tho' it is OK on AF.  AVC does appear to be operating, so the RF meter isn't seeing AVC voltage.  Both the BFO switch and AVC/MAN switch had intermittent sections, after a shot of MCL in each they both work OK.  Meter reads RF level OK now.  (did same in all toggle switches)
  3. Checked the AVC bias voltages, both correct at -51 & -10v, and controlling.
  4. Checked operation on all bands, no problems noted after above fixes.  Good sensitivity on all bands, Listened to the SW BC bands, heard CB signals at 27-28mc, dial calibration seemed close on all bands (WWV found right at 15mc).  There may be an intermittent contact in the turret on the lowest band (AMBC), lost sensitivity twice, but OK after wiggling band-change.
  5. I'm always impressed with the SP-600, I can usually hear an AM BC station at every 10kc point, no exception with this one, even in the afternoon.  Lots to listen to in the evening.
  6. The "8-legged" noted in #17 above is a DPDT relay.  Will try to trace out what the connections go to  & what was to operate it.  There are several wires that are hanging loose.  Did receive a sketch of the area below T-2, will check out any mods in that area.


  1.   No mods have been made in the T-2 area, inside or out.  Removed all knobs, tube shields & tubes, cleaned chassis, topsides, panel, etc.  Soaking knobs prior to clean & wax., will soak & clean shields.  Probably will remove dial bezels and repaint (overspray after wetsanding & priming).  (after closer look, they may not need it)  Will remove all IF xfmr cans & clean better, separately.  (done b4 some pix)
  2. Placed complete unit in "oven" to dry after rinsing with distilled water.
  3. This is the cleanest SP-600 chassis I have ever worked on, the RF deck top is shiny, none of the usual tarnishing on the steel.  This will be a pretty radio when done.  Panel is very good, not too much nicotine, cleaned well with only soap & water.  Lettering a little yellow, no nicks or scrapes exc. at rack mt screws, as noted before.  Will get to some detail work on it later.
panel1r.JPG (56393 bytes) under1r.JPG (60446 bytes) panel2r.JPG (49156 bytes) panel3r.JPG (51369 bytes) top1rr.jpg (193393 bytes) 

top3r.JPG (67742 bytes) top5r.JPG (67346 bytes) top6r.JPG (65048 bytes) panel2r.JPG (48403 bytes) panel4r.JPG (43984 bytes) top7r.JPG (60983 bytes) top8r.JPG (65806 bytes) 

sorry the pix are so dark.  ham fotog.  I may lighten some of the better ones, later.  or will take better ones inside, but hard to avoid flash flare .

bezel1.JPG (47914 bytes)    bezel4.JPG (44145 bytes)
left bezel, before & after touchup


Knobs and front panel have been cleaned and waxed, chassis corners, nooks & crannies cleaned, as have coil covers.
It looks clean enough, it's time to start back together.  Still have work to do under the chassis, but let's see if it still works.

ready to go top10.JPG (88253 bytes)          all in place exc. the turret cover top11.JPG (81236 bytes)

    It actually started going back together yesterday PM.  I tested tubes, 1 6C4 oscillator is bad, the 12AU7 is low but usable, the 6AC7 on the FCU, "extra" xtal osc., chassis showed a fil-plate short, I hoped it didn't cause a problem in the osc. ckt, I wasn't planning on pulling it off & apart, and planned to ck resistances at the tube socket.  But today I rechecked the 6AC7 when I was testing another as a replacement, and it doesn't show the short.  I had double ckd settings on the tester, don't know what happened.  I used DeOxit on the pins of all tubes as they went back in.

It's together, still works.  WWV still there at 10 & 20mc, SSB signals copyable on 15m.  The FCU is working with the original tube.  I did make a chart of frequencies of the 6 crystals that were in the sockets.  (non are particularly meaningful to me.) 

   frontoa2rr.jpg (230910 bytes)

I think that mod on the terminal strip at the rear, with the little relay, is something to switch from getting audio output on the speaker terminals (normally) to output on the diode load terminals for an external audio amp.  But it's got so many wires just hanging loose, I can't be sure. Will have to re-route 1 or 2 wires when I remove it, 'cuz they're going thru normally closed contacts now.


    It's very stable.  I've had it on a few times for several hours since getting it back together, and after a short warmup period, it stays right on the 14.300 Maritime Mobile Net freq. (SSB) with very little attention for an hour or more.  I removed the small mod. with the relay on the terminal strip under the chassis.  It had only 4 wires connected, and apparently would remove audio, and all AVC, when activated.  I don't know it's purpose.  I connected a tube type hi-fi amp. to the Diode Output terminal, and get great audio from the local AM station playing jazz.
    Next I will remove the small audio transformer that give 8 ohm speaker output (and no 600 ohm output), clean & DeOxit all terminals in the turret, and perform a complete alignment.


    Remove audio transformer, clean all (120) turret pins with 400 paper & DeOxit, align 455 & 3955kc IF's  start RF alignment


    Complete RF alignment, make chart of several bands' tracking accuracy.  End points are right on, but some mid-points are off by 2 or 3 widths of the pointer, not a lot, but WWV isn't right on 10mc.  9mc & 13mc are right on.  AMBC band seems right on, I hear a stn at every 10kc point.  

the number "hi" is no. of pointer widths.


Log setting

  Frequency Log setting
3.700 057.8 ok   10.000 235.5  2 hi
4.500 189.5 ok   11.000 315.5  2 hi
5.500 338.4   2 hi   12.000 391.0  1 hi
6.500 470.2 ok   13.000 462.7 ok
7.200 557.2 ok   14.000 631.8 ok
7.255 563.5 ok   15.000  xxx  1 lo
8.000 063.8 ok   20.000 227.2  3 hi
9.000 150.8 ok   24.000 384.5  4 hi

Removed line cord & bypass caps in preparation for installing strain relief & new bypasses.  Line cord insulation is badly cracked and it will be replaced.  (there was no strain relief, the cord just went thru a hole in the chassis.


ACin2.JPG (64417 bytes)

    Enlarge hole for strain relief, install it & 2 new surge protection/bypass caps.  Rewire AC input wiring to run the hot line thru the fuse and to the on/off switch, and put the neutral line to the transformer primary.  Bypass caps are - 1 across the line, and 1 from neutral to ground, which I understand to be the proper configuration.  Install new stainless steel fasteners, w/washers, to hold the panel to the chassis.  

frtdone1.JPG (60429 bytes) frtdone2.JPG (53559 bytes) frtdone3.JPG (53409 bytes)

After I mix up and apply better matching touch-up paint, this unit will be complete.


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