SP-600 s/n 4610,  R-274A s/n 1639

Received 9/3/05

b4frtoa1.jpg (189002 bytes) b4topoa.jpg (213535 bytes) b4top2.jpg (185116 bytes) b4rlftamps.jpg (185245 bytes) b4rtlamps.jpg (208040 bytes) b4lftspnl.jpg (164185 bytes) b4rtspnl.jpg (153965 bytes) b4pnltopl2.jpg (180417 bytes) b4pnltopr.jpg (169285 bytes) b4pnlbotl2.jpg (171677 bytes) b4pnlbotl3.jpg (235031 bytes) b4botoa1.jpg (301489 bytes) b4botrt1.jpg (278440 bytes) b4botrl.jpg (285423 bytes)

General Observations:  This receiver is in generally good condition, from first (and subsequent) observations, although it is generally dirty.  It has top and bottom turret covers, no "dust" covers.  All tubes except the 6AC7 in the FCU are in place.  1 7-pin tube shield (OA2) is missing, one has been replaced by an "off-brand" heat dissipating shield.  There is no hold-down clamp for the 5R4 rectifier, others are in place.  It's is missing 2 hole plugs in the RF deck "pod".  The chassis top is etched and/or pitted over much of its' surface.  The RF deck top surface is very pitted/tarnished.  IF cans will clean up well if buffed.  It may have had a top dust cover at some time in the past, as there is evidence of damage (fraying) to the dial lamp wires by pressure from a heavy object on top of the cover. 

    The front panel appears to have been repainted, it has orange-peel, and the dial bezels had been removed at one time, but it is in generally good condition, very little scratching or chipping.  It has a slight bend at the bottom left corner, which can be straightened.  The filled, white, lettering is poor in some areas, can be re-filled.  The dials are clean and white.  The tuning feel is good, smooth, with no slippage, and will go end to end in less that 5 flicks of the wrist.

    All visible 'black beauty" capacitors have already been replaced.  Can't tell if the RF deck pod has been, probably not, as the FCU hasn't been removed previously (and it also probably hasn't been recapped.  The RF deck has been removed, and has been recapped, tho' it can't be determined if completely (probably so).  2 hold-down clamps for the xtals on the FCU are gone.  All bathtub caps except for the AC line bypasses have been replaced with discrete capacitors, but some left in place.

    The send/receive and Mod/CW switches are non-original, they have longer handles than the normal short ones.  The Xtal Phasing knob is not correct, it is the same as the RF gain knob, not a zero center knob.

    It powers up OK, doesn't draw excessive current, receives on all bands.  Primary tap on the power transformer was changed from the 115v to the 130v tap before powering up.  The BFO freq. is way off, the Selectivity switch has dirty contacts.  Every thing seems to be working OK at first quick look, but all was not checked closely.


I have removed all covers, IF cans, tubes, etc., to get started on work. Close inspection thru the RF deck tuning holes shows that all BBOD's have been replaced, with a mixture of Orange Drop, disc, and "yellow plastic" capacitors. Some resistors have been replaced. A resistance check at all tube pins shows the RF deck to be good, and only 3 areas to be further checked, 2 at the audio output tube, which will affect biasing, and one at the dropping resistor to the voltage regulator tube. Most replacements for the BBOD capacitors are the yellow plastic ones, 0.0022mf. Replacement work quality was reasonable in most areas (but see below), some resistors have been replaced, as have the B+ filter capacitors (ESR checks good on them).  All terminal strip pins have been checked for resistance to ground, vs the chart.  Only 1 area questionable, and will be checked.

The front panel will be removed for re-painting. The side panels will be removed for cleanup and to facilitate chassis cleaning. The FCU, xtal freq. ctrl unit, will be removed and re-capped, it doesn't appear to have been done, and it is necessary to remove it to change the 2 BBOD's in the "pod" on the side of the RF deck. The hold-down straps on the power transformer and chokes are tarnished, cleanup will be done.

a previous hand has been into this receiver, some of the workmanship is less than what I try to exhibit in my work.  I've tried to clean some things up.

poor12.JPG (75236 bytes) poor14.JPG (64357 bytes) many leads aren't wrapped tightly, ends stick out and aren't soldered.

I found one instance where 2 capacitors had their ground end wrapped loosely around a wire to a ground lug, and not soldered.

     poor11.JPG (70734 bytes)                         pbetter11.JPG (57175 bytes) 

B+ filter caps - before                          a little neater

2 bathtubs were still in use, they have been removed and replaced with discrete capacitors.  The turret modules which used BBOD's have been removed and will be "expunged".  One other module, which used a small postage stamp mica in a non-frequency determining area was found to have been modified by the addition of a small capacitor in parallel with it.  They will be replaced with a dipped mica of proper value.


TurMod.JPG (59685 bytes) BBOD's removed from the 6 turret modules that contained them. Most had 1 to 4 megohm resistance at 250 vdc.  The 1 module had an added capacitor across the mica to make ~1500pf as specified.  They were replaced with a 1500pf dipped mica.  

FCU2.jpg (138123 bytes) FCU3.jpg (153088 bytes) The Freq. Ctrl Unit, FCU, after cleanup and re-cap.  It's plate dropping resistor was cracked and open, it's bypass cap, a GLOD, "Grey Lady of Deception",  measured 5meg at 500vdc when cold.

 B4cleanchokes2.jpg (111077 bytes) B4cleanchokes1.jpg (181545 bytes) Filter chokes before cleaning, may need some touch-up paint.

chokesaft.JPG (40469 bytes) Filter chokes after cleaning and touch-up, much cleaner, touch-up areas are slightly visible, paint not perfect match.

B4cleantop1.jpg (261595 bytes) Chassis with side panels removed, ready for cleaning.

  Aftcleantopfr.jpg (234582 bytes) Aftcleantoplft.jpg (233868 bytes) Aftcleantoprt.jpg (251147 bytes) after cleaning.  

The RF deck took some work, but came up nicely, maybe not quite as nice as it looks in the pic.  The flash does mask some of the pitting in some pix.

 POD.jpg (166882 bytes) "Pod" with one GLOD  cap.  This is one area that was overlooked by the previous worker.

Only a few electrical things and a little cleanup left to do before starting re-assembly - also still need to strip and re-paint the front panel.

I have re-installed the FCU, IF cans, filter chokes, filter caps and side panels after cleaning/buffing them.  It looks pretty nice, will get a pic later.  Have stripped the front panel, probably won't get it painted for a cupla days, will be away over 1 nite this weekend.  Need to re-install the dials & gear change mech., and new toggle switches.  Then once the panel is done, just electrical checkout and alignment is about all left.  

I've spent several hours on 3 days this week painting, repainting, touching up, etc., 2 panels and 1 cabinet.  I finally got this panel where I'd accept it, so baked it, then re-installed the band change mechanism, the dials, and new toggle switches to prepare for re-installation of the panel.   I also filled the lettering of the panel.  Now, tomorrow, I'll wax it when the lettering paint has dried, and get it back on.  Well, that might not be tomorrow, it looks like it might be a good day to go sailing, that takes precedence over most things.  Here's a preview:

Frtprev1.JPG (79535 bytes) FRTprev2.JPG (73113 bytes) PNLdone1.JPG (52078 bytes) PNLdone2.JPG (36864 bytes) 

I've re-installed the components on the front panel, and installed it on the chassis.  (The dial lock mechanism is incomplete inside, but was re-installed and looks normal from the outside.)  After power up and some checks I did some band cruising with it, it has very good sensitivity already, without any alignment, and the dial calibration isn't bad.  It improved even more after a full alignment, overall the alignment wasn't too far off, but there were some marked increases in sensitivity noted.  When done, in the early evening, I heard CHO, 740kc, in Toronto, better on it than on my "shop listener" SP-600, with either the wire or loop antennas.  

I decided to sweep the 455kc IF, to level the response and try to get it relatively even in amplitude on each selectivity setting.  It flattened out nicely, the 8kc position still shows less amplitude, but it is not greatly noticeable audibly.  The freq. scale is more than 1kc/division, made that way for better fit on the screen and synch stability.

IF3kc.JPG (52538 bytes)  IF6kc.JPG (54075 bytes)  IF8kc.JPG (63065 bytes) 

IF sweep traces at 3, 6, and 8kc bandwiths 

I spent a little more time cleaning up some of the work that had been done by a previous hand (not mine) that was not up to my standards.  Leads had been left long, wrapped around the outside of terminal strip lugs, and just didn't look very professional.  I did the worst looking ones that could be done easily without danger of causing more harm.   Cleaned and replaced tube shields, hole plugs and covers.  The FCU, crystal controlled freq. controller, works on both single and double conversion bands.  The Crystal Phasing circuit works, but not as well as some do.  The notch is there, but not pronounced, and doesn't move much.  The 455kc crystal may not be too active. 

It's done.  Sorry the digicam isn't higher resolution, the front panel is real sharp, as can be seen in the one close-up above.

Done3.jpg (210925 bytes) Done5.jpg (187566 bytes) Done6.jpg (218722 bytes) Done8.jpg (234467 bytes) 


Radio to home page

comments to anchor@ec.rr.com

The owner's installation when complete

SP600sn4610pix/SP600_4610ATr.jpg (157894 bytes)






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