"Nelson" wrote in message
...
"Richard Knoppow" wrote in
message
m...
"moreradio" wrote in message
.. .
I'm the proud owner of a nice SP-600, unfortunately it
is without tags, can someone help me to identify wich
version I have?
Here below some details:
-Non-mil radio no yellow anti-fungus varnish at all;
-Disc capacitors, no black beauty;
-The antenna connector looks to have been factory
modified to an SO-239 style to accept coax cable;
-Crystal deck with crystals
-Dial lock
-Gray front panel, white letters engraved.
thank you
Claudio
This is not enough information. There is a great deal
of information on the web, do a Google search for sp 600
jx to find it.
There were more than twenty variations of the SP-600
made, most nearly alike. The total production was on the
order of 25,000 units. Your description fits most of the
receivers with exception of the VLF special, the JX-17
(has two extra switches and three small red knobs) and
those made without the fixed frequency crystal unit. All
have very similar circuitry.
The receivers should have a name plate on top of the
tuning capacitor cover with serial number and version
type on it. These are somtimes missing.
The disc capacitors were used in receivers built
after the mid fifties but a great many earlier receivers
built with Sprague Black Beauty caps were modified due to
the very high early failure rate of these caps. Also many
receivers were modified to have the SO-239 connector
rather than the balanced coax connector originally used.
All of the JX-17s had these from the factory.
I am pretty sure the anti-fungus treatment was
applied after market and not all receivers have it.
Actually this is an advantage if you have to work on the
thing because the anti-fungus is very difficult to get
off and often glues things together.
At least one of the web sites has a list of versions
although its not quite complete.
--
Richard Knoppow
Los Angeles
WB6KBL
FWIW;
I have an SP600 with the JX17 designation on the the
tuner cover.
It has the balanced coax antenna connector, and coverage
from 540 kHz
to 54 mHz, and no red knobs. Of course, there's always
the chance
of a swap of tuner covers...
Nelson
The JX-17 was intended for diversity operation and has
connectors for the IFO (second conversion oscillator) with a
switch on the front and the BFO, also with a switch and aso
a connector on the fixed frequency assembly to use an
external HFO. This has an additional position on the
crystal-VFO switch. It has some other minor changes to the
circuitry: a different BFO circuit and fixed crystal
circuit, and the BFO injection level is fixed so it does not
have the injection pot on the back. These receivers were
made with the coaxial antenna connector rather than the
balanced connector used on other models, however many
receivers were modified to use the coax connector. Its not a
difficult mod but requires a lot of work.
Evidently, a lot of receivers were modified for
diversity reception with unsatisfactory results so
Hammarlund decided to offer a factory version. Most JXs,
however have means for more simple diversity work, namely an
IF output and access to the AVC and Detector lines.
If you want very high quality audio connect an
external amplifier to the detector terminals (needs a DC
blocking capacitor and is rather high impedance). The
detector itself has quite low distortion. However, note that
the normal AVC time constant is so fast that the level will
vary with low frequency modulation. The cure is to run it in
manual RF gain or to hang a rather large cap (a couple of
microfarads) across the AVC terminal on the back. This is
why the RF level meter bounces with modulation, it is
measuring carrier level.
A last note: The SP-600 is a very good receiver but I
think a lot of them are working but sick. The freqency
calibration and RF tracking should be very good but I think
the mechanical alignment of the tuning capacitor drifts with
time so a lot of them are not longer properly aligned. The
stators are held onto the frame with three clamp screws. The
stators should be exactly parallel to the rotor and exactly
centered. Also vertical alignment should be exact with the
edges of the rotor and stator plates in line when the cap is
closed. NEVER bend plates. Even though the end plates are
slotted they were never meant to be adjustable that way.
Once they are bent it is extremely difficult to ever get
them straight again and the stress will eventually break the
plates off the shaft.
Proper mechanical alignment requires removing the
tuning cap. This is a lot of work but not really difficult.
--
Richard Knoppow
Los Angeles
WB6KBL