Post by tomcathamI would very much appreciate your help. The unit has been
recapped and
the resistors shot gunned, most of the postage stamp caps
or still in
the cans and drum. At this point it looks like the wring
may not be
reconnected as it should be. I am checking voltage and
resistants now (
not good). I have no sound from any band with ant.
connected (nothing).I
can put 400cps modulated at 455 signal at the imput and
can trace the
signal through the unit. I have every book I can find on
the SP600 and
the JX-17.
I could very much use voltage for the following, T-8 pins
left to right
and 1 at the top, E13-1 through 10, E14- 1 through 8,
E15- 1 through 8,
E 16- 1 through 8, E 17 1 through 15.
This is a learning process for me, so some of the
questions will show
how wet behind the 70+ ears I am.
Thank you for reading
Jimmy K5CSU
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Do you have the military manual TO 11-851? There is a
high resolution version on the web. It shows the chassis
layout of most of the versions of the SP-600 and gives
transformer voltages. You should be able to find the numbers
on the schematic and the bottom of the transformer should
have the corresponding numbers on the transformer terminal
board. Pages 105 and 106 show voltages and resistances at
the terminal boards.
Go over your recapping to see if you have mis-wired
something.
Note that socket voltages except for grids are given as
measured with a 1000 ohm/volt meter, more modern 20,000
ohm/volt meters will read high. Grid voltages are measured
using a VTVM. With the correct meter the chart voltages are
close to what you should get.
The BB caps should always be replaced but the postage
stamp caps are silver mica types and seldom fail, although
they can. They should not be shotgunned and those on the LO
modules of the turret are precision values.
Before anything else make sure you have not accidentally
left the REC-Standby switch in Standby. Also make sure there
is a shorting wire across the diode load terminals at the
back. Also make sure the crystal selector is in VFO although
you should hear some noise even it its in one of the crystal
positions. Clean the decks of the selectivity switch, it can
cause the receiver to appear dead when dirty.
For trouble shooting first check the power supply
voltages as given by the tube socket chart. This will start
you and may find the problem. Check to make sure the tubes
are in the right sockets.
First, check the power supply voltages as given by the
tube socket chart.
Check to see if the receiver is dead on all bands or
only on the double conversion bands (upper three).
If its dead on all bands use a second receiver (a
broadcast receiver will do) to listen for the local
oscillator.
Did you remove the RF deck to replace the caps there?
If so did you remember to set the turret to half-way between
two bands before re-installing it? If not you may have bent
up the contacts on the deck. These are not supposed to be
repairable but I have managed to make bent and broken ones
work again with very careful straightening and soldering.
If you can inject a 455 khz signal and hear it the
problem would appear to be in the RF section. I would start
with the LO, then first mixer, then the two RF amps. Run the
set on a single conversion band to simplify things.
If this is a JX-17 make sure the red knobs are not in
external.
Some sets have transformers with square bottom terminal
boards and some have round ones. The military manual covers
both.
--
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Richard Knoppow
Los Angeles
WB6KBL
The power Transformer hsd the ac voltages stamped on it. Have yo