Dear all on the list,
Good morning and good evening from Japan.
I got kind association of Hallicrafters users through their nice information.
I really appreciate all of their supporting for me.
Though I am not ready to make my final conclusion,
I'm reporting the capability of the right place for the capacitor C134
in the schematics of Hallicrafters FPM-300 MK II transceiver.
Will you please let me know your agreement, objections or another idea,
if you got any idea?
I made my idea from three view points as follows:
1) The capability from the 'Numbering' assignment as C134;
In the schematics,
I focused on the order 'Hundred' sequence for capacitors.
For example,
C1xx is assigned for a capacitor on the mother chassis.
C2xx is assigned for a capacitor on a PCB of the 9MHz function module.
C3xx is assigned for a capacitor on a PCB of the Power supply filter module.
C4xx is assigned for a capacitor on a PCB of the VFO / Pre-Mixer.
C5xx is assigned for a capacitor on a PCB of the Preselector ALC module.
C7xx is assigned for a capacitor on a PCB of the 25kHz calibrator module.
Then, the capacitor C134 should be on the mother chassis which includes
the power transformer, the DC-DC converter, the bus line for signals,
B+, B-, RF power driver, RF power amplifier, PA load tunes and controls.
Again,
I focused on the order 'Decade' sequence for capacitors.
For example, mainly,
C10x is assigned for the capacitor at the external terminal circuits.
C11x is assigned for the capacitor at the RF power amplifier circuits.
C12x is assigned for the capacitor at the PA load tunes circuits.
C13x is assigned for the frequency bypass capacitor at the intersection to
the external terminal circuits, in order to reduce the impedance of the
heavy load, I suppose.
2) The capability from the parts specification for C134;
C134 is specified as 0.01uF with 25V, Ceramic.
(a) I suppose that 0.01uF value with Ceramic will be used for
the RF process range.
(b) I suppose that 25V value will be used for the 12.6V Power supply
bus line.
3) The capability from comparing with other transceivers in mid '70;
I checked the Power supply of Yaesu FT-301 transceiver which
had been released in mid '70, as follows URL:
https://www.dropbox.com/h
FP-301 Power supply has a bypass capacitor 0.01uF Ceramic, at the
13.5V B+ bus power output line, which is not installed in FPM-300.
4) Conclusion;
Then, I made my decision that the capacitor C134 as a bypass capacitor
should be attached into the intersection between the capacitor C131
(3000uF, 25V) and the choke coil L101 (100mH), in order to reduce the
impedance of the heavy load by the 12.6V power bus lines for all PCBs.
> Recently, I got a transceiver, FPM-300 MK II, with the service manual.
> I found however no-matching between the parts list and the schematics.
> Because there is no capacitor, C134, in a schematics, although it in
> the parts list of the FPM-300 MK II.
> I found this capacitor, C134, had been added for the Mark II into the
> original FPM-300 circuits.
Again, I appreciate your associated supporting for me.
Best regards,
Katsuhiko Hirai, JA3ECA, exN8EYH/Dayton OH
Ikoma city, Nara, Japan
--
Katsuhiko Hirai <mxc04040 at nifty.ne.jp>