Ramsey Electronics FX-440 Manual page 127

button instantly reverses the status of 012, 013 and 014 to return to
receive mode.
~
J,il70 limits the current drawn by 017 to a safe level. This LED usefully
assures that the otherwise-silent PTT circuitry is indeed functioning and
obviously has nothing to do with the RF output of the transmitter.
The PTT circuit may also be activated at pin 3 of the Packet 1/0 jack. A
direct short to ground is not necessary. The author noted very positive
- PTT action with resistance as high as 1 OOK from pin 3 to ground.
This is a highly reliable and efficient. PTT system provided that careful
attention is given to correct selection wid ir:istaflation of all parts: resistor
value5, PNP transistors, zener diode orientation, U4 installation, correct
wiring of microphone jack. ·
Stage M:
ASSEMBLY PROCEDURE:
Install the following parts:
[ ] [.JM1: C86, .001 uf(marked .001 or102or1nf).
'
[ I [ l
M2: C83, .001 uf.
[ I [/]
M3: C88: .001 uf.
[ I [ I
M4: C77, .001 uf.
[ ] [,] MS: C23, .001 uf.
[
t··[~-LM6:
R57, 2.2K (red-red-red).
[ )
{~·')
M7: R59, 1 OOK (brown-black-yellow).
[ ] [.c:J
M8: R58, 270 ohms (red-violet-brown).
[ ) ] M9a: R50, 1 OK (brown-black-orange).
[ ] ( ] M9b: R49, 1 OK (brown-black-orange).
( ] ( .;I
M1-0: R51, 47K (yellow-violet-orange).
t.
( ] ( {] M11: R56: 47K (yellow-violet-orange).
[ I l'i I
M12: R61: 2.2K (red-red-red).
[ I
d
I
M13: R37: 220K (red-red-yellow).
[ I [ \]
M 14: C93: 4. 7 or 1 O uf. (Watch polarity!)
FX-#iO
Assm. 65