TM 55-4920-399-13&P
e. Pin 34 shall produce a square wave of 5 Khz. Pin
29 shall produce a square wave corresponding to the
20 is +15V. Pin 18 is -10V (TTL supply), pin 2 is -15V,
LO Z Voltage as shown on Figure 4-5.
and pin 3 is ground.
f. Pin 12 should show square wave with a positive go-
ing- edge, sometime when pin 10 is high (the phasing
a. Pins 1,5,7,9, 11, 13, and 15 are inputs from the Al
depending on the capacitance being measured, provid-
Digital Board and are TTL level signals. Pins 4,6,8,10,
ed unit is not over-range).
12,14, and 15 correspond to pins 1,5,7,9,11,13, and 15
respectively. The signals are complements of the input
.
g. Pin 30 should show a pulse of approximately 250ns
signals and vary from -15V to ground.
width (possibly undetectable) when pin 12 goes high.
Pin 13 should be high at all times, except it should be
low when unit is over-range.
b. Pin 19 varies from 0 to +15V and pin 17 varies with
pin 19 from -15V to -10V (TTL level).
h. Pin 15 should be high except when unit is over-
range. At those times, Pin 15 should toggle at a rate
of one half the rate seen on pin 14.
4-9. LO Z Board A5. (Refer to FO-5.) Power: pin 9 is
+15V, pin 8 is -15V, and pins 2 and 7 are ground.
i. Pin 31 is Vcc and is +5V referenced to -15V and
is -10V referenced to system ground. Pin 11 is -15V,
referenced to system ground.
a. Pin 6 is a 5 KHz square wave (approx) of TTL lev-
el. Pin 1 is a 5 KHz sine wave (approx.); it is the LO Z
output.
is +15V, pin 8 is -15V, and pins 1 and 10 are ground.
a. Pin 6 should be +15V and is the source for the un-
b. Pin 3 is a square wave, corresponding to the LO Z
known resistor to be measured. Pin 7 is the input to
voltage as shown on Figure 4-7. The output varies be-
the megohmmeter and the unknown current from the
tween -15V and -10V.
resistor being measured flows there. It is a virtual
ground and should be at OV.
12 is +15V, pin 14 is 15V and pin 15 is 10V (refer-
vary logarithmically from lV to 10V, depending on the
enced to system ground). Pin 16 is 7V (unregulated).
unknown resistance being measured.
Pin 13 is ground. Pins 3 through 10 are on T1 secondary.
c. Pins 4 and 5 go to the offset adjust pot. Pins 2 and
Pins 1 and 2 not used.
3 go to the gain adjust pot.
4-7. Analog/Digital Board A3. (Refer to FO-4.) Pow-
4-10. Display Board A7. (Refer to FO-6.) Power: pin 1
er: pin 13 is +15V, pin 23 is -15V, and pin 12 is ground.
is +5(10V referenced to system gound) and pin 2 is OV
a. Pin 9 should be the LO Z voltage. Pins 18, 5, 21,
(-15V, referenced to system ground). Pin 23 is -7V, un-
16, and 14 should go to the single point ground (lugs
regulated.
on teflon sleeve, located next to mode switch).
b. Pin 7 should be a square wave, varying from -15V
a. Pin 10 should show a pulse, approximately 250ns
to ground and shall be approximately 5 Khz (equal to
wide (possibly undetectable), corresponding to pin 30 on
LO Z frequency). Pin 8 is the same square wave, ex-
Al Digital Board.
cept it is the complement of pin 7.
c. Pins 15, 1 and 4 shall correspond to the three-phase
b. Pin 21 is connected to pin 15 on Al board and should
clock, except that they vary from -15V to ground. Pins
be high unless unit is over-range and should then toggle
15, 1 and 4 correspond to pins 5, 6 and 10 respectively
at a rate half that of pin 10 on Al.
on the Al Digital Board, except for the voltage
difference.
c. Pin 22, connected to pin 13 on A1 Digital board,
should be high except when the unit is over-range, then
justment pos.
pin 22 should be low.
e. Pin 17 should go high sometime during the period
d. Pins 4,5,6, and 7 represent the least significant dig-
when pin 4 is at ground, unless the unit is over-range. If
it and should have a BCD count from 1 to 9; the same for
that is the case, it will go to ground and stay there.
pins 8, 9,11,12 and 13,14,15,16 and 17,18,19,20. Each
group of four represents a more significant digit and is
connected to the outputs of the decade counter on the Al
ured. It is a virtual ground and shall be at OV.
board.
4-2
Change 1
