Counter Buffer Amplifier Circuit

TM 11.58951097.40

(4) Comparator U6B. The signal level

supply components mounted on the main circuit card.

detected from the buffer amplifier is compared against

These consist of CRI and CR2 which rectify the ac input

set voltage levels. The output of the comparator is fed to

to + 26 + 2 Vdc and feed it to the 12 volt regulator U1.

logic NOR gate U7D.

(1) The 12 volt regulator UI supplies + 12

(5) Xmit logic U7A and U7D. The comparator

0.5 Vdc to the 6.2 volt regulator U2, and the + 12V jack

output is fed to U7 which verifies the correct signal and

on the front panel, the RF amplifier of the RCVR XTAL

performs inversions where they are required. If the signal

MODULE, the first mixer, the overtone amplifier, the xmit

is correct, NOR gate U7D would bias the GO driver Q 11

xtal circuit, the counter buffer circuit, the indicators, and

to light the GO lamp. If the signal is incorrect, U7A, by

the lamp drivers.

inversion of U7D output, would bias the NO GO driver

(2) The 6.2 volt regulator U2 supplies + 6.2

Q10 to light the NO GO lamp.

0.1 Vdc to the local oscillator of the RCVR XTAL

c. Counter Buffer Amplifier Circuit. The counter

MODULE, second mixer, second local oscillator, if.

buffer amplifier consists of a high frequency amplifier

amplifier, comparator U6, logic U7, and the + 6V jack on

(Q15) and a low pass filter. Q15's base input is the

the front panel.

overtone frequency of either the rcvr or xmit circuits,

e. Xtal Select Switch SW3. The xtal select switch

whichever is being used. The input is amplified and

SW3 is a DPDT switch which connects either the xmit

matched by the use of pulse transformer T5. The signal

xtal circuit or the rcvr xtal circuit to the lamp drivers Q10

is capacitively coupled to a low pass filter consisting of

and Q11.

C19, C20, and L3 which prevents any harmonics from

f. Test Select Switch SW2. The test select switch

appearing at the COUNTER OUTPUT connector.

is a DPDT switch with a spring loaded center off position.

d. Power Supply Circuit. Dc power is provided by a

It connects the GO/NO GO indicators momentarily to the

full wave center tapped rectifier circuit consisting of a

lamp drivers Q10 and Q11, or momentarily to ground to

center tapped transformer TI, mounted on the front

test the functioning of the indicators.

panel, which provides 28 Vac to the rest of the power

2-3