Detector and Electrometer Assembly A201

Cathode bias is employed; the bias

The fourth if. amplifier ( V 2 1 0 ) operates

r e s i s t o r is bypassed by a capac-

i n a n i d e n t i c a l m a n n e r w i t h V209. The

itor. A tuned coil is in series with

o u t p u t signal from the tuned impedance

the cathode bias network to chassis

n e t w o r k 2202 is coupled to if. cathode

ground. This coil is adjusted dur-

follower V211.

i n g if. amplifier alignment to de-

d. If. Cathode Follower V211 (fig. 32).

velop maximum signal output.

A cathode follower is used as the final

(3)

The c o m m o n junction of the

s t a g e in the if. amplifier subassembly.

s c r e e n grid, the suppressor grid,

T h i s stage is identical in circuit compo-

and the plate is bypassed to ground

nents with the if. cathode follower in tuning

t h r o u g h a capacitor. Plate volt-

units 2, 3, and 4. Therefore, the following

a g e is applied from the filtered

c i r c u i t description is applicable to all if.

1 5 0 - v o l t bus through a dropping

c a t h o d e followers, with differences indi-

resistor.

cated in the chart that follows the circuit

analysis.

(4)

The heater circuit is decoupled

from the 6.3-volt ac power

(1) The function of the if. cathode fol-

s o u r c e by a filter capacitor and

lower is to supply driving power to

rf choke.

t h e detectors in the detector and

e l e c t r o m e t e r circuit from a low-

T h e rf voltage developed across

(5)

i m p e d a n c e source.

t h e cathode tuned coil is applied

t o a connector plug on the rear

(2) A pentode-type 6BJ6 tube is used

p a r t i t i o n of the if. amplifier sub-

a s the if. cathode follower; since

a s s e m b l y. This connector plug

the screen grid, the suppressor

mates direct with input jack J1 on

g r i d , and the plate are externally

t h e detector and electrometer as-

connected together, the tube func-

sembly.

t i o n s like a triode. The if. signal

from the final if. amplifier is cou-

(6)

T h e following chart summarizes

pled to the grid of the triode. The

the differences between the if.

r e s i s t o r housed within the imped-

c a t h o d e followers in tuning units

2, 3, and 4.

ance network of the final if. ampli-

f i e r functions as the grid return.

Tuning unit

Component

If. cathode follower

V211

V512

V410

Grid input parasitic suppressor

None

R462

R584

Cathode bias resistor

R271

R463

R585

Cathode bypass capacitor

C293

C488

C593

Plate voltage-dropping resistor and bypass capacitor

R272 and C294

R464 and C491

R586 and C594

Plate decoupling network

R269 and C295

R459 and C492

R581 and C603

Heater decoupling circuit

C306 and L235

C489 and L432

C609 and L542

Tuned cathode inductance

L431

L229

L535

P212

P413

Output connector

P514

separate audio and dc metering signal

41. Detector and Electrometer

channels, and applies output signals to the

Assembly A201

appropriate circuits in the main unit.

(fig. 19)

T h e s e sealed assemblies are interchange-

able with each other and perform the func-

All tuning units use an identical sealed

t i o n s described in detail for detector and

d e t e c t o r and electrometer assembly. Each

e l e c t r o m e t e r assembly A1 within tuning

assembly receives driving power from the

unit 1 (para 32 and 33).

i f . amplifier, s e p a r a t e s the signal into