Zenith royal 7000 1

Page 1

GENERAL

The Royal 700 _, .- i -. peceiler covers a wide»

range of frequencies w ich provide the operator with coverage
of: FM, Longwave, Standard Broadcast, VHF Weather Band
and seven Shortwave bands. It operates on eight lfivolt D"
cells which provide up to 300 hours of performance under
normal operating conditions and has a ninth 15/; volt battery
which is used to power the dial lights and also the chart light.
A 4" x 6" oval speaker is used for excellent reproduction and
delivers undistorted power output of 500 milliwatts. This
receiver can also be user' as a FM-AM tuner in conjunction
With external high fidelity audio equipment

An earphone jack has been provided so that the user can

connect a set of Zenith low impedance headphones (part no.

39-34) or a Zenith hearing aid type low impedance earphone
' (part no. 39-75). .

A Waverod antenna which is stored in the cabinet top is used
on the FM, VHF and Shortwave Bands. The Standard

Broadcast and Longwave Bands have a kLiilt-in Wavemagnet
antenna which eliminates the need for an external antenna
under average conditions Provisions have also been made for

external antenna connections,

FM SECTION

Separate tuners are used on the FM (88 to 108 MHz) and the
VHF Weather Band.

The FM (88 to 108 MHz) tuner consists ofa RF amplifier plus
an autodyne converter (mixeroscillator) while the VHF tuner
has an RF amplifier and separate mixer and oscillator
transistors. Following the tuners there are three LF. Stages,
Ratio Detector, first audio, pre-driver, driver and diode biased

class B" push-pull audio output.

The FM R.F. and .Autodyne converter stages operate in
common base circuits. Three LF. stages are comtnon emitter

, circuits and have slug tuned 1.F, transformers operating at 10.7
MHZ. To eliminate over! 3 and [55 lie n in the
IF. passband and in the . curve of the Ratio Detector, AGC is
obtained from the collector of the 2nd 1.17.. This AGC voltage
is taken thru a 6 pf. capacitor to diode X2 and fed to the base
of the RF transistor as reverse bias. The IF signal is reduced
to audio with a conventional Ratio Detecto cotporating :wo
matched solid state diodes which are located in T 13.

On the VHF Band the RF stage operates in a common base
circuit while the mixer and oscillator transistors are common
emitter circuits. A fixed frequency crystal controlled oscillator
is used for operation on the VHF Band. The frequency of
operation is determined by the crystal selected. Any time a
crystal is replaced the receiver must be rea1igned. A.F.C.
voltage is not applied to the VHF tuner due to the normal
stability of crystal controlled oscillators. The remainder of the
circuits are as explained above with the FM tuner.

AUTOMATIC FREQUENCY CONTHOL (AFCl

As with all high freqL-..-;. c...a rs . .
is desirable to provide Autom tic Frequency Control, which is
guided by voltages, directly related to oscillator frequency
shift. Automatic Frequency Control is accomplished by taking
D.C. Voltage from the tertiary winding of the Ratio Detector
and feeding it back to die 4, w a ve
variable capacitor. This diode is connecte across the osc ato
portion of the autodyne circuit and acts as a frequency
controlling device. if the oscillator shifts frequency, it causes
ratio detector unbalance and a DC. voltage is fed back to the
diode. Changing capacity of the diode will automatically
adjust the frequency ofthe oscillator circuit to compensate for
original oscillator shift. in this manner, we have continuous
oscillator Automatic Frequency Control.

The lock-in range of the AFC circuit is approximately 700
KHz at 100 micro-volts. Should you desire to receive a weak
FM station within the AFC pull-in range of a strong FM
station, an AFC disabling switch has been provided in the
receiver circuitry. The AFC voltage is removed from the
oscillator when the AFC switch is placed in FM position.

To obtain proper AFC action, place the AFC switch in PM
position and tune to the exact desired station frequency; then

out the AFC switch in the AFC position. . .this will insure

proper AFC action.

1 new; A r n G: u :9 :murv nae lo
m. u. H to ..t..b.l.t, .. upon... . ..

no ..

AM SECTION t,»

On AM operation this instrument utilizesqa conventional
superheterodyne circuit using indiVidual mixer and oscillator
transistors to produce the 455 KHz intermediate frequency.
The LF. frequency amplifiers are conventional in design. The
diode (part of T14 assembly) is usas a detector and AGC
voltage source. This is then followed byieshe first audio
amplifier, a pro-driver, and a driver stage for' inc diode biased
class B push-pull output.

. ' ' u,

' m : , 141,7

Page 2

On AM. the R.F. stage uses common base circuitry for L.W.
and B.C., but is common emitter on all Shortwave bands. The
oscillator transistor uses common base circuitry, while the
mixer and I.F. transistors have common emitter circuitry.

AGC voltage is supplied from the AM diode detector to the
base of the RF transistor. The AGC voltage is then taken from
the RF emitter and fed to the base of the mixer and first If.
transistor.

AUDIO SYSTEM

The audio system is common to both the FM and AM. Output
from either the FM Ratio Detector or the AM Detector is fed
to the base of the 121-430 first audio, and then to the
121-430 pre-driver, the 121441 driver and into the diode
biased class B push-pull output stage consisting of one
1217678 and one 121-679 transistor.

Provision has been made for use of this receiver as a tuner in
conjunction with high fidelity equipment through the use of
an output jack located on the upper rear of the cabinet. The
volume control on the Royal 7000-1 must be at mini
volume position to eliminate sound from the re
speakers.

OUTPUT TRANSISTORS

The output stage of this receiver consists ofa matched pair of
one 121-678 and one 121-679 transistor which function in a
complementary symmetry push-pull, class B" audio circuit.
These transistors are grouped by beta ratings and are color
coded accordingy. Ifone ofthese transistors fail, replace both
output transistors with a new matched pair which will be
stocked as part 110800-245. Care must be taken to replace the
transistors in the proper sockets so that they will function
properly and provide a balanced output.

COMPONENT REPLACEMENT

When soldering components at the base ofa transistor socket,
it is suggested that the transistor be removed to avoid any
possrbility of excessive heat transfer through the pin connec-
tion to the transistor. When soldering the low voltage
electrolytics and diodes. the wire leads should be held with a
pair of long nose pliers. The long nose pliers will act as a heat
sink.

TROUBLE SHOOTING AND SIGNAL TRACING

The old technique of screwdriver testing" is definitely not
recommended while trouble shooting any solid state product.
In that method various circuit points were touched or shorted
to ground to cause a hum or click in the speaker, This must
be avoided because a solid state component can be destroyed

-r> ._....;..l ..-ir..M -. : ....,._~ ..,. m... .m "a; \7 It ran .
u CAUCbDIV/E VUILQEC u: if wrung voltage vau-rfi, u uppltcd.

Only standard point to point signal tracing with the proper
RF, 1F, and Audio Signal Sources sltOUId be used.

BATTERY OPERATION

Eight Zenith part number Z4NL 15: volt or standard 0 type
flashlight batteries. Approximate battery life of up to 300
hours. One Zenith Z4NL battery is used for the chart and dial
lights. Normal no signal current drain is approximately 25
milliamperes.

AC OPERATION

This receiver may be operated from the standard 115 or 230
volt alternating current suppIy. To do this Zenith engineers
have designed a built-in power supply and switching circuits
which allow yon.to select between battery operating or AC
operation. This change-over is made by inserting the AC pOWEr

- ;. . i'» t t I '- I .,' . Al - t ._ . AI.
Hit 1.! .tit .ticmr t-...L.u tin I.It' tum... rt.:t. Iiistdc mt

receiver is a switch which permits selection for operation on
either 115 or 230 volt AC power lines.

IMPORTANT: IF THE RECEIVER IS NOT TO BE OPERA-
TED ON BATTERIES FOR SEVERAL WEEKS, THE
BATTERIES SHOULD BE REMOVED.

TUNING RANGES

Band Meters Mega Hertz Kilo Hertz
7 7 ,(M) (MHz) (KHz)

VH1" 1.25 * *
FM 3.4 to 2,8 88 to 108 88,000 to 108.000
LW 2000 to 750 .15 to .4 150 to 400
BC 555 to 188 .54 to 1.6 540 to 1,600
SW 1 188 to 85 1.6 to 3.5 1,600 to 3,500
SW 2 85 to 33 3.5 to 9.0 3,500 to 9,000
31 3] 9.4 to 10.1 9,400 to 10,100
25 25 11.4 to 12.3 11,400 to 12.300
19 19 14.6 to 15.8 14,600 to 15.800
16 16 17.1 to 18.5 17.100 to 18.500
13 13 20.6 to 22.4 20,600 to 22,400
Intermediate Frequency ........ AM - 455 KHz

FM - 10.7 MHZ

* This receiver is shipped with a crystal installed for operation
on 162.55 MHz. The crystals used are of the third overtone
type. To determine the operating frequency, multiply the
crystals fundamental frequency times three, and subtract 10,7
Evil-Ix. Example:
57.75 MHz
X 3

173.25 MHz
»IO.7 MHZ

162.55 MHZ

AM OSCILLATOR BIAS ADJUSTIIENT

Stability of the AM Oscillator may be maintained over a wide
range of battery supply voltages If a variable DC voltage
supply is available adjustment may be made as follows:

4-51 .A ...

1. Set Manual Gain COllllUl LU maxrmuu. c
tion.

2. Rotate Band Switch to 13 meter position.

3. Connect the positive end of a 4% volt battery to Test
Point 3 while the negative end is connected in series with
a volt meter. The other end of the meter is connected to
Test Point 6. There should be a meter reading of
approximately 0.5 to 1.0 volt.

4. Adjust Bias Control R19 for minimum Voltage change on
the meter while varying the DC supply between 8 and 12
volts.

5. Return Manual Gain Control to the Normal position.

BATTERY LEVEL METER ADJUSTMENT

This receiver is equipped with a combination Tuning and
Battery Level Meter which will indicate the condition of the
batteries being used. A meter reading in the blue section
indicates good batteries. Under normal conditions no adjust-
ment should be necessary. If the meter has been replaced or
other repairs made which affect the meter circuit, adjustment
may be made as follows. Use a supply of 9 volts and while
holding the Dial Light/Battery Level switch in the BAT-
TERY LEVEL position adjust control R51 so that the meter
pointer lines up with the left edge of the blue section of the
meter.

ALIGNMENT

3.
Alignment wrenches, Zenith part number 68-32, 68-35, and
68-45 may be used for aligning this receiver. Charts for proper
alignment are included in this service manual