Leak Trough Line Service Manual

Page 1

TFIDUGH LINE STEHED'
F. M. TUNER

INSTALLATION ° OPERATION ' MAINTENANCE

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CONNECTING THE F. M. TUNER

i. This unit may be used free-standing on a table, or it may be mounted on a panel of any thickness, through
a cut-out of 10%" x 35" (27-5 x 9-5 cms.). To mount on a. panel: take oh" the cover by removing the wing-
screw which passes through a hole in the cover fixing bracket and threads into a hank-bush in the centre
of the rear panel of the tuner. Pass the body of the tuner through the cut-out until the front plate butts
against the panel. replace the cover and wing-screw and tighten just enough to prevent the front plate on
the tuner from slipping on the panel.

2. The mains transformer primary is wound for voltages of 110, 117, I30, 210, 230, 250. (40 to 60 c/s). The
circular voltage selector (situated at the back of the tuner) should be withdrawn to its fullest extent, rotated
so that the arrow indicates the voltage nearest to your supply and then reinserted.

3. When used with a LEAK amplifier the mains supply for the tuner can be obtained by inserting the SUPPLY
POWER plug into the A.C. OUTLET socket on the amplifier.

4. The tuner is suitable for reception of mono broadcasts and stereo broadcasts using the world-wide standard
GE-Zenith system of transmission. To obtain optimum results from stereo transmissions it is essential that
the aerial terminals are fed with a strong signal. Although a short length of flex or inefficient indoor aerial
may give good results from mono transmissions, to obtain the lowest background noise on a stereo trans-
mission it is essential to use a first-class aerial correctly orientated. The optimum aerial position will be
indicated by maximum closure ofthe tuning indicator pattern. The 300 ohm aerial input is balanced to earth.
When using 300 ohm twin feeder. the conductors should be connected to the outer aerial terminals. When
using an unbalanced 70-80 ohm feeder, the inner central conductor should be connected to either of the
outside terminals and the outer screening connected to the centre chassis terminal.

5. AUDIO OUTPUTS. The two grey screened leads marked LEFT and RIGHT should be plugged into the

L and R TUNER input sockets on your stereo amplifier. The output level from these leads is much lower
than from the LEAK TROUGH-LINE II or TROUGH-LINE 3" tuners and the sensitivity of the
TUNER input of the associated audio amplifier should be approximately 50mV with an impedance of
47,000 to 100,000 ohms.
On LEAK valve pre-amplifiers the TUNER' pre-set input control should be turned to maximum. On the
STEREO 30" amplifier the slide switch be set to Hl' and resistors R5L and RSR may need changing
from 4,700 ohms to |5,000 ohms. Please write to us if you possess a "STEREO 30" amplifier with a serial
number below 208000 and we will send you these two resistors.

6. TAPE RECORDING. In addition to the audio signals the output contains some 38 kc/s and 76 kc/s
signals, the level of these signals being less than 5mV (-30dB on full output).

lfthis tuner is directly connected to a tape recorder then in some instances spurious whistles may be exper-
ienced due to the interaction of these signals with the bias and erase oscillator in the tape recorder. Some
tape recorder manufacturers are producing a filter for connection to the input of the tape recorder to
eliminate this effect.

If the tuner is connected to a tape recorder, via a LEAK amplifier, then a considerable reduction in level of
whistle will be obtained if during recording the pre-amplifier filter is switched to 9 kc/s.

7. The tuner is earthed to its associated amplifier via the screening of the AUDIO OUTPUT' leads, and no
additional earth connection should be made to any part of the tuner.

Page 2

OPERATING THE F. M. TUNER

B. FUNCTION SELECTOR

When receiving mono transmissions the selector switch should be set to MONO. When receiving stereo
transmissions the selector swrtch should be set to STEREO.

Although mono broadcasts will be received on both channels even if the selector switch is set to STEREO.
to obtain the lowest background noise it is preferable to use the MONO' position of the switch.

5. TUNE AND AFC
The tuning indicator used on this F.M. tuner is of the maximum closure type and only becomes operative
when the AFC is switched OFF. In order to tune in a station. it is therefore necessary to switch off the
AFC and adjust the tuning control until a minimum gap exists between the two vertical light strips. Switch-
ing the AFC ON locks the station in tune and removes the HT (13+) supply from the tuning indicator.
1D. SENSITIVITY

In locations of very high signal strength. the sensitivity switch should be set to LOCAL; following this
procedure will suppress some of the unwanted inter-station noise.

TUNE STEREO mono OFF

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