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MAINS VOLTAGE ADJUSTMENT
If your own Mains Voltage Supply differs from that given on the
first page of this Instruction Book (230-250 volts A.C.) then it
becomes necessary to re-set the Mains Voltage Tapping Panel,
which is found under the top deck of the TK20 in the topleft-
hand corner. MAKE QUITE SURE THAT YOUR TK20 IS DISCONNECTED
FROM THE MAINS SUPPLY. Removethe right-hand knurled knob (B)
by undoingits fixing screw with a small screwdriver. Lift off the
Recording Level/Volume Control (A). Now pull off the left-hand
Selector Switch (C). Next unscrew the four coin slotted
Brass Screws whichstill hold the Top Deck, then lift off the
Top Deck of the TK20. The Mains Voltage Selector Panel
is in the top left-hand corner and the different Voltage Settings
available are marked on the little square panel. Unscrew the
small screw from its 240 volt position and replace this into the
voltage figure closest to your own Mains Supply. The range over
which the voltage setting is most effective is shown as thefirst
item of the 'Technical Specification' in this Booklet.
THE DIODE CONNECTION
To install the Diode Connection in your radio set, you will need
two resistances, one of between 1 and 2 megohms(notcritical)
and the other of between 50,000 and 100,000 Ohms. These are
connected to the Volume Control as shown in the drawing below
and then taken by a screened lead to the TK20, preferably by
a co-axial Socket or jack on the Radio Chassis.
If p.c. is present on the Volume Control, the .o25 mfd. condenser
should be added between the Volume Control and the 1-2
megohmresistance, and if a very long lead is used for connection
to the Radio, the 35 pf condenser should be added. When using
this system an advantage is that the Input of the TK20is inde-
pendentof the volumesetting of the Radio.
| r--4
(-2Ma
|
TO DIODE INPUT
as
WY) OF TK20
FROM
J L--4 |
1
Xo
DIODE
| 'O25yuF 1
r--4 1
ea
1}
| SCREENED LEAD
TO AUDIO
35pF
| .
STAGES
OLUME
CONTROL |
36-100
|
|
Ka
CHASSIS
13
ADDITIONAL CIRCUIT
MAINTENANCE
After many hours use you may notice that sounds which should
have been completely erased when a new recording is made are
still present as a faint 'ghost' and that reproduction of the higher
frequencies tends to be weak. This is because microscopic par-
ticles of tape are sticking to the magnetic head. Thefrontof the
head should be cleaned with a small piece of wood such as a
matchororangestick, after first removing the front cover in front
of the sound channel (by pulling it upwards). All the head
assemblies are then accessible and maybecarefully cleaned.
It is also advisable to inspect the rubber pressure roller to ensure
that it is clean, and has not accumulated small particles of dust
or tape.
We must point out that your TK20 Tape Recorder is a very
delicate precision instrument and on no account should you
carry out any other adjustments or repairs yourself. As with all
precision instruments it will require a certain amount of main-
tenance after many hoursof use and this should only be done by
a competent Service Engineer.
STANDARD TAPE
LONG PLAYING TAPE
°
000
°
5
050
5
'o
100
io
so
Is
®
200
20
20
250
300
*
25
350
30
30
400
Chart of running time
os0
Feo
for
950
MINUTES
felele)
MINUTES,
Standard and L.P. Tapes
pos. INDICATOR
14
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