TANDBERG RC 20 User manual

TANDBERG
Remote
Control
RC20
Service
Manual
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Remote
Control
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Remote
ControlUnit RC20
The RC 20 remote
control svstem
uses
a
cordless,
infra-red
unit to control thelatest
Tandberg
tape
and
cassette
decks.
The system
consists
of a battery-driven
transmitter, anda receiver
which is con-
nected
to andgets
its supplyvoltage
from
the tape/cassette
deck.
The RC20 transmits
information with the
aid of infra-red
light (IR light) which is
invisible
to thehuman
eve.
Thetransmitter
unit RC207
Batterylife
The current
consumption
for thetransmitter
during use
is 12mA approximately.
The
battery has
a capacity
of about 200 mA
hours. So the battery will transmit con-
tinuouslyfor about17
hours.
Mechanical
dismantling
The transmitter
is held together
by two
screws.
One
of these
screws
islocated
under
thebattery.
Electrical
description
- The electronics in the transmitter consists
of two circuit boards. one board for the
pushbuttons (A1-1) and one board for
the IR unit (A1-2).
- The heart of the transmitter is a MOS
device
SAB 3210 (U1).
- When the push buttons are operated, the
transmitter is activated and current is
appliedto U1.
- The oscillator frequency is about 4Z kHz
and it isgiven
by Ll, C2 and C3.
- The IR output, pin 8, isnow active
and
the command signals
are applied to the
baseof Q2.
- Transistor
Q2 is abuffer the output IR,
pin 8, and the current generator consisting
of CR4, Q3, R8, and R9.
- The purpose of the current generator is to
regulate the current through the infra-red
light-emitting diodes to about 1.3 A irr
eachpulse.
NOTE !The transmitter must not be <tperate
d
with diode
CR4 disconnecte
d.If it is
opcrated
with CR4 disconnected, a heavy .r.l.r.rrt -ill
flow through diodes CRI - CR3 and thev
will de destroyed.
- CR4, which is a red light-emitting diocle,
will flash in stepwith the current through
diodes
CRI - CR4.
- The IR signal
consists
of one start-bit and
six information bits. An overview of the
pulse sequence
is given in table 1.
R

ransmitter
- RC207 Receiver
- RC20R
Control
operated Bit
sequence
attheoutput
of Ul, pin 8
(transmitter) Logic
levelsatthe
outputsof Ul
(receiver)
ABCD
Logiclevels
atconnector
pin
No.:
12457
Wind
and
Rewind
Stop
Stop
and
Wind
Stopand Rewind
StopandPlay
Rewind
Record
(both)
Play
Wind
1Omsapprox. --{
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0000
1000
0100
0010
1010
0110
0001
10110
11011
01110
11110
11101
11001
10111
It
LI
Table 1
-1
=Q
Receiver
unit RC 20R
Functional description
The receiverhastwo main functions:
- One function is to convert the IR light
from the transmitter to electrical signals
which operate the tape deck according to
a system of command signals.
- The secondfunction is to select(with the
aid of other controls) whether the tape
deck goesover to Play or Record when a
Timer is used. A Timer switches on the
power to the tape deck automaticalll' at a
chosen
time.
E
lectrical
description
- The IR amplifieris located
on the top
circuitboard(A2-1) in thereceiver
unit.
- The receiverdiode
CR1is verysensitiveto
IR lightand
thediode
isequipped
with an
opticalfilter whichmakes
it insensitive
to
visible
light.
Thecircuitisdesignedto suppress
i00/120 Hz light from incandescent
lamps.
Thisis
importantsince tape
decks
are often usednear to strongartificial
light.An incandescentlamp
radiates30%
of itspower
within thesensitivespectrum
of CR1.

The Decoder
- The heartof the decoder
is Ul a MOS
integratedcircuit,
type SAB 3209,which
has
a
built-inclock.Theclock frequency
isabout
43 kHz andit isdeterminedby
L1,C1,
andC2.
- In this application specialprogrammable
outputs
areused
-,A, B,C,and
D. The
levels
at theseoutputs for the different
modes
of operation
areshownin table1.
- Logic circuitsU2 to U6 provide the
interfacebetweenU1 and the Remote
Controlinput on the tapedeck.All the
line outputs terminatein gates
in U6.
- Table 2 showswhich remote control
outputs are activated when particular
buttonsare
pressed.
Activeoutputsmean
that they go to logiclow (0), between
about
+ 0.1
V and
+ 0.3
V.
- Diodes
CR3 andCR4 providean extra
functionwhichsends
thePlayoutput to
low (0) when the Record button is
operated.
Oueruiewof therelation
betweenoperatzon
buttons
andremotecontrol
outbuts
* Whenthe Recordbutton is
pressed,
both the Recoro
andPlay outputswill always beactivated.Thisavoids
the needfor aseparate button on the transmitter
for
the "flying start record" facility. lf both Rec.
Select
buttons
areintheOff position andthe Recordbuttons
on the transmitter
areoperated.the tapedeck will
remain
in the Stop mode. lf the Record
buttonsare
released
the tapedeck will go into the Play mode.
*i This combination at the output is used only on
individualmodels.
Fault
findingtips
Equipment required: Oscilloscope, fre-
quency
counter,
voltmeter,
highimpedance
measurementprobe.
Transmitter
RC207
1.The light diodeon the operating
panel
doesnot blink when the buttons are
operated.
Replace
thebattery.
2.Use thehigh
impedance
probe(> i MO)
onpin 18,
U1.Thecircuitshouldoscillate
at about 43 kHz when the buttons are
pressed.If it doesnot oscillate,
seepoint
J.
3.Check
thatpin 6,Ul goes
low when
the
buttons areoperated.
If pin 6 goes
low,
seepoint4.
4. Use
anoscilloscope
to check
thatpin 8,
Ul has
a bit sequence
asshownin the
table.
If not, checkthesupplyleads
from
the operation
buttons andif necessary
change
U1.
5.Use
anoscilloscope
to measure
thevoltage
acrossR8 andR9.Thevoltage
amplitude
of the pulses
shouldbe between0.55V
and0.75
V. If not. checkthediodes
and
Q3.
Receiver
RC20R
1.
The receiveris supplied with an unregu-
latedvoltageof about14V d.c.
Check
at
C6that Ql regulatesthevoltage
to about
10.5
V d.c.
2.Checkthe receiverpre-amplifierwith an
oscilloscopeprobeon thecollectorof Q7.
Thepulse
sequenceshould
bein opposite
phaseto the pulsesequence shown in
table1.
3.
CheckUl with a
probe
onoutputsA, B,
C,and
D. Seetable1.
Button
operated
on
thetransmitter Outputactivated
in
thereceiver
PLAY
STOP
WIND
REWIND
RECORD*
(both)
WIND
andREWIND
STOP
andWIND
STOP
andREWIND
STOP
and
PLAY
PLAY
STOP
WIN
D
REWIND
RECORD
and
PLAY
WIND
and
REWIND
STOP
and
PLAY**
STOP
and
PLAY**
STOP
and
PLAY**

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RECEIVER
PRE.AMP
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RECEIVER
DECODER
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INTERGRATED
CIRCUITS
USED
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1 -SAB 3209
. IR RECEIVER
U2 -MC.I/.001
B, OUAD2-INPUINORGAIE
(cMos)
U3.5 -MC110118,
OUADz-II.PUI
i{ANBATE
(cMos)
U6 -HINIL332, HEXINVERTERGA,TE,OC
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TRANSMITTER
Transmitter,
Keyboard
seen
from solder
side. Transmitter,
IR-board
seen
from solder
side.
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1704
-8 -79 Part
No.714126
Printed
inNorway
by Reclamo
A/S
TANDBERG
INDUSTRIER
A/S
ELECTRONIC
DIVISION
P.O.
Box
55,
Bogerud
N-OSLO6-Norway
toard
ide.
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