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Service Manual T51
Issue 1.0
DiVA T51
AM/FM Tuner
ARCAM
Contents List
! Contents list
! Circuit description
! Circuit diagrams
! Component overlays
! Circuit board parts list
! General assembly parts list
T51 Tuner Circuit Description
Stereo Decoder
Power Supply Stereo decoding is performed by LA3401 (Z8). The 38kHz
reference signal is accurately created by ceramic resonator
Mains voltage selection is made by placing a fuse, of X3 and does not require adjustment.
appropriate value, in the 115V or 230V position. Stereo separation is adjusted for maximum by preset RV1.
The single secondary is rectified and regulated and This IC also contains FM/AM audio switching and muting
supplies four regulators. functions.
Z7 is always powered when the mains is connected and
keeps the preset memory of the micro controller intact. Audio Filters & Output
The high-value capacitor (C84) will keep this data safe, for
a limited time, in case of mains power failure. The left and right channel audio outputs from Z8 are
filtered by the de-emphasis network of R1, C1 etc. The
Z5 provides the main 12V supply rail for the RF and audio correct de-emphasis network is selected by the position of
circuits. This is always connected, except for the supply to jumpers JP3 & JP4 on the pins of SK8. C2 & C102
the FM front end, which is disabled by Q2 when the unit is (220pF) are selected for 50us and C3 & C103 (560pF) for
turned 'off'. 75us de-emphasis.
Z4 powers the LED back light on the display PCB. The final filter, based on Z3, is a two-pole low-pass circuit
with a cut-off frequency of around 20kHz. Also included
Z6 is the 5V digital supply for the micro controller. is a 19kHz notch filter, L1 & C4, that removes most of the
residual pilot tone.
FM Tuner & IF
Muting
The FM aerial input is mixed in the front end FE1 which
provides a 10.7MHz IF output. This is filtered and When the power switch is turned off Q5 is switched off,
amplified by ceramic filters CF1 & CF2 and the circuit enabling the mute circuitry of the stereo decoder (Z8) via
based around Q9 & Q10. A third filter CF3 can be put in diode D9. This removes the need for output muting
circuit by fitting jumpers JP1 & JP2 across pins 2 & 4 and transistors and eliminates switching clicks and pops.
1 & 3 of SK6 respectively. This effectively narrows the IF At switch-on the mute is enabled while C21 is charged via
band to improve selectivity. Transistors Q17 and Q21 are Z8.
part of the AGC circuit. The position of the jumper link
JP7 to either SK10 or SK11 determines from which point In normal use the mute inside Z8 is enabled in three other
the AGC circuit is triggered. The default is for the jumper ways:
to be fitted to SK10 which minimizes cross modulation
and prevents the IF amp becoming saturated. The AMUTE signal from the micro controller is active at
power-on and for a short time when a preset is changed.
The LA1266 (Z9) demodulates the IF at pin 1 into an When the band is changed the output is muted by charging
audio output at pin 12. The quadrature coil is a C52.
double-tuned device for best distortion performance. The audio output must be muted whenever the tuner is in
stereo mode and is also off-tune. This is to eliminate noise
When a station is tuned correctly the 'On Tune' signal goes during tuning and is provided by Q8 and the MONO and
low and drives a green LED on the display PCB. This OFF TUNE control signals.
signal is also used by the auto-stop detection and muting In Mono mode this mute is disabled so that weak stations
circuits. can be heard, despite the noise.
AM Tuner & IF Micro controller
The LA1266 (Z9) contains the AM RF amplifier, oscillator Control of the DiVA T51 tuner is performed by a single
and mixer circuitry. micro controller Z10, LA7230. This also provides keypad
input and drives a LCD directly.
Switching between FM and AM modes is controlled by the
'FM' signal from the micro controller which disables the At power-on a matrix of diodes is scanned to set-up the
AM circuitry of Z9 and switches the path of the audio controller for the correct options:
signal through Z8.
D7 selects the correct frequency ranges.
MW/LW switching is performed by switching transistors
Q12, Q14 & Q15. D10 enables the use of Auto tuning as well as manual
Each band has its own oscillator and aerial tuning coils, tuning.
tuned by a varicap diode all contained within the AM
module L5. D8 allows the Auto-tuning mode to use the `IF Count'
method of searching.
The 450kHz IF signal is filtered by coil and ceramic filter
combination T5. The position of jumpers JP 5 & JP6 fitted to SK9 are used
to disable or enable LW and also whether the AM band
steps are 9 kHz (UK) or 10 kHz (USA).
Birdie Filter
Z10 provides control signal outputs for the following
The `Birdie Filter' (L2) is a four pole low pass filter, flat to functions:
about 53kHz, then with a very steep roll off from then on..
This is designed to reduce co-channel interference in FM MONO - To defeat the stereo decoder
Stereo and cut down on irritating `birdie' noises.
AMUTE - Turns on the mute circuit when a button is
pressed & during tuning.
FM, MW & LW - Only one output active low at any one
time. Used to switch on specific parts of the RF circuitry as
appropriate.
The micro controller includes a Phase-Locked-Loop (PLL)
circuit which compares the tuner local oscillator signals
(FMIN & AMIN) with a reference frequency. Based on
this information and the required tuned frequency the
controller varies the tuning voltage to the FM and AM
front ends.
The tuning voltages (FMVt & AMVt) have to be filtered
from the PLL by the circuitry around Q7 & Q13.
Display PCB
The display PCB holds the keypad, LCD display, LED
back light module and On-Tune indicator.
The remote control receiver consists of the receiver RX1
and the PIC micro controller, Z1, which is used to decode
the incoming remote control codes from RC5 format to
Sanyo type commands. This is because the Sanyo micro
controller, Z10, can only respond to Sanyo remote control
commands.
Jumper Settings
Jumper Option 1 Option 2
JP1 Best sensitivity Best sound
JP2 Best sensitivity Best sound
JP3 De-emphasis 50uS De-emphasis
75uS
JP4 De-emphasis 50uS De-emphasis
75uS
JP5 LW & MW MW only
JP6 AM spacing 9KHz AM spacing
10KHz
JP7 Less X-MOD Less De-sense
USA / Rest of the World
If the T51 is transferred from or to the USA the
following jumper settings will require changing.
Jumper Rest of the USA Action
World
JP3 50uS 75uS De-emphasis
JP4 50uS 75uS De-emphasis
JP6 9KHz 10KHz AM spacing
1 2 3 4 5 6 7 8
LK31 LK41 LK51
LK22 LK32 LK52
LK23 LK33 LK43 LK53
LK24 LK34 LK44 LK54
D D
LK25 LK35 LK45 LK55
LK26 LK36 LK46 LK56
LK27 LK37 LK47 LK57
LK18 LK28 LK38 LK48 LK58
LK19 LK29 LK39 LK49 LK59
LK20 LK30 LK40 LK50 LK60
C C
FM/AM IF Demodulator Stereo decoder and Audio
L892C2_1_2.SCH L892C3_1_2.SCH
LCTR AM Audio AM Audio
HCTR FM Audio FM Audio
IFCNT
LO OFF TUNE OFF TUNE AMUTE
Power Mute Power Mute
SD MONO
AMIN FM FM STEREO
SCAN LW PICMUTE
EL1 PS DD4
AMVt ON TUNE PCB MATERIAL
Update Box Photo Strip
FMVt CEM1, 2 OZ Cu
UPDATE_BOX PHOTO_STRIP CEM1_20Z
Microprocessor and PLL
Photo Block
L892C4_1_2.SCH
FMVt ON TUNE Tooling & Fixing Holes PHOTO_BLOCK
AMVt
LW Tooling Holes Main PCB Fixing Holes
SCAN FM
PD1 PD3
AMIN MW
B TOOLING TOOLING B
SD FIX5 FIX1 FIX2 FIX3 FIX4
PICMUTE
STEREO
LO MONO
PD2 PD4
IFCNT FIX6 FIX7 FIX8
TOOLING TOOLING
HCTR AMUTE
LCTR
F3 EL10 DD1 DD2 DD3
Cable Drilling A2 Vertical A2 Horizontal
Tie Detail Paper Marker Paper Marker
CABLE_TIE DRILL_DWG DD_A2V DD_A2H
T100MASP
Kit Mask
Exclude 'NF' parts from kit mask, i.e. Not Fitted.
This applies to R4 and R104
PCB L892PB_1
PCB
DRAWING TITLE
A A
T51 Tuner
Circuit Diagram
Notes: 1.2
00_1078 CL 12/09/00 R93 WAS 220R NOW 1K0
A & R Cambridge Ltd.
Pembroke Avenue 00-1044 CL 17/7/00 PRODUCTION RELEASE 1
Denny Industrial Centre
ECO No. INITIALS DATE DESCRIPTION OF CHANGE ISSUE
Waterbeach Drawn by:
Cambridge CB5 9PB Filename Date Printed
Sheet 1 of 4
G:\DATA\ECO\ECO AGENDA\00_1078 L892 T51 TUNER\L892_1\L892_1.ddb - L892c1_1_2.prj12-Sep-2000 CL DRAWING NO. L892CT
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8
P12V
Q3 R38
BC557B 4K7 MF
R29 R37 Low = AM
10K MF
AMVt 4K7 MF
F Q11 R40
C27 R53 C34 T5 AM_IFT BC547B FM
D 100K MF D
A_AMVT 100N PC 100K MF 10P CD
A_AMSIG3 R58
R44 100K MF
68K MF
C54 R16 C50 C49
1U0 EL 22K MF 47N CD 47N CD
L5
AM_MODULE A_AMSIG2
1
6A 1A 6C 1C
5A 2A 2C C47 C22 + C48
2 47N CD 10U EL 47N CD
22K MF
+
R78
4A 3A 4C 3C C53
+ 1U0 EL
6B 1B 3D 4D
3
R52
22K MF
TP6
R55
R79 22R MF
2B 2D 5D A_AMAUD
5K1 MF R69 C26
A_SMETER 18K MF
4B 3B 1D 6D C65 1N0 CD
AM Audio
+
AMIN
7
4
6
5
9
8
Cans 1U0 EL
24
23
22
21
20
19
18
17
16
15
14
13
IFCNT
TP7
A_AMLO
680P PP
47K MF
7
4
6
5
9
8
C66
P12V
R84
R77
Reg
AGC
Osc
AM O/P
STRQ
AM Osc
IF out
AM I/P
AM adj
IF in
S meter
Z9
SCAN 15K MF
A_AMSIG1 LA1266
C C
R87
Mount Close to L3 TP9
4K7 MF Q12
On Tune
R28
1K2 MF
FM O/P
Quad 1
Quad 2
BC547B FMCENTRE
FM I/P
AM IF
2K7 MF C71
FM IF
R72
GND
AFC
Vcc
D27 + C23
10U EL 1N3 PP
1
2
3
4
5
6
7
8
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