B5.16
T865 Fault Finding
M860-00-Preliminary
30/06/98
Copyright TEL
5.7.4
Noise Mute
Apply on channel signal
@ -117dBm* to receiver.
Refer to audio
fault finding chart.
Ensure PL250 is set
for noise mute operation.
Audio on
IC350 pin 7?
Noise on
IC390 pin 7?
Amplified noise
on C395?
Check Q340
& Q350.
Check D310 is
rectifying noise.
Vary RF level &
observe voltage
on pad 236.
Pad 236 voltage
varies 0-1.8V?
Check 9V rail &
resistors R264,
R265 & R284.
Replace IC270.
Check/replace
IC270 & D240.
Replace Q250.
N
Y
N
Y
N
Y
Y
N
Y
Y
Y
Y
N
Refer to
receiver fault
finding chart.
Check components
around active filter.
Mutable audio
on outputs?
Y
Voltage varies
0-2.5V?
N
OK
Does "Gate" LED
toggle on/off?
N
Check Q230, Q245 &
Q290 for operation.
Y
Adjust RV230
(gating sensitivity)
& observe voltage
on IC270 pin 3.
Set RF signal level to
-117dBm. Rotate
RV230 c/w & cc/w.
Monitor voltage on
IC270 pin 1. Switching
0-8V as RV230 rotated?
Monitor voltage on
IC270 pin 7. Switching
0-8V as RV230 rotated?
Monitor voltage on
pad 234. Switching
0-8V as RV230 rotated?
N
N
N
Does "Gate"
LED toggle?
Check/replace
Q255 & D250.
Y
Y
N
Check RV330
adjustment
(noise mute gain).
Approx. 0.6V DC rect-
ified noise on pad 236?
N
Switch SW201 (monitor
mute) to ensure
mute is enabled.
Rotate RV230
(gating sensitivity)
c/w & cc/w & view
"Gate" LED.
Note:
c/w = clockwise
cc/w = counterclockwise
or anticlockwise
*Modulated by 1kHz signal with
3kHz (2.4kHz) [1.5kHz] deviation.
Содержание T860 Series II
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Страница 32: ...B2 2 T865 Circuit Operation M860 00 Preliminary 30 06 98 Copyright TEL...
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Страница 56: ...B3 14 T865 Initial Tuning Adjustment M860 00 Preliminary 30 06 98 Copyright TEL...
Страница 58: ...B4 2 T865 Functional Testing M860 00 Preliminary 30 06 98 Copyright TEL...
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Страница 86: ...B6 2 T865 PCB Information M860 00 Preliminary 30 06 98 Copyright TEL...
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Страница 110: ...T865 Preliminary PCB Information T865 Grid Reference Index Page B6 26...
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Страница 156: ...C5 2 T867 Fault Finding M860 00 Preliminary 30 06 98 Copyright TEL Figure Title Page 5 1 RF Diode Probe Circuit 5 5...
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Страница 233: ...M860 00 Preliminary T869 Fault Finding D4 5 Copyright TEL 30 06 98 replace A4 pages D4 5 D4 6 with A3 pages D4 5 D4 6...
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Страница 256: ...EII M860 00 Preliminary 30 06 98 Copyright TEL...
Страница 258: ...E1 2 T860 VCO PCB Information M860 00 Preliminary 30 06 98 Copyright TEL...