Tait T805, Service Manual

Page: 54 / 96

9.14 Fault Finding
M805-00
30/04/95 Copyright TEL
9.4.10 T805 Digital Outputs
260ms
680ms
Observe the signal on pin 19
of IC306. Does it appear similiar
to the waveform below?
Is the DSP OK?
Is the AIC OK?
Y
N
N
Y
260ms
680ms
Is the DSP OK?
Is the AIC OK?
Y
N
N
Y
260ms
680ms
Check for shorts
Is the DSP OK?
Is the AIC OK?
Y
N
N
Y
Observe the signal on pin 15
of IC306. Does it appear similiar
to the waveform below?
Observe the signal on pin 12
of IC306. Does it appear similiar
to the waveform below?
Is the DSP OK?
Is the AIC OK?
Is pin 16 of IC306
at logic 0?
Is the DSP OK?
Is the AIC OK?
Check the watchdog
reset circuitry.
Repair as necessary.
Y
Y
N
Y
N
Y
N
Remove power from the ASP card.
Remove any short from link-1.
Place card in test mode 1 and
apply power.
Check for overheating components
and short circuits.
Repair as necessary.
N
Y
Is the DSP OK?
Is the AIC OK?
Repair as necessary.
Replace IC126.
Is the DIGOUT LED on?
Y
N
N
Y
N
Y
Check Q309, the DIGOUT LED and associated circuitry.
Replace as necessary.
Check R330 and Q311.
Check for shorts.
Repair as necessary.
Y
N
N
Y
Y Is the DSP OK?
Is the AIC OK?
N
N
Y
Are the TSGM, LEM, AIM
and ARM LEDs on?
Is the DSP IS OK?
Is the AIC OK?
Check the appropriate driver
transistors (Q304, Q303, Q302
& Q301) and associated circuitry.
Replace as necessary.
Is the DSP IC OK?
Is the AIC OK?
Check the transistor invertor (Q308),
LED transistor (Q305) and
associated circuitry.
Repair as necessary.
Y
N
Y
Y
N Y
N
Y
N
Change DIP switch settings to test mode 3.
Power down the card and
remove the short on link-1.
Power up the card.
Does only the TEST MODE LED come on?
N
Check for shorts. Replace IC306.
Repair as necessary.
Check for shorts. Replace IC306.
Short link-1.
Is pin 15 at 0V? Check for shorts. Replace IC306.
Repair as necessary.
Is pin 10 of IC126
at 0V?
Is pin 10 of IC307
at logic 1(>3V)?
Replace IC307.
Replace IC306.
Repair as necessary.
N
Is pin 8 of IC313 at 0V? Is pin 12 of IC306 at 0V? Replace IC313.
Replace IC306.
Is pin 8 of IC126 at 0V?
Is voltage on pin 19 of
IC306 >3V?
Replace IC306.
Repair as necessary.
Replace IC306.
Repair as necessary.
Check pins 2, 5, 6 & 9 of IC306.
Are they all at 0V?
Replace IC306.
Repair as necessary.
Digital outputs are OK.
Repair as necessary.
Replace IC306.
Repair as necessary.
Place a pull-up resistor between
the DIGOUT output and 13.8V supply.
Is the DIGOUT output at 0V?
Check the voltage on
pins 2, 5, 6 & 9 of IC306.
Are they all >3V?