Power-Up Routine - Philips PM3055 Service Manual

1 4- 1 0
- Re s i stors .
Can be checked with an ohmme ter after having unso ldered one side o f
the r e s i s tor from the pcb.
and tolerance indicated in the par t s l i s t .
- Coi l s and trans former s .
ohmme ter can be used for trac ing an open c i r c ui t .
An
part ial ly shorted windings can be found by checking the wave form
responses when HF signals are pas sed through the circuit . A l s o an
inductance meter can be u s e d �
- Data latche s .
T o measure on input s and outputs o f data latches a measuring
o s c i l l osc ope can be tr iggered by the c l ock s ignal wh ich is connected
to the c l ock input of the data l a t c h ,
Thi s measurement can only b e made i n t h i s way when there i s an
acceptable repe t i t ion t ime o f the c lock s ignal . A too low c lock pulse
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repe t i t ion t ime results in a low intensity of the trace on the
measuring o sc i l lo s c ope screen.
The outputs can e a s i l y be checked by a vo l tmeter or o s c i l l oscope ,
1 4 . 5 . 3

Power-up routine

Every t ime the instrument is switched-on the f o l l owing ini t i a l i s a t ion
program is executed :
- Resetting the IIC-bu s .
- Re s e t ting D2603
- Determinig the SLAVE-address o f D2603 .
- Checking i f Service rout ine i s required ( i f yes the program w i l l
cont inue with the service ·routine)
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- Checking the "WATCH-DOG" on A7
wil l be lighting for about 1 sec ) ,
- Eventually ini t i a l isation o f the IEEE-opt io n ,
I f during the progr am-run a c ircuit i s found t o b e faul t y ,
s top s . It is rec ommended to switch-off and after a few seconds
switch-on again,
automat ical l y .
'�
again, the fo l l owing procedure indicates how to hand l e . I f no faulure
is found,
sec ond . After this the normal program i s executed .
PROCEDURE :
Check the SDA and SCL line s' after haved switched-on.
c l o ck-pulse
( l ooks like a random pulse ) .
you can localize on what unit the fault exi s t s . This can be done by
f i r s t unplug connector Xl009 or X2001 on re s p , Al and A2 . To localize
what serial-paral l e l conver s ion IC is de fe c t ive , you can disconnec t
the solder j oint in the SDA and SCL print track lead to that I C .
The fol l owing iC ' s can di sconnected in this way:
D2603 , D40Ul , D4002 , D44 0 1 .
When the instrument restar t s every t ime again, this means the WATCHDOG
i s initiating the. main program ( see a l so section 1 0 . 1 . 4 ) ,
can be d i s ab l ed , Thi s can be done by means of the solder j o int j umper
on the rear of the
When d i s ab l ed , pin. l 3 of the microcomputer i s s e t to a low leve l .
Compare the measured value with the value
0200)
( OQ
This wi l l reset the micro-computer controlled sys tem
If the . instrument goes in the same faulty s i tuation
a l l r e levant LeD-segment s wil l be l ighting for about one
mus t be pre s e n t , whi l e the SDA gives the data-information
front unit
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( i f HIGH, a l l r e levant LCD-segments
If one of these signals
p . c . b . (near X700 1 ) .
Shorted or .
the program
the SCL a
On
i s not present ,
DlOO l , Dl lOl , D2602 ,
the watchdog
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