HP 4262A - Page 234

PROCEDURE: 1
|Either
Set
4262A
controls
as
follows:
i
Monitor
signal
at
A14U10
pin
3
AHemately
press
120Hz
Altemately
press
120Hz
pmn 3. jor OK?
START
~——]
o
gl
ot
M4TP4a
INO
Is
waveforms
for
each
test
fre.
»{
and
1kdiz
buttons.
Does
(MO
|
and
1kHz
buttons.
Does
[NO
Check
A14Q11.
.
FUNCTION.
.............
C
squarewave?
quency
as
illustrated?
the
dc
level
at
A14Q10
the
dc
level
at
A14Q11
CIRCUITMODE.
......
PRL
Collector
change
between
Collector
change
between
LCRRANGE
.......
AUTO
YES
TEST
Waveform
5V
and
-12V?
.
5V
and
0V?
TRIGGER.
............
INT
r
Unknown
.......
Open(0pF)
SIGNAL
at
U0
pin
3
YES
YES
Observe waveforms at A14TP5
and
TP4.
Do
they
have
precisely
.
5
the
same
phase
as
each
other
for
Issvs;)gnpa;:l?;efil‘}UQ
pin3
NO
»
Check
A14Q8.
-
all
test
frequencies
(120,
1k
and
-
’
10KH2)?
Ses
photo
below.
2V/div.
50us/div.
Check
A14Q9
and
CR13.
Check
A14Q10
and
CR14.
YES
4
A14TP4
»
)
2V/div, 10us/div.
Is
potential
difference
be-
NEO
Both
and
A14TP5
tween
A14Q7
B;:se
and
Check
A14Q7.
NO
®
Set
TEST
SIGNAL
to
NO
Is
signal
at
A14U14
pin
6
YES
Emitter
0.6Vdc?
1kHz.
Issignal
at
A14U15
a
pulsed
waveform
with
a
Check
A14U15.
pin
12
square
and
4kHz?
duty
factor
of
1/3
at
40kHz?
YES
Is
de
voltage
at
A14U10
YES
NO
pins 4 and 8 at 5V?
YES NO
Monitor
signals
at
A14Q19
and
Check
A14U9.
l
?gfifs'{ssffiqb::;{;;oof
NO
?(I)t]:hma}t:]a
presle
kHzmand
NO
22
Gates.
Do
they
look
like
2.
I
z
buttons.
Does
the
thir
Y
the
signal
at
A14U15
pin
12
de
level
at
AT4US
pin
3
Check
A14U8.
Check
A14U10
1kHz?
change
between
high
and
and
CR9
through
Check
A14CR23.
low
level?
CR12,
YES
@)
Q19
Gate
YES
Symptom
Check
Result
Q22
Gate
4
NO
|
AndQ
_
Set
TEST
SIGNAL
to
.
NO
|
Can
a
pulsed
waveform
be
observed
®
Symptom
|
Check
vlv’;];’:f'orl;ao‘;';?;:g‘::’e
NO
Check
A14U14,
5V/div
at
A14U8
pin
11?
A14U14
pin
8?
YES
@
YES
Al14Q21
pimn
&7
NO
Is
dec
level
at
A14Q21
(Q24)
YE:
@
Emitter
3V?
@
NO
Al4UB
s
@
YES
Al4U11
Monitor
signal
at
A14Q6
Collector.
NO
A14CR21
@
Is
the
waveform
as
illustrated?
Check
A14U12.
Does the signal frequency
satisfy the table below?
A14Q6
@NO
|
Is
amplitude
of
the
pulse
k/‘JO
Does
4Vp-p
square
pulse
|{NO
Check
A14U13
Collector
at
A14Q6
Collector
15Vp-p?
appear
at
A14U13
pin
67
ec
:
TEST
SIGNAL
Frequency
YES
YES
1
120Hz
120Hz
(8.3ms)
|
1kHz
1kHz
(1ms)
]
Monitor signal at A14U8
10KHz
1kHz
(1ms)
pin
8.
Is
the
pulse
width
Do
avPp
pulse
appearat
[NO
Check
A14US.
10us?
P
-
YES
.
~
YES
NO
YES
Go to PROCEDURE 2
NO
Check
A14U13.
Check
A14US,
Check
A14Q6
and
CRS.
Figure
8-39.
A14
Phase
Detector
&
Integrator
Board
Troubleshooting
Tree
(A).