Table of Contents
Advertisement
HP 8110 Α Service Guide
4-1 0
T
r
oubles
h
ooti
n
g
ι
Ι
Ι ~
25 μ 5
~ Ι
Ι
14 μ5
ι
DERIVED
F
ROM 150 V AC
280V DC
AT OSCILLATOR
F
REOUENCY
O
F
71 1Wz
D
ERIVED
FROM 240 VAC
380V DC
AT OSCILLATOR
~ENCY OF
F
igure 4-6.
W
aveforms at C
R
407 a
n
ode
If
t
here are no waveforms, and LED s DS401 and
D
S402 ( Figure 4-4)
are not illumin ated, ch eck at CR401+ for 100 V - 360 V
D
C,
dep en ding on mains inpu t voltage. If this voltage is
p
rese nt, switch
t h e power OFF
a
n d per form cont inui ty ch ecks on FET s Q404 and
Q405, plu s
f
or ward a nd reverse res istance o f
d
iode C R407 . If th e
FET s read sh ort-c i rcuit they are faulty.
If wave for m s are still n ot there, or are s howing unu s ual behavi our,
s wi tch OFF an d check all di odes (in cluding LED s) in the Prim ary
Section . In
m
ost cases it is sufficient to check the diodes while
sol dered in p osi ti o n , using an imp edance
m
eas ure ment .
Compo n en ts
m
ost lik ely to
b
e
f
aulty in this area are :
ι Q402 -
b
ase/e mitter short
ι
C
R405 - s h ort-ci rcuit
ι Ζ401 - op en
c
ircuit, s hort-ci rcuit, out of sp ec ificat ion
ι
U
401 - out pu t stage faulty
FETs Q404 a n d Q405 are
p
ressed into contact with t he heatsink
using α sp ring clamp .
R
emo ve thi s to replace either de vice. However,
Advertisement
Table of Contents
