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Maintenance; Cover Removal; Tube Replacements; Power Supply - HP 460BR Operating And Servicing Manual

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SECTION IV
MAINTENANCE
4-1
4-2
4-3
COVER REMOVAL
You will be able to slide the one-piece cover off the instrument
a f t e r removing the four s c r e w s i n the r e a r of the cover.
TUBE REPLACEMENTS
In many c a s e s instrument malfunction can be c o r r e c t e d by replac-
ing a weak o r defective tube.
ment o r component replacement, check the tubes.
Adjustments
made in a n attempt to compensate for a defective tube w i l l often
complicate the r e p a i r problem.
Before making any internal adjust-
It is good practice to check tubes by substitution r a t h e r than by
the use of a "tube checkert1. The results obtained from the "tube
checker" can be misleading.
Mark original tubes to insure r e -
t u r n to the s a m e socket.
defective
Replace only tubes proved to be weak o r
Any tube with corresponding standard E E I A (JEDEC) c h a r a c t e r i s t i c s
can be used as a replacement.
POWER SUPPLY
The 460B power supply delivers two output voltages depending
upon the setting of PULSE-LINEAR switch S1.
With S1 i n the PULSE position, selenium r e c t i f i e r s CR-1 and CR-2
a r e connected in a voltage doubler circuit.
The dc output voltage
between ground and the common junction of capacitor C22, filter
choke L28, and fuse
F2
with the line voltage s e t to 115 volts will
be 270
&
15 volts.
ing instrument performance.
Ripple voltage can be quite high without affect-
When switch S1 is in the LINEAR position, r e c t i f i e r s CR-1 and
CR-2 a r e connected in parallel a s half-wave rectifiers.
The dc
output voltage between ground and the point described above w i l l
be 110 volts when the line voltage is s e t to
115
volts.
Ripple volt-
age is again not critical.
Low power supply voltages a r e generally caused by weak selenium
r e c t i f i e r s , leaky filter capacitors, shorted tubes o r off-value r e -
s
is t o r s
.
-9-

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