SECTION IV
MAINTENANCE
4-1 COVER REMOVAL
You will be able to slide the one-piece cover off the instrument
after removing the four screws in the rear of the cover.
4-2 TUBE REPLACEMENTS
In many cases instrument malfunction can be corrected by replac-
ing a weak or defective tube. Before making any internal adjust-
ment or component replacement, check the tubes. Adjustments
made in an attempt to compensate for a defective tube will often
complicate the repair problem.
It is good practice to check tubes by substitution rather than by
the use of a "tube checkert1. The results obtained from the "tube
checker" can be misleading. Mark original tubes to insure re-
turn to the same socket. Replace only tubes proved to be weak or
defective
Any tube with corresponding standard EEIA (JEDEC) characteristics
can be used as a replacement.
4-3 POWER SUPPLY
The 460B power supply delivers two output voltages depending
upon the setting of PULSE-LINEAR switch S1.
With S1 in the PULSE position, selenium rectifiers CR-1 and CR-2
are 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 set to 115 volts will
be 270 & 15 volts. Ripple voltage can be quite high without affect-
ing instrument performance.
When switch S1 is in the LINEAR position, rectifiers CR-1 and
CR-2 are connected in parallel as half-wave rectifiers. The dc
output voltage between ground and the point described above will
be 110 volts when the line voltage is set to 115 volts. Ripple volt-
age is again not critical.
Low power supply voltages are generally caused by weak selenium
rectifiers, leaky filter capacitors, shorted tubes or off-value re-
s is tor s .
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ACEC
HEWLETT-PACKARD
