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

)
SECTION III
MAINTENANCE
3 -1
COVER REMOVAL
You will be able to slide the one-piece cover off of the instrument
after removing the four screws in the rear of the cover.
3-2 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 checker". The res ults obtained from the "tube
checker" can be misleading. Mark original tubes to insure return
to the same socket. Replace only tubes proved to be weak or de-
fective.
Any tube with corresponding standard EIA (JEDEC) characteristics
can be used as a replacement.
3-3 POWER SUPPLY
Rectifier CRI is connected in a half-wave circuit. The dc output
voltage between ground and the junction of C96 and L25 should be
11 0 ±:lO volts with the line voltage set to 115 volts. The GAIN
control should be set fully clockwise to maximum. Ripple voltage
can be quite high without affecting instrument performance.
Low power supply voltages are generally due to a weak selenium
rectifier, leaky filter capacitors, shorted tubes or off value plate
line, grid line, or screen resistors.
3-4 230 VOLT OPERATION
The
r$fJ
Model 460AR can be quickly and easily converted to operate
from a nominal 230 volt 50/1000 cps power source. The instrument
is normally supplied with the dual primary windings of the power
transformer connected in parallel for 115 volt operation. To con-
vert for 230 volt operation, reconnect the primary windings in series
as shown on the schematic diagram. The line fuse F I must also
be changed from O. 6 amp. slow-blow to 0.4 amp. slow-blow.
-7-