Henry Radio 3K Classic Mark II Operating And Maintenance Manual page 18

high voltage lead between the RF section and the power supply. If the short
disappears the problem is in the RF chassis or B- return.
If the problem
persists,
the problem is in the power supply.
If the short is in the RF-
chas-sis or in the B- line, remove the top cover and search for any visible
sign
of a short.
Then use an ohmmeter to trace the circuit from the high
votlage connector to the blocking capacitors, including the tube(s).
If
the
problem is in the power supply you will again have to check for vis-
ible signs of a short, or use an ohmmeter to locate the short. Often how--
ever
a high voltage short will only show when the high voltagp is applied.
To locate such a short it may be necessary to unsolder leads to remove tom_._
ponents from the circuit until the short disappears. Start with the filter
capacitor, move back: to the filter choke, and then the rectifiers. Finally
remove the power transformer from the circuit.
Keep in mind that a high
voltage short may blow the cathode fuse in the RF chassis.
LOW
PLATE
VOLTAGE - This problem is usually an indication of low AC line
voltage.
It can only be solved by retapping the power transformer as des--
cribed in Section 3.4.
HIGH PLATE VOTLAGE -- This problem can be caused by high AC line voltage and
should be brought into specification by retapping the power transformer as
described in Section 3.4.
The problem can also be caused when the filter choke is out of resonance. A
resonated
filter choke is used in the design because of its superb linear--
ity
and voltage regulation.
However,
the choke must be resonated to a
specific AC frequency (50 Hz or 60 Hz) using capacitors.
If the capacitor
fails, or
if
the amplifier was set up at the factory for a different AC
frequency,
the voltage regulation becomes poor. The result will be exces-
sive high voltage when the amplifier is not transmitting and excessive vol-
tage
drop during transmit.
Three .01 mf capacitors are used to resonante
the filter choke for 50 Hz and two are used for 60 Hz.
NO
HIGH
VOLTAGE METER READING - The most likely cause is a blow cathode
fuse in the RF chassis.
After that,
other likely causes are a failure or
value change of the high voltage multiplier resistor in the power supply,
or a failure in the meter circuit.
SECTION 6.6 BLOWER PROBLEMS
These
amplifiers have an airflow switch in the blower which turns the amp-
lifier off to protect the tube in case of blower failure.
Sc' if you find
that
the
amplifier is intermittantly turning off or if the pilot lights
will not come on be sure to check the airflow switch on the blower.
The
blower is one of the most susceptible parts to transportation damage.
Henry amplifiers use squirrel cage blowers because of their exceptional air
blowing capability in a small size.
But the blower assembly can be easily
damaged if the amplifier is dropped during shipment. When the amplifier is
installed
make certain that a strong flow of air is coming out the top of
the amplifier when it is turned on. Other indications of blower damage can
be a resonance in the amplifier cabinet caused by an unbalanced fan, an !rn--
equal
flow of air between the two tubes in the 5K Classic, or mechanical
noise from the blower.
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