Alpha 9500 HF Linear Amplifier Operating Manual Alpha Radio Products
Diagnosing Faults Product Release 1
DOCNUMBER 9500
Document Issue 1, Revision 7
Page 9–8 June 2009
99
Resolution 1. Unplug the amplifier, wait 30 seconds, and plug it back ON to the
ON2 or ON/AMP setting.
2. Even if the last fault is still fault 10, attempt to turn the load capacitor
from the buttons on the front panel or from the AR9500 PC
application. If the capacitor responds, the fault may have cleared.
3. If the fault persists, contact ALPHA technical support. If possible,
send them the contents of the fault log. To display the fault log, from
the AR9500 PC application, open the Fault window and select Tools
> Get fault log.
Fault code 11
Description Over-temperature.
Explanation The amplifier has a built-in temperature sensor to ensure that the tube
does not overheat. The sensor is located on the cathode board, in the tube
deck compartment. Air from the blower motor impinges on this board and
then flows up through the tube anode fins. Normally the temperature it
reports is at approximately this air temperature. Since the air has already
been drawn over other parts of the amplifier, it is some 10–20C warmer
than ambient air. The trip value is currently set to 50C.
The amplifier goes to ON AMP, but in bypass mode and with the tube
biased off. This should reduce plate dissipation to a minimum and, if the
air system is working correctly, the temperature should start to fall. When
it reaches a safe value, the amplifier can be put in service again, as
indicated by fault code 13 (clear temperature).
Resolution 1. Ensure that there is air exiting the amplifier from the hexagonal
pattern of holes near the rear left. If not, this is likely the cause.
2. If there is no air leaving the amplifier when it is in the ON AMP
position, assuming that all other front panel displays appear normal,
ensure that there is nothing obstructing the air flow at the inlet (on the
right rear of the amplifier) or at the exit.
3. Ensure that the external fan is operating. The fan is at the right rear of
the amplifier, covered by a wire grill. It should start to rotate in the
ON AMP condition. Use a flashlight if necessary to avoid the
appearance of nonrotation due to the stroboscopic effect. This can be
done without removing the amplifier cover.
4. Check the internal airways of the amplifier. Unplug the amplifier,
remove the cover, and ensure that the blower motor (to the right of the
tube) is clean and that its impeller rotates when moved gently with a
long screwdriver. Look down into the tube and ensure that the
passages between the anode fins are not blocked, for example by an
accumulation of dust.
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