User's Manual

ALPHA 9500 Interim OPERATING MANUAL

www.alpharadioproducts.com

operator can switch between the dummy load and the antenna at the ﬂip of a switch.

6.3.3 Grid Current Information

The ALPHA 9500 operates in Class AB2 when delivering maximum output power consistent with

excellent linearity. A small amount of grid current ﬂows which can be monitored via the grid current bar

graph. As overdrive approaches, grid current increases rapidly and the red grid LEDs will be illuminated.

At maximum output and efﬁciency, the red grid LED lights should not be illuminated. If the red LEDs in

the bar graph light up before the desired value of plate current and/or power output is reached, readjust

ampliﬁer loading before continuing.

6.3.5 Turning On The Ampliﬁer

Please Note: Every time the ALPHA 9500 is powered up there is a built-in warm up wait. This

countdown (in seconds) will be displayed on the seven segment display, and the STBY switch

light will toggle on and off. Depressing any other button that controls the seven segment display

(for example Vp) during the warm up period will show that parameter. The operator can return to

the countdown display by pushing the FLT (Fault) button.

CAUTION:

EXHAUST AIR MUST BE DETECTABLE FROM BOTH TOP VENTS.

If exhaust air is not coming from the top vent, TURN OFF the ampliﬁer immediately and verify that

the exhaust chimney is properly positioned over the tube. When the warm up delay is complete

(about 90 seconds), the STBY switch light will be on steadily. Push the OPR switch and ALPHA

9500 is now “ready”.

While the ampliﬁer is warming up, check the plate voltage reading on the seven segment display.

It should read between 3300 V and 3500 V. If the value is below 3000 V, this indicates a problem

which should be solved before using the ampliﬁer. First check your outlet, the wiring of the plug

and the grounding of the equipment in your shack. If you have somewhat variable or unstable

power, it is possible to “force” the ampliﬁer to always choose a particular tap setting. Please

contact Alpha Radio Products directly for information on how to “force” the tap selection.