Hi Ed,
I had the exact same problem a few years ago with my AL-1500. Check that
the machine screws that support the HV diode board through the bottom of the
amp case are good and tight. The diode board apparently grounds via the
aluminum standoffs. Mine were just a little loose and the contact
resistance was just enough to allow the HV to float up a bit - which was
causing the grid meter to read a negative current. Tightening the screws
corrected the problem.
Hope this help you.
73
Matt
KM5VI
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Edward Seeliger
Sent: Saturday, December 13, 2014 9:52 PM
To: amps@contesting.com
Subject: [Amps] Ameritron AL1500 help
I have an Ameritron AL1500 in which I have replaced the QSK board. After
replacement, the amp appears to work as it should EXCEPT that the grid
current meter reads backwards (deflects down). I can key the amp with
increasing drive and get increasing output (I did not move the tuning
controls when I replaced the board and it tunes/loads as it should).
I have verified all my connections are correct to the QSK board and all
resistance measurements are as specified in the QSK board documentation. I
have spoken to Ameritron twice - the last time they suggested to check the
grounds to the QSK board - I have tightened the screws holding the board to
the pillars that support it above the capacitor bank and resoldered the coax
grounds to the board. They also suggested to check that the blue wire behind
the power on switch attached to the terminal strip the fan wires attach to
is grounded - I tightened that screw also.
But the meter still reads backwards (deflects down).
Have any of you had a similar problem - any suggestions as to what else to
look for/fix.
Thanks in advance for any and all help!
Have a great Holiday season!
Edd - KD5M
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