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[AMPS] AL-1500 oscillation?

To: <>
Subject: [AMPS] AL-1500 oscillation?
From: (
Date: Sun, 21 Feb 1999 16:16:37 -0500
Arliss, is it an Ohio built Ameritron or an MFJ version?
I believe Sept 1989 was the transition date.

Try that tube in your 6M amp. The steady power signifies a neutralization
problem and can be due to either the tube or the circuit. Has this
occured in the past or is it just recent?

Also check the bias zener since they switch in a 2nd one in the SSB
Finally, check the glitch diode and the 2 tiny 50V bypass caps on the PS
B- rail. A diode short/tube arc often blows the caps apart.

73  Carl  KM1H

On Sun, 21 Feb 1999 09:48:18 +0000 W7XU Arliss <> writes:
>I noticed a problem with my Ameritron AL-1500 amp
>tonight.  When the amp is keyed in the CW position
>with no drive (but with the exciter connected to the
>input of the amp), all seems fine, with no RF out
>and no grid current.
>But if I then switch the mode position of the amp
>from CW to SSB, with no other changes, the grid current
>begins to flow (slowly at first, then more rapidly) 
>and the watt meter indicates about 50 W output.  If the
>feedline is removed from the exciter, the problem 
>persists.  However, if I then short the input, the grid
>current and power out drop to zero.  When the exciter is
>reconnected to the input, the amp takes off again.  This
>happens with the band switch in any position, but becomes
>progressively worse as you go lower in frequency.
>Since it's the weekend I haven't had an opportunity to
>contact Ameritron, but I'm wondering if others have 
>experienced this problem and what was needed to correct it.
>73,  Arliss  W7XU
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