[Amps] Alpha 87A Won't Key

[Charlie Young]

Frank, the amp should go to operate mode after the warm up delay if you push the mode switch to operate.

It should go to operate mode regardless if the amp is keyed or not.  It won’t go to operate mode unit the timer interval is up.



When it is in operate mode but not keyed, it is feeding through the antenna to the receiver through the pin diodes. When you close the keying circuit , the pin diodes switch the amplifier to transmit mode.  If it won’t go into operate mode the amp won’t key to transmit.



There are a number of things which will keep the amp from going to  operate mode when the mode switch is changed from standby to operate.



The amp must be in operate mode before closing the input keying line will do anything.  If it is not going into operating mode, there is some other issue.



That no faults are showing is a good thing.



The 87A is known for having contact resistance issues on the molex pins which connect the wiring harness to  the various boards.   This is a very common problem.  I would start by opening up the amp and unplugging each of these

plugs and reinserting it on the male pins a few times.   A bit of Deoxit spray on each connection might help.



73 Charlie N8RR







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________________________________
From: Amps <amps-bounces at contesting.com> on behalf of Frank Kirschner <frank.kirschner at gmail.com>
Sent: Wednesday, November 22, 2017 4:28:37 PM
To: amps at contesting.com
Subject: [Amps] Alpha 87A Won't Key

The Alpha 87A I got in the ARRL auction won't key up.

I connected to the RS-232 port satisfactorily, and it showed no faults.  I
have the transceiver RF out connected to the RF input of the amp, the RF
output of the amp connected to an antenna (TH-11), and a relay connected to
the keying relay input.

I checked the relay input, and it does short to ground when the transceiver
goes to transmit.  But the amp stays on SDBY, and the OPR light doesn't
come on.

Is there something I just don't know to do?  I've never used a
microprocessor-controlled amp before, so there may be a trick to it.

I'm on 20 meters, so I assume it isn't a 12-10 meter lock-out thing.

Thanks.

73,
Frank
KF6E
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