[SCCC] Alpha Repair

[Bill Kendrick]

Hi John

 

Fault 1 relates to the PIN diode bias. It is an indication that there is not
enough back bias on the receive diode.

 

I took apart the amplifier and reseated the molex connectors in the pin
switch box as well as all the connectors I could get my hands on. I closed
everything up. 

 

Before I opened up the amp, when I used the footswitch to key the amp it
would hard fault to Fault 1 even with no RF power applied.  After I closed
the amplifier up I turned it on. There was no antenna or transceiver
connected. It stood alone. Initially it showed a fault but it cleared after
warm up. I manually shorted out the relay input using a plug on the end of
the RCA control cable that normally goes to the transceiver to switch the
amplifier. It switched and there was no fault. Perhaps I fixed the problem.

 

The problem could be in the transceiver. If the switching transistor is
failing possibly the relay input is not pulled completely to ground and the
bias is affected. I will next reconnect the transceiver and antenna. I will
manually switch the amplifier to transmit and drive it with a little bit of
RF. If that works I will reconnect the relay control cable to the
transceiver and try to repeat the failure. If the amp works in this
configuration then it was a corroded or unseated molex connector. One
connector was not fully seated and may have been the problem or I did scrape
enough oxidation off by removing and then reinstalling the connectors that
there is enough continuity.

 

I am going to finish the check out tomorrow and I will let you know if the
connector reseating did the trick or if the problem is in the radio.
Hopefully the problem is now gone. I really do not want to crack open the
radio and replace the switching transistor.

 

Bill

N6RV

 

 

  _____  

From: John Stanford [mailto:wb8svn at gmail.com] 
Sent: Thursday, April 13, 2017 5:03 PM
To: Michael S. Mitchell W6RW
Cc: Bill Kendrick; sccc at contesting.com
Subject: Re: [SCCC] Alpha Repair

 

Hi Mike, Bill,

 

I recently repaired an Alpha 87A amplifier for Larry A. Mallek, K6YUI,
lmallek at roadrunner.com <mailto:lmallek at roadrunner.com> .

 

His 87A had a similar problem which required a soft fault and hard fault
reset before diagnostics could proceed. Ended up being a bad tube.  So I'm
all set up to reset the faults. 

 

Other Alpha amps repaired include an Alpha 91b, Acom 2000A (sim to 87),
Mike's Alpha 77 and several Alpha 76A's and 78's.





John, KF6I

Sent from my iPhone


On Apr 13, 2017, at 12:04 PM, Michael S. Mitchell W6RW <w6rw at earthlink.net>
wrote:

I use John Stanford KF6I for all of my amplifier repairs. He is especially
good with Alphas. He has made and has on hand new front panels for many
Alpha models and has repaired my 77SX with extremely good results. He lives
in Placentia in Orange County and his mobile phone number is (714) 412-7399.
I highly recommend his services.


-----Original Message-----



From: Bill Kendrick <kendrick.w at ca.rr.com>

Sent: Apr 13, 2017 10:56 AM

To: sccc at contesting.com

Subject: [SCCC] Alpha Repair

 

Is there anyone in the LA area who repairs Alpha 87a amplifiers? My

amplifier just hard faulted (Fault 1). It was one of W6EENs amplifiers and

needs some maintenance as well.

 

 

 

Bill

 

N6RV

 

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