[Amps] AL-80A - Won't tune on 160m.

[George Hall]

Greetings Bill and the group,

I have a late model AL-80A build in mid 1989 just a few months before MFJ bought Ameritron and soon after replaced the AL-80A with a total redesigned AL-80B which is still in current production with some change along the way.  According to Carl KM1H On Nov. 28, 2015 QRZ.COM AMPS Forum the band switch wafer that usually burns out is the 160m contact solder terminal.  To prevent this from occurring a #8 brass flat washer is placed over the 160m terminal and soldered in place (see attached photo with yellow highlight and red circle area - sorry for the photo of a black and white picture ... that’s all I have and I don’t remember where I downloaded it from).

My AL-80A had this #8 brass flat washer installed as Carl said, but I have a feeling earlier production AL-80A models did not.

However you replace the burnt 160m band switch contact, if you AL-80A does not have this brass flat washer in place, then I strongly suggest you do so.

73, George  N2CG   
 

-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Bill Coleman
Sent: Saturday, September 03, 2016 12:11 AM
To: Amps Reflector
Subject: Re: [Amps] AL-80A - Won't tune on 160m.


> On Jun 22, 2016, at 6:56 PM, Bill Coleman <aa4lr at arrl.net> wrote:
> 
> I managed to fix my issues with the metering circuits on the AL-80A. However, while it appears to work correctly on 80-10m, I cannot get the output network circuit to resonate on 160m.
> 
> I hooked it up to a dummy load, fed about 35 watts, keyed and tune. Peak output is achieved at maximum C for both Plate and Load, but it’s only maybe 100 watts out, and the tuning is very broad. Nothing like 80m, which works fine.
> 
> Any suggestions?

I finally got the AL-80A on the bench again and found that the switch contacts for the extra plate circuit capacitance are burnt away. Since I’ve never used the amp on 160m, this wasn’t me, but probably the previous owner.

So, this problem is at least identified. I’ll have to either replace the contacts, or the entire switch wafer.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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