[Amps] AL-80A - Grid Meter Replacement

[Bill Coleman]

OK, I’ve got an AL-80A that works pretty well. Last April, I was tuning up on 17m and I heard a SNAP, and suddenly the meters read all wacky. The Grid current meter would pin when keyed, and the plate meter was clearly off as well.

Long story short, I finally took the meter board out yesterday, and the 1.5 ohm 3 watt grid shunt resistor clearly took a transient and failed open. That’s the reason for the funny meter readings. 

I’ve got a good handle on that fix, and also adding a protective diode as outlined by W8JI in order to prevent future failures.

NOW, to my question. Even though the meters were all wacky, I, like an idiot continued to USE my amplifier on occasion. Yes, with a little practice, I could safely tune it up even without working meters. Eventually, the pinning of the grid current meter, caused the needle to bend off.

How can I replace this meter? Ameritron doesn’t carry the AL-80A part any more, and the AL-80B uses a different cross-needle meter that won’t work. However, I see that the AL-572, the AL-811, the AL-82 and the AL-1200 all appear to use very similar metering circuits, and single-needle grid current meters. It could be that the meter movement is exactly the same, it just has different scales.

Does anyone know if any or all of these units can replace the Grid Current meter in an AL-80A??

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