al80a meter replacement

Discussion in 'Amateur Radio Amplifiers' started by N8VUL, Jul 2, 2020.

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  1. N8VUL

    N8VUL Ham Member QRZ Page

    I have a al80a with a blown IG meter. Is there someone who has a drop in replacement. Tried Ameritron but no luck.
     
  2. W1QJ

    W1QJ Ham Member QRZ Page

    What do you mean no luck with Ameritron? The meters in the big three should work just swap the face, worse case you change a resistor boom done.
     
  3. N8VIL

    N8VIL Ham Member QRZ Page

    Check out the Ameritron AL-1500 meter movement. It appears to be the same. May be the same movement with a different face that can be swapped with yours.
     
  4. W1QJ

    W1QJ Ham Member QRZ Page

    Go to the other meter that’s good and remove one wire to isolate the meter from the circuit. Measure the resistance of the meter with a vom and report the reading.
     
  5. NM7G

    NM7G Ham Member QRZ Page

    What do you mean by "blown"? Does it show visible damage, like blackened, or is it simply unresponsive (no deflection)?
     
  6. NM7G

    NM7G Ham Member QRZ Page

    The objective for doing this must be defined first. If you seek an accurate measurement of internal meter resistance, VOM input impedance must be quite high.
    Don't try this with a Radio Shack $14.95 meter. Before I put any current through the meter, I'd first measure just the series resistor. Possibly it's blown, or way off specified value.
     
  7. W1QJ

    W1QJ Ham Member QRZ Page

    The AL80a meter has a 1 ma movement. Most any digital ohm meter can easily measure that meter impedance with barely raising the meter half scale. Typical big Ameritron amps use the same style meter which has an IR of 300 ohms. If his meter reads 300 ohms it’s the same meter and can order one from Ameritron and swap the meter face. If it’s higher it probably has an added resistor inside that can be removed and will probably be 300 ohms. Measure the meter and report the reading.
     
  8. W1QJ

    W1QJ Ham Member QRZ Page

    Sometimes there is a series resistor inside the meter that blows out and the movement is still good. Maybe, maybe not, it’s got to be opened up and looked at.
     
  9. W1QJ

    W1QJ Ham Member QRZ Page

    I checked the 80a schematic and parts list and oddly one meter resistance is 420 ohms and the other is 450 ohms. This tells me there is probably added resistance to the typical Ameritron meter movement. That means you can buy a meter from Ameritron and add the appropriate resistor inside and you’ll be in luck. If you are really lucky then the added resistor is blown and the meter may still be good and you only have to replace the resistor.
     
  10. N8VUL

    N8VUL Ham Member QRZ Page

    The spring is broken on the needle
     

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