40m not working on AL-80B amplifier

Discussion in 'General Technical Questions and Answers' started by KB7QPS, Oct 10, 2018.

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  1. KB7QPS

    KB7QPS Ham Member QRZ Page

    On my Ameritron AL-80B amplifier, it works on all bands except 40m. It appears to simply pass the signal through without amplification. I can make (unamplified) contacts just fine, the needles work just fine, but no amplification is done.

    It acts the exact same way as when I use it on 20m but have the band selector switch set for 80m. No amplification, just signal pass through.

    I have opened it up and done a visual examination of the components inside. Everything looks fine. No opens, no shorts, etc.

    Not really sure what to check out. Any good places to start? I will not be powering it on with the case off due to HV hazards, so any testing will have to be unit off. I could also take it someplace in Seattle to have it repaired, but don't know who might work on them.
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    When you say "needles work just fine," does that mean that on 40 meters when you try to use the amplifier, the Ip and Ig register normally as if it's amplifying (maybe 400 mA Ip, 150 mA Ig or so)? If so, when you try to "tune up" using a carrier, do the PLATE and LOAD controls impact anything at all, or nothing?
    WB5YUZ likes this.
  3. W1FBV

    W1FBV Ham Member QRZ Page

    This can be the situation if you have not tuned the plate and load controls correctly. Make sure you have a 50 ohm load and retune the amp.

    Jim, W1FBV
  4. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Has it worked for you before and then something changed, or has it always been like this (how long have you had it)?
  5. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Without clear answers to Q #2, impossible to diagnose.

    With good answers to those easy questions, I can tell where the problem is. (I have an AL-80B and know it really well.)
  6. KP4SX

    KP4SX XML Subscriber QRZ Page

    Don't do that.
    KA2FIR and WB5YUZ like this.
  7. WG8Z

    WG8Z Ham Member QRZ Page

  8. KB7QPS

    KB7QPS Ham Member QRZ Page

    The needles work the same as if it is in standby. Ip and Ig are at zero. Power output needle shows less than 100w.
  9. KB7QPS

    KB7QPS Ham Member QRZ Page

    No, amp acts like it is in standby regardless of plate and load controls.
  10. G3YRO

    G3YRO Ham Member QRZ Page

    So when you switch to Transmit on your Transceiver - but without any drive (ie not talking into the mic or sending cw) - you should hear the Relays go over inside the Amplifier. Do you?

    At the same time, you should see the PA Current increase to the Standing Current (I'm guessing around 100mA). Does this happen OK on 40m ? (like I presume it does on the other bands)

    And if that's the case, what happens when you then give the Amp some Drive - does the PA Current increase?

    Also . . . you didn't answer questions others asked - has this fault suddenly started happening? Or have you just bought this Amp?

    Roger G3YRO

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