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Al-82 high temperature sensor

Discussion in 'Amateur Radio Amplifiers' started by N7UVH, Jan 17, 2021.

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  1. N7UVH

    N7UVH XML Subscriber QRZ Page

    How to the group.
    I’m looking to find where the high temperature sensor the cats out when the amp gets hot on the AL 82.
    I think mine is faulty
    Tubes done get red and shut off the relay to transmit. Amp is not very old.
    I am thinking it is behind the tube wall, next to the choke?
    Black maybe carbon looking part.
  2. N7UVH

    N7UVH XML Subscriber QRZ Page

    I should say the tube do no get red
  3. N7UVH

    N7UVH XML Subscriber QRZ Page

    Also I should add that after it cools down for about two minutes the xmit relay will kick back on.
  4. W1QJ

    W1QJ Ham Member QRZ Page

    There is no such thing on an AL82. Amp does not shut down with any heat issues. Is there a problem you are experiencing?
    N7UVH likes this.
  5. NK7Z

    NK7Z XML Subscriber QRZ Page

    N7UVH likes this.
  6. WG7X

    WG7X Platinum Subscriber Platinum Subscriber QRZ Page

    The only amp that I've ever had with a temperature sensor in it was the Kenwood TL-922. That one has a temp cutout in the transformer. I never managed to get my '922 hot enough to trip the sensor, but one of our local hams has done it more than once. I keep telling him not to drive the amp so hard, but he continues to do so. So, far the sensor / breaker has reset every time, but I really don't know how long that it will keep doing that. One of these days, he's gonna trip it for the last time...

    At any rate, my Al-82 has never had any temperature related problems either. The cooling system on it is correct for the tubes. 3-500 tubes really need the airflow to be directed around the pins first and them up over the tubes. That requires chimneys and a blower, both of which are present on the AL-82.

    So, back to your problem: Listen to Lou @W1QJ. He knows what is what and will most likely be able to direct you to the problem.
  7. N7UVH

    N7UVH XML Subscriber QRZ Page

    Thanks for that info. What happens...
    in rtty or digi modes.. everything seems ok.
    When in SSB and mode switch in ssb if I talk in a qso for more then about 15-20 mins, exhanges maybe a few mins long, amp seems to be getting hot
    and will not xmit.. let it sit for about 3 mins, I can hear a click I think.. and xmit is back. I did call Ameritron, and tech I talked to thought there was a thermo switch. This amp is new.. maybe a few months old.
    What I think is odd.. 100% seems ok.... ssb even less then a KW will shut something off.
    I have the fan speed to Max... moved the power lead. I am going to run it again and see if I can
    confirm of a click.
    tnks for you help. I really dont want to have to pack this up and send it back right now.!!
  8. G3YRO

    G3YRO Ham Member QRZ Page

    My TL-922 used to cut out if I was operating CW in a contest for several hours.

    I just removed all the Voltage Selection stuff on the back, and fitted a new 240V fan behind the two transformers (and replaced the original PA fan too, so both were the same).

    It's a worthwhile mod . . . because if you've been operating for a few hours, as much heat comes out the Transformer Fan as does the PA fan ! (and the Heat Sonsor Cutout has never gone off since)

    Coming back to the OP's question . . . maybe somebody has done a modification?

    If not, I know some Relays can stop working if they get too hot.

    Roger G3YRO
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  9. W1QJ

    W1QJ Ham Member QRZ Page

    If you bought that amp brand new then it definitely does not have any thermal cut out switches. If you bought it used then all bets off. Assuming it’s totally stock and the amp shuts down at some point when it gets warm them there is a poor solder joint someplace or a loose screw in the RF chain. A trained eye will spot the problem in a minute. Can you post some clear pictures of the RF deck?
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Also...if you hear a "click," you can confirm if that's the internal T/R relay by just watching the front panel. If that relay drops out ("click") the XMT lamp will go dark and the plate current meter (Ip) will fall to zero.

    Of all the modes you can use, SSB should generally cause the least amount of heating, unless the amp is really mistuned.

    None of the Ameritron "tube" amplifiers have a thermal cut-out of any kind.

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