Ameritron AL-80b questions

Discussion in 'Amateur Radio Amplifiers' started by NB4R, Nov 4, 2018.

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  1. NB4R

    NB4R Ham Member QRZ Page

    I have a Yaesu FT1000-MP connected to an AL-80b connected to an MFJ-989c into a 160 meter loop. I can tune 160, 80, 40, 30, 20, 17, 15 and 10 meters all to almost to a 1:1 swr with the amplifier in standby. With AL-80B in operate I can tune and load the amp good in 160, 80, 40, 30 and 20 meter positions. With the amp in the 17/15 meter position and exciter in transmit I get some grid current and plate current. There is no output and the radio swr meter indicates 3:1 (high swr). I am hoping this is an indication of mistuned input circuit. I've not had a chance to try to tune this. Also with the amp in the AUX position I can tune the load the amp with the radio on 15 meters. I discovered this by accident. In the AUX position I cannot tune 12 or 10 meters.
    I looked and the 10 meter jumper has been clipped. The 15/17 meter jumpers are intact.
    I purchased this amp a couple years ago used. I t is physically in excellent condition. I realize that there is no telling what someone may have done to it. I have never switched the band switch while transmitting and the band switch looks good. My questions are:
    1: Could the 15/17 meter coil be so mistuned that both ranges look very bad?
    2: What should I be seeing, tuning wise, with the 15/17 meter jumpers intact?
    3: Should I be able to tune either 15 or 17 meters, but not both unless I cut the jumpers?
    4: Is it possible the 10 meter coil can be so mistuned that it I can actually tune the amp to 15 meter frequencies in the AUX position ?

    I've read numerous threads that pertain to this subject. I'm just seeking more information. It just seems so strange that four positions are working properly and two are that bad. I also want to know what else I could be looking for when I tear into it. I did't notice if the radio's swr meter was reading high when I was trying to tune 12 and 10 meters in the AUX position. I'll check that when I can get back to the shack. Any information and opinions are welcomed and appreciated.
     
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    What 15/17 meter jumpers? There aren't any.
    Sure, especially if someone screwed around with the tuning. Or, if someone drove the amp with a higher powered exciter (>100W output) so they destroyed the capacitors in the input tuning network.
    What jumpers? The AL-80B is factory set-up for 15/17m, there aren't any "jumpers." The only "jumper" is the one that shorts the input to ground in AUX, and that's the famous "green wire."
    There aren't any jumpers for 15/17m, it's factory set up for those bands.
    Could be, if someone screwed around with the amplifier. From the factory, that would be about impossible.
     
  3. NB4R

    NB4R Ham Member QRZ Page

    I'm just using termin

    I'm just using terminology used by Ameritron in this jpg file I've uploaded. I think the "shorts" you are referring to are Ameritron's "jumpers".
    I'm glad they weren't Ameritron's shorts. That could embarrassing.:eek:

    You verified what I was thinking. I didn't think it would come from Ameritron out of tune or whatever condition may exist. This is a learning experience for me. I'll follow up after I have investigated further.

    I Ameritron 15- 17- 10-12 meter Amp Mods-1.jpg Ameritron 15- 17- 10-12 meter Amp Mods-2.jpg
     
    Last edited: Nov 4, 2018
  4. K7MH

    K7MH Ham Member QRZ Page

    If you are going to adjust the tuned input slugs do yourself a big favor and make sure you are using the correct tool to do it.
    A broken slug core is not a happy thing!
     
  5. NB4R

    NB4R Ham Member QRZ Page

    Thank you, I will use the correct tool. My problem is finding a time when I'm not rushed.
    I am looking forward to retirement so much!
     
  6. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Use the proper plastic (usually nylon) hex tool and this adjustment takes all of ten seconds.

    You don't need any kind of "test equipment" to make this adjustment: Peak the slug for maximum Ig (grid current), and if you can't to that in ten seconds, something's wrong with it.
     
  7. K1XS

    K1XS XML Subscriber QRZ Page

    Be careful, I’m busier now in retirement than when I was working 50 to 60 hours a week. A few months into retirement and you will wonder how you got anything done while you were working.
     
  8. W1QJ

    W1QJ Ham Member QRZ Page

    Yes there are jumpers (so to speak) on the 15/17 meter input circuit. You have an option to cut two jumpers on the edge of the input PC board, you can either leave the jumpers intact or snip them. Not sure what leaving them does an what snipping them does, but if I recall, if you leave them intact the input circuit favors 15 meters and if you cut them the input will give you a compromise and both bands.
     
  9. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    My AL-80B (c. 2000) doesn't have that.

    Do you know when they added this?

    I tuned for a compromise between 15m and 17m the day I brought the amp home, and input SWR on each band is around 2:1, which is fine with me. I did try optimizing for just 17m a long time ago and it was a much better match on 17, but 15m mismatch became worse so I left it tuned midway. Works fine and the "adjustment" takes a few seconds.:)
     
  10. W1QJ

    W1QJ Ham Member QRZ Page

    That's right, the older units did not have the option of cutting the traces on the edge of the board. I don't know when this option became available. Since Ameritron does not always update their on line manuals for their amps when they make changes it is hard to tell when this option may have come about. I am not even sure if the manual sent with the newer AL-80B amps even discuss the option of cutting these traces. I don't really know. Most of the time when I look at the on line manuals it is just to look at the schematics and NOT read the techniblather. I could be wrong and the on line manual DOES discuss this issue. I think I will go browse thru the online manual and see.
     

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