Acom or Ameritron...??

Discussion in 'Amateur Radio Amplifiers' started by W3AMM, Jan 3, 2017.

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  1. K3RU

    K3RU Ham Member QRZ Page

    W1QJ: When I get back to troubleshooting my AL1500 I will print out copies of the many emails sent to you containing the results of all the measurements and tests I conducted on the amp. Those emails documented to a nauseating degree the problem(s) with my amp and will be my guide "the next time around" with the amp.

    I'm not sure if you actually read all those emails as your replies seemed a little vague. I'm not complaining as I tend to be very "wordy" and if I received emails as detailed as I sent you I'm not sure I would be patient enough to read them carefully. Your several suggestions proved pivotal in the troubleshooting and allowed me to "zero-in" on what I think is the issue with the amp. I thank you for that.

    Unlike before, I am now "armed" with parts, and have the very heavy amplifier moved to my test bench, where unlike my operating table, I can "get serious" with the amp and rip into it and fix the damn thing.

    I like things that work. After 50 years of amateur radio, and spending most of my working life "fixing things electrical and electronic" I'm now retired and all I want to do is get-on-the-air and operate. I have little or no patience with very expensive gear that doesn't live up to it's cost. That is why AMERITRON "is on my list" as a manufacturer to be avoided.

    And.....it would be nice if AMERITRON included AN ACCURATE AND COMPLETE SCHEMATIC with their products, especially the AL1500. What a disappointing outfit AMERITRON is.
     
    Last edited: Jan 5, 2017
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Just that a kW amp is only 1.77 dB down from a 1500W amp, so the law of diminishing returns (cost vs. improvement) is really exemplified (e.g., an AL-80B at 1 kW PEP is half the cost of any 1500W amplifier and "almost there.").:)

    Then, the same law evidently applies to antennas, too. To pick up 3 dB additional gain, you typically have to double antenna size/weight/windload, so the "first 6 dBd" or so is the best deal -- after that stuff starts getting a lot more expensive!
     
    N5WVR and K8PG like this.
  3. K0OKS

    K0OKS Premium Subscriber QRZ Page

    Sorry to hear the AL1500 does not come with a schematic. Before I bought the AL-80B I made sure there was a schematic available because I like to repair and tinker with things. This was right after checking the price of the tube.

    I certainly understand about not wanting to spend time fixing things, but rather on the air. I am in a place right now where I get almost as much fun out of repairing things as doing anything else radio related. But I have certainly had the frustrating piece of kit or two that I just couldn't fix.
     
  4. K3RU

    K3RU Ham Member QRZ Page

    KE0KZI: The AL1500 does come with a schematic. But - the schematic is not accurate or complete in at least three areas I have found so far. The antenna switching relay circuit on the schematic grossly does not match what is actually in the amp. The zener bias circuit is also incomplete. The 12VDC circuit on the meter board is confusing to say the least.

    I can live with their "black box" approach to the overall schematic in that I realize that everything cannot be put on a one page schematic. At this point I consider the AL1500 schematic as a guide rather than a roadmap.

    What I can't live with is INACCURACY. I suspect AMERITRON is either lazy or secretive. Neither is acceptable.
     
    Last edited: Jan 5, 2017
    K8PG likes this.
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I think it's "lazy."

    The amp's designer has more detailed circuit information than Ameritron publishes, as though Ameritron is always behind -- maybe years behind.

    Of course, I've had Henry amps with many undocumented factory changes so their schematic and parts list didn't agree with what was shipped, either.:p
     
  6. K3RU

    K3RU Ham Member QRZ Page

    WB2WIK: I will fix my AL1500. This amp is well worth repairing and when working it is a great amp and has gotten me through many a pileup. I'm in too deep with it $$$-wise to let it go and really like the RF power it is capable of generating - even though I never run it anywhere near it's limit.

    I have gone off on several tangents in the "new rig" area and temporarily set the AL1500 aside. The new AL80B at the moment is all I really need so the AL1500 is not a "critical must-fix" item now.
     
  7. W1QJ

    W1QJ Ham Member QRZ Page

    In your case the chassis is obviously hot with a few volts or fractional volts of AC. It's got to be leakage. It's either a bypass cap to ground off some AC somewhere or leakage through a transformer case. Time spent looking in the possible offensive areas should eventually turn up the problem. It's true that Ameritron hasn't updated many of their schematics. The newer amps with the new dual relays are not shown in the schematic nor the changes to the meter board in regard to the relay board change. One could get totally screwed up looking at a newer meter board and checking it against an old schematic. The new board has an additional 12 volt doubler circuit on it to go along with the dual relay board.
     
  8. K3RU

    K3RU Ham Member QRZ Page

    W1QJ: I thought the "12vdc" circuit was a voltage doubler from what I could see from looking at the installed meter board. I am suspicious of the filament xmfr because of the extra winding besides the tube filament secondary. When I get into the amp I will have it pretty much torn apart on the power supply side because the "new" (and damaged - thanks Ameritron) filter cap board will go in - and possibly a new filament xmfr which I have on hand. A new $800 CHINESE 8877 is also on hand should the original EIMAC 8877 tube prove defective. It took me a while to talk myself into buying another 8877 but if I don't need it, I will use the CHINESE 8877 as it is under warranty and I will save the original EIMAC 8877 as a spare as the warranty on it ended about 7 years ago. I also want to take a look at the component side of the meter board and if necessary draw my own schematic.

    Speaking of the new antenna relay board, I purchased one just to see what it was, as installed in the amp you cannot see all that is on the "back side" of that board. For a cost of I think it was $40 it is quite a complete little relay assembly and has many possibilities other than in the AL1500. I am impressed with it and doubt I'll have to install it in the AL1500 and could very well make a very nice little "coax relay" out of it. Those little sealed relays actually handle the output of an AL1500? Up to 2500watts? I'm liking that little part a lot!

    It won't be long until I start on the amp. All this talking about it has got me anxious to fix it.
     
  9. W1QJ

    W1QJ Ham Member QRZ Page

    The filament transformer the the Al-1500 and 1200 and 82 are quite "busy". They have several input taps and taps for the various fan speeds as well as the 12 AC supply for the relays and then of course the filament winding. I haven't see a schematic yet for the new meter board with the doubler circuit. There is a hand drawn circuit floating around the net for that new relay board. I believe it was the schmeatic and pictorial Tom drew for the Ameritron guys. It is a bit crude though. I guess you haven't tried the new Chinese tube yet to see it the hum is still there. I hope you track it down.
     
  10. W1VT

    W1VT Ham Member QRZ Page

    A legal limit is nice if you can afford it, but you may need to factor in more than just the cost of the amplifier. You need 240V service to run a legal limit amp--so you may need to hire an electrician.

    In my case, I figured out that I could meet my operating needs with a 600W amp--working DX on 160M with 600W is actually easier than trying to work HF DX with 1 watt and a wire--and I did a lot of that in the 1980s.

    Zack W1VT
     

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