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Yaesu FT-847, MFJ-998 and ALS-600

Discussion in 'Amateur Radio Amplifiers' started by N5TEN, Jun 29, 2012.

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  1. N5TEN

    N5TEN Ham Member QRZ Page

    Response from Ameritron after several back and forth messages on the equipment, situation, etc.:

    "If it is that old, it does not have the +12VDC regulator issue. You might want to check and see what other appliances and devices you have plugged into that same breaker circuit. If you have something like a window mount air conditioner, it could draw enough current to cause your power supply to detect a brownout condition and it would shut down. Also, depending on where you have the power supply and how well ventilated it is, the power supply could be overheating and causing a shut down. Lastly, you could have a final that is about to go out, and every once in a while, the power supply sees too high of a current drain which would also cause it to shut down."

    It is my conclusion, because of my station's particulars, that the Power Supply is over heating. I'm going to take steps and see what happens.
  2. N5TEN

    N5TEN Ham Member QRZ Page


    Testing the amp with Ameritron helping: The amp issue happens ONLY when using SSB. The amp operates fine on CW, AM, and FM no matter how hard I drive it, or how low I drive it. I can tap CW with the amp on for 20 minutes and no shut off issue.

    In SSB, the amp shuts off constantly after about 10 minutes of operation time. The only time it doesn't fault, is when I turn the drive power so low, that the amp output is 100-150 watts SSB. The mic gain is also down and the mic is non-amplified. (we went all through that).

    Ameritron says the amp either has a power supply problem or a final is ready to go out. They are asking I ship it to them. Maybe I can get it updated with some things too.
  3. KO6WB

    KO6WB Premium Subscriber QRZ Page

    There are some other things that could be at play. The keying of a lot of the modern transceivers has a intial spike of power. This spike can be considerable and it usually requires an oscilloscope to see it. You would also have to know what you're looking for and when it is supposed to be happening. This can occur at any power setting including a setting of zero watts. It is more predominant on SSB due to it's control and switching in the ALC circuits. There are times when just about every leading edge of a transmission, even spaces between words, have the leading edge power spike.
    The way to help control that is by using the ALC from the ALS-600 to control the peak power output of the FT-847. This appears to be very effective and the ALC control circuits from the ALS-600 are very good.
    The folks here on QRZ try hard to assist others with problems. Not knowing the actual skill levels of the poster means that sometimes the explainations appear to be talking down to those that ask a question. Keep in mind that the person asking the question is not the only one that will be reading it. A lot of folks check in on various postings because they are curious and want to learn something as well. So an answer will be basic at the start and go up from there. Another thing that helps is to respond to what was suggested by posting a reply to the folks trying to assist. Either their suggestions worked or the problem is still there. At which time the suggestions will focus on other directions.
    It's hard to troubleshoot anything on the internet. Often takes several days if not weeks to go through the process. While, in the good ole days, you had an Elmer looking over your shoulder and usually the problem is resolved in a few hours or less. So hang in there and by all means if you have an experienced amateur local then seek them out. They will help you if they can. (Exception: there are some grumpy characters that are hard to approach.)
    Hope this helps
    Last edited: Jul 8, 2012
  4. N5TEN

    N5TEN Ham Member QRZ Page

    Thanks Gary,

    Here's an update:
    Looks like the 847 was the cause of the issue, or at least partially the cause. I found out that the radio's SSB was having serious tx distruption, but that wasn't originally apparent using that old stock mic. When I received my Heil mic cable and hooked it up, it was immediately apparent that the sideband tx was really messed up in the radio. The mic worked beautifully on FM, but not at all on SSB. So, whatever that issue is (probably RF in the ssb tx), it was shunting my amplifier.

    So, I contacted the seller of the FT-847 who is a guy named Ron KK7RON and asked if he knew the radio had a sideband problem when he sold it to me for $900. No response. (see my buyer's review of this transaction).

    I sent the radio to Yaesu Service. As of right now, the radio and my amplifier are both out for service.

    Hopefully, all the issues, including if there are other contributing factors with the amp, are solved on return of the equipment. Either way, I'm out a bunch of money because of a weasel who sold me a faulty piece of equipment. I will probably take him to court after I get all the costs of repair together. One last certified letter to him and then I'll send the sheriff over there with a summons.

    73 de N5TEN
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