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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

    I have been using a Yaesu FT-897, ALS-600 with an MFJ 998 for years. I do this by using a DIN splitter from the 897's Linear/Tuner jack. One cable is the radio to tuner interface (din to phone type to the tuner so when I press tune, it tunes through). The other DIN also goes to the tuner as an amplifier interface.

    Today, I bought a Yaesu FT-847. I put the Y adapter on the Tuner DIN and it worked the same. I can tune the 998 with the radio's tune button, and the amplifier works. But....

    My amp is turning off on me like a temp just clicks, the lights go off and the amp goes dead. I can reset it almost immediately by turning it off and on. It will work again just fine for a while and then do it again. I'm thinking this is an interface cable issue? I'm not sure.

    The interesting part of this is that I can run non-stop CW at 450 watts and no amp problem on the same frequency...just switch from ssb to cw.

    And another weird thing on ssb, is my amp meter says I'm putting out 500 watts, but my 998 tuner says I'm putting out like 19 watts. I tested this on the air and the ham who helped me said my signal went way down when my amp failed out. I turned the amp off and looked at the meters power reading while transmitting with no power, and my radio indicated 50 watts, the amp meter indicated 50 watts, but again, the 998 indicated like 7 watts.

    Perhaps the tuner is reading a good swr but having issues with the match, even though it's showing a 1.4 swr?

    Anyone have any clue as to what's happening? Should I interface this situation differently? I think MFJ sells the cable to go from the CAT to the tuner interface, but they also say the cable won't work for the 847, yet at the same time, will work for any Yaesu that works with the ATAS 100, which this rig does interface with.

    Any help with this would be much appreciated.
  2. W1QJ

    W1QJ Ham Member QRZ Page

    do you have this equipment in line in the order you titled this thread? If so, that is your problem. Lou
  3. N5TEN

    N5TEN Ham Member QRZ Page

    I was going to say something sarcastic, but I've only had a half a sip of my coffee this morning. If you don't know the answers to my question, please refrain from posting. I'm hoping for some help here.
  4. N5TEN

    N5TEN Ham Member QRZ Page

    I will call MFJ and/or Yaesu this morning to try and get some answers about the interface cables.

    Admin, can you remove this thread? Thanks.
  5. NA0AA

    NA0AA Ham Member QRZ Page

    All the patience of a boiling tea kettle.

    Well, if the amp is going into fault mode, it's not liking someting. Was a 1.4:1 SWR acceptable to the amp before? IIRC the SS amps tend to dislike anything above 1.5:1....

    Is is possible you have a bad connection in the RF chain?

    I also asssume you checked all the pin-outs on your cables - I don't know that the 847/897 are fully pin compatible.

    Bad feedline?
  6. N5TEN

    N5TEN Ham Member QRZ Page

    Richard, try to keep it positive, buddy. Stay on topic, rather than how hams think or what they possibly do or whatever. You can help me with the Y connector interface question, and I can help you see how assumptions and stereotyping don't provide solutions.

    Here's the update:
    I called tech support and they say (I'll believe it when I see it), they will be calling me back today. My amp is temp faulting. That's my guess. I can run CW on it for an hour with no problem. I can talk on it for 30 mins off and on without an issue, then it starts temp faulting which means there is no load fault light. The amp just quits and has to be reset via power cycle. If you're familiar with the als-600, this is the heat protection fault.

    So, on the cables and setup... everything worked just hunky dory with the 897 yesterday. Occasionally, I had the temp fault on 20 meters, but not like this with the 847. I did notice that with the 897 the amplifier would max out at 300 watts output. With the 847 I'm peaking at 500 watts, 65 watt drive. I will try turning my drive down to see what happens. Maybe I can only run 300 on this particular band and on 20 meters, as it was doing this last night on that band as well. Maybe the 847 needs an ALC cable between it and the amp as well. I can make one.

    Waiting on the tech guy to call me before I go out of town today. And working on 4 hours of sleep. I apologize if I came off quick on the key here.
  7. N5TEN

    N5TEN Ham Member QRZ Page

    I'm right at 1.5 SWR on the 998 digital readout. (fluctuation btw 1.4 and 1.5 ssb, steady 1.4 swr cw)
  8. NA0AA

    NA0AA Ham Member QRZ Page

    Then, I suspect that on voice peaks, the protection circuit on the amp senses excess reflected energy and does its job.

    To check this, turn down the drive power and see if it works. On SSB of course.
  9. K7JEM

    K7JEM Ham Member QRZ Page

    An amp putting out 500 watts is going to get hotter than one putting out 300 watts. That is probably why you are seeing the temp faults. Try reducing drive until you get to the same output as you had with the 897.

  10. K0BG

    K0BG Ham Member QRZ Page

    This is not an interface cable problem, unless you're using the ALC feedback, and it is not adjusted properly.

    Rich very well may be correct, but I still wonder if this is a common mode problem. From your footer, you're using an A-D dipole, and I assume it is fed with coax. If my memory serves correctly, there is no balun used with the A-D. That, and perhaps it is a bit too close to the operating position, could cause the problem you're having. As suggested, transmit into a dummy load without the 998 in line, and see if the problems persists. That will certainly eliminate common mode, if the coax cables are all okay. Then add the 998 into a dummy load, and check it too.

    As for the 998s SWR meter..... I've never seen anything out of MFJ in the way of an SWR and/or wattmeter that was closer than about ±20%. The 868 I got out of a SK estate wasn't even that close!
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