706mk2g weird swr power problem

Discussion in 'General Technical Questions and Answers' started by KG7HVR, Oct 28, 2018.

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  1. KG7HVR

    KG7HVR Ham Member QRZ Page

    Yeah i did my ts450sat and a old 440 someone buggered. Ill go back thru and start from scratch
     
  2. K3RLD

    K3RLD Ham Member QRZ Page

    As an aside, it appears that I have an early MK11G, so while there is nothing I can do to plan for the future, at least I should be able to tell if/when I blow my finals. I don't have an RF power meter, but my power supply has an ammeter on it. When the finals blow, does the current draw during Tx drop? As it is right now, I see somewhat appropriate levels of current during Tx (and the most important factor is that people can hear me on the other side of the pond, etc).
     
  3. KG7HVR

    KG7HVR Ham Member QRZ Page

    If they go, no current will be drawn. I personally think you can get these finals and grind down the edges of the metal tabs to fit in your PA board.
    That is why the new finals don't fit in the old board without cutting the board the heatsink tabs are too big but when you look at the old ones the center of the transistor is round as opposed to square and actually looks bigger
     
  4. KG7HVR

    KG7HVR Ham Member QRZ Page

    I don't like how warm these radios get opposed to the original 706 but I don't know that I trust the fan modification that's posted on the internet they are soldering to an RF choke that just kind of strikes me as odd
     
  5. KI4WCQ

    KI4WCQ Ham Member QRZ Page

    I like this AD5X modification for adding a fan. http://www.ad5x.com/images/Articles/Fan706RevA.pdf
     
  6. AI3V

    AI3V Ham Member QRZ Page

    Now that would depend if the final failed open (usually from a over current event) or failed shorted (voltage spike event)

    Of the several thousand transmitters I've repaired I'd say you have a 50/50 chance of each.

    Rege
     
  7. KG7HVR

    KG7HVR Ham Member QRZ Page

    Yeah that's a lot better of an idea than the one where they tap that RF ferrite choke and like I don't even know what that thing feeds but it's an RF choke and it seems like if it's in part of the transmitting chain and you're hooking a 200 Ohm resistor to it it seems like it would do something strange I've got a little fan floating around here somewhere I've been trying to look for since yesterday and I was going to do that exact same thing the only problem is I do use an automatic tuner so I would need a piggyback for the antenna plug
     
  8. KI4WCQ

    KI4WCQ Ham Member QRZ Page

    His mod incorporates the automatic tuner. I think it's in the last para and shows a pigtail.
     
  9. KG7HVR

    KG7HVR Ham Member QRZ Page

    I found my little fan now the question is do I needed to blow in or blow out....hmmmn 20181208_214214.jpg 20181208_214221.jpg
     
  10. KG7HVR

    KG7HVR Ham Member QRZ Page

    His mod says to have the fan blow away from the heat sink however I don't know which direction the internal fan blows I used the fan and some red butt connectors which fit in very snuggly between the fins. 20181208_221822.jpg 20181208_221818.jpg
     
    WZ7U likes this.

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