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HG WTF!

Discussion in 'Amplifiers' started by nomadradio, Jan 18, 2020.

  1. nomadradio

    nomadradio Analog Retentive

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    So here's a wrinkle I hadn't seen before. Detachable collector tabs.

    Maybe these transistors are legit Hua Gao 2SC2879.

    Or maybe they're counterfeit. Put six of these in a customer's amplifier. He supplied them, so I'm not on the hook for defective parts.

    Blew out five of the six transistors. Too much drive, pretty sure.



    But when they were removed, the collector tabs fell off four of them.

    [​IMG]

    Really doesn't look as if the collector tab was anchored inside the transistor case terribly well.

    [​IMG]

    Just when you think you've seen everything.

    [​IMG]

    But clearly it pays to "Vewy vewy caweful" with this part.

    73
     

  2. snow bird

    snow bird Well-Known Member

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    What Dose it look like on the inside Please??
     
  3. dave457

    dave457 Sr. Member

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    Did you ask where the customer got them from?
     
  4. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Are they 2016 Year date - am I reading that right?
     
  5. nomadradio

    nomadradio Analog Retentive

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    That's probably what the date code means.

    The customer got them from "a friend".

    Didn't know where the friend got them.

    73
     
  6. Ranch55

    Ranch55 Well-Known Member

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    Yes, that is the very issue I have seen on using the HG transistors. I have had that happen on the 2879's and the 1446's ......
    That is the issue that I commented on in another thread about the HG's being inferior quality.
    They usually do perform pretty well, just not very robust compared to the "old" Toshiba's or the ST Micro's .......
    That is why I have said before that they are very delicate ........
     
  7. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    They are only capable of 80% of what the Toshiba's could do. Keep that in mind while you setup the quiescent current and drive levels.
     
    Tokin likes this.
  8. Shockwave

    Shockwave Sr. Member

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    When I saw the guts of this transistor, it actually had four small transistors on the die to mimic the performance of the 2879's one large wafer. This requires extra space between each of the four used in the aftermarket device to insulate them. That leaves little surface area left to bond the metal tabs to the ceramic case.

    Now for the bad news. Notice this is only happening on one tab. The one with the most DC and RF current on it. It's also the one with the most RF heating with thermal expansion and contraction occurring. This "thermal creep" is the likely cause of the collector terminal snapping off the case.

    The datasheets for some high power parts suggest that the leads be bent in an upside down "U" shape, as they exit the case to allow for this thermal creep. Bending the tab over a piece of small solid wire is an easy way to do this. Just be careful not to use enough pressure to break the case and don't let solder get across your bend on installation. Bend the tab up before you try and bend it around the wire, to reduce pressure against the case.
     
    #8 Shockwave, Jan 19, 2020
    Last edited: Jan 19, 2020
    Woody-202 and Shadetree Mechanic like this.
  9. Tokin

    Tokin 42Zero Tampa

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    Lol, more Chinese junk? As ive stated im not even close to being impressed with any of the toshiba replacements and this doesnt surprise me a bit.
    Sorry to see all your hard work go up in smoke. Thats what sucks the most.
     
  10. Shockwave

    Shockwave Sr. Member

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    I've been saying it for years, if these transistors were any good, they would be in the back of every 12 volt HF rig. They are in none for a reason and it's not price, it's reliability. That type of reliability will not return until we start copying what they are doing again.
     
    Tokin likes this.
  11. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    What do most of the new HF rigs use? Anything we can reasonably adapt to our current platform?
     
    2NC995 likes this.
  12. Shockwave

    Shockwave Sr. Member

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    Most are using Mitsubishi transistors. Older ones were using what was left of the bipolar transistors while newer ones have 12 volt RF MOSFETS. The new case is a little different shape and its input impedance is different enough to require some work to our existing circuits. Here is one part in common use today: RD100HHF1C

    The datasheet for this part can be viewed here: http://www.mitsubishielectric.com/s...ghfrequency/siliconrf/discrete/rd100hhf1c.pdf
     
    #12 Shockwave, Jan 19, 2020
    Last edited: Jan 19, 2020
  13. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    Don't forget you can parallel them with very few problems.
     
    Shadetree Mechanic likes this.
  14. Tokin

    Tokin 42Zero Tampa

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    Reliability and quality supply issues are the reasons I wont mess with todays pills/pill amps. Replacement, not even matched Toshiba's are $200+/pill so buying older units are a crap shoot too. The days of reliability at a decent price are over, for now. Im believing mosfet tech will continue to get better and will replace pills altogether and maybe become the new cheap/reliable. Only time will tell. Until then im going back to the old reliable $40 sweep tube lol.
     
    WECSOG and Shadetree Mechanic like this.
  15. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    That should make a 32 pill with them easy.....:whistle:
     
    Tallman likes this.

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