Possible new Direct FET replacement found

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    • September 24, 2004 at 4:16 pm #12351
      Avatar photoAaron
      Keymaster
      • Posts: 2146

      Hi Everyone,
      Was ordering another batch of IRF7389s and made a typo in the partnumber, it gave me a match with a different HEXFET from IRF that seems to be a good replacement for the IRF7389.

      At the 4.5v of a Mini-Z circuit it has a internal resistance about 30% lower than a IRF7389.

      Drawbacks are a slightly lower current rating (6A vs 7.3A)

      The other GREAT news is they re also cheaper than IRF7389s which have had their wholesale price creeping up higher and higher for the last year.

      I m getting 20 of them to test out… Details shall be posted.

      A.

      --
      Site Owner Guy.

    • September 24, 2004 at 8:31 pm #55690
      mocky
      Participant
      • Posts: 239

      wicked. interested to see how they go.
      ph2t ur opinion?

    • September 25, 2004 at 8:36 pm #55708
      Avatar photoAaron
      Keymaster
      • Posts: 2146

      They’re still not going to beat a Nelly… But for people like me with “X-Speed” level motors they’re more than fine for the ‘stealth’ look..

      A.

      --
      Site Owner Guy.

    • September 26, 2004 at 5:51 am #55721
      jamiekulhanek
      Participant
      • Posts: 2563

      i dunno, id say a nelly 1.1 is equivalent to a 6×2 stack….in my experience…

      Aaron if they are any good i’d like to place an order for 12 or so of them.

    • September 26, 2004 at 1:37 pm #55724
      ph2t
      Participant
      • Posts: 2088

      jamie, check out my recent posts in my nelly turbo thread, an interesting read! theory shows that nelly is better than that, but it’s reality I guess that makes or breaks the bottom line….

      as for the new fets, a better price and lower Rds(on) is always good, good luck Aaron!

      ph2t.

    • October 3, 2004 at 7:18 pm #55897
      jamiekulhanek
      Participant
      • Posts: 2563

      Yeah well as i said it’s based on my real world testing, my 1.1 gets quite hot, almost hot enough to melt the heatshrink.

    • October 3, 2004 at 9:38 pm #55899
      SausaGe_LinK
      Participant
      • Posts: 96
      Quote:
      Yeah well as i said it’s based on my real world testing, my 1.1 gets quite hot, almost hot enough to melt the heatshrink.

      Yup, mine gets hot like that too, as long as she doesnt die tho then im happy 😀

    • October 3, 2004 at 9:47 pm #55900
      ph2t
      Participant
      • Posts: 2088

      hmmm, on the xmod then it’s gotta be the low drive voltage of 3.4V…. i read on trc that it’s like this, gotta do my own testing yet on the xmod, it’s takeing fuckenforever to strip/clean/rebuild……

      ph2t.

    • October 4, 2004 at 1:24 am #55902
      jamiekulhanek
      Participant
      • Posts: 2563

      matt whatabout a FWD only design for a nelly, how much better would that be?

    • October 27, 2004 at 6:54 pm #56487
      Avatar photoAaron
      Keymaster
      • Posts: 2146

      I have tested the IRF7317s in 2×2 stacks in genuine Japanese MR01, Chinese MR01 and now in a iWaver 01.

      Each test has been a total success and it appears these FETs are well and truely delivering the promised greater performance than the venerable IRF7389

      A.

      --
      Site Owner Guy.

    • October 27, 2004 at 7:34 pm #56493
      snailpace
      Participant
      • Posts: 58

      Hey Aaron, got the steering servo and 7389 (x10) FETs today, thanks for the fast delivery! Just looking at the board (Kyosho) orientation with the FETs right next to the drive motor terminal mounts (next to black box), do i just stack 5 on each after removing the 2 stock ones? Do i need to do anything about the stock FETs on the left side where the wires lead to the steering servo and sensor?

    • October 27, 2004 at 8:14 pm #56497
      Avatar photoAaron
      Keymaster
      • Posts: 2146

      You got it!

      Just remove the two original FETs near the motor terminals, and solder two stacks of 5 in their place. It goes pretty easy 😉 I generally build the stacks on the board, and ‘pair’ the output legs in solder for physical support.

      Orientation in the same.

      The other two are the steering FETs and can be swapped as a pair if one blows.

      Hope the new servo doesn’t twitch like the old one!

      A.

      --
      Site Owner Guy.

    • October 28, 2004 at 2:03 am #56502
      snailpace
      Participant
      • Posts: 58

      Thanks Aaron, will give it a try and let you know how it turns out. Hope the servo works too! If it doesn’t i’ll bugger it off and get me a real MR02!

    • October 28, 2004 at 4:22 pm #56526
      snailpace
      Participant
      • Posts: 58

      Finally got the FET’s installed in the monster and she’s running again. TOTALLY NUTS! Stock motor: 10kph, X-Speed motor: 18kph, X-Speed Pro motor: 22kph. I love it! Yet to test the steering servo. Thanks Aaron!

    • October 28, 2004 at 8:44 pm #56531
      snailpace
      Participant
      • Posts: 58

      Noticed after a while the reverse does have that initial kick like forward. Any ideas? Is one stack of FETs for forward and the other for reverse? Which one is which?

    • October 29, 2004 at 2:41 pm #56540
      ph2t
      Participant
      • Posts: 2088

      check your throttle trim out, it might be biased to fwd….

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