Auteur Sujet: Sega G-loc down again :(  (Lu 423 fois)

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Sega G-loc down again :(
« le: Jeudi 30 Novembre 2017, 10:47:31 am »
  • Hi There :)

    Goodday to all in the forum, I am writing again because my Sega G-loc deluxe is down again  :'(



    I have restored the powersupply in this tread http://www.gamoover.net/Forums/index.php?topic=36585.0

    And it had worked great,  I have played the game, and it had been fun :)
    But yesterday when I where playing.. suddenly BANG... and power where out and a bad smell....

    So now my beloved Sega gloc is down one more time.

    I have looked at the powersupply and it is the same one that i rebuild who has failed, the one who is powering the right motor



    It seems visual that it is the K1250 mosfet who has been fried




    A bit at the corner


    What can cause the K1250 to be fried?

    Hopefully GC339 and all the other great people who helped me the last time is still around, and see my post :) you where all super help last time

    My plan so far..get the energy back :) - take a deep breath, coffie-- think, more coffee and then :)
    Remove All the Mosfets at the H bridge and test them all, and replace the bad ones.
    But what might had caused the breakdown..?

    Kind Regards
    Per
    « Modifié: Jeudi 30 Novembre 2017, 11:00:58 am par perjmolsen »

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    Sega G-loc down again :(
    « Réponse #1 le: Jeudi 07 Décembre 2017, 19:17:34 pm »
  • Hi

    A small update

    I have followed the steps in this repair guide
    http://www.gamoover.net/Forums/index.php?topic=28660.0

    Step 1 to 3 is complete and all checks out OK, so far so good  :-)=

    But step 4 there is no input voltage at "D9" - so i have to figure out why.  =?=
    so i am stuck at this step at the moment

    If any have some imput please feel free to comment :)

    Kind regards
    Per

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    Sega G-loc down again :(
    « Réponse #2 le: Jeudi 15 Février 2018, 11:33:40 am »
  • HI

    Just an update - I hope that CG339 might still be around to help me out this time also :)


    I now have managed to get a bit longer in step 4 in this guide. > https://www.gamoover.net/Forums/index.php?topic=28660.0

    I now have:
    Input at D9 = 18,3 V
    ZD3 = 15,4 V (changed Q5) then it where OK

    But output at Vpc7 and Vpc8 is to high, I measure it to 15,4 V it must be 5 V
    I have changed IC9 and IC10 but still high voltage.

    Hope that someone can help me a bit :)

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    Sega G-loc down again :(
    « Réponse #3 le: Dimanche 18 Février 2018, 22:26:10 pm »
  • Hi,
    i have finally find the time to look again at this drive board.

    First thing:
    Citer
    But what might had caused the breakdown..?

    cg339 told me this:
    "Concernant les transistors 2SK1250, ce sont des transistors MOS, plus exactement VMOS. Et comme tous les transistors VMOS de puissance, ils ont une capacité gate/source très importante, de l'ordre de 5 nF, ce qui est énorme. Il convient donc de charger très rapidement ce condensateur parasite pour assurer un passage de l'état OFF à l'état ON immédiat du VMOS et de le décharger encore plus rapidement pour passer instantanément de l'état ON à l'état OFF. Le danger serait que les deux VMOS d'une même branche du H soit à l'état ON simultanément, même fugacement, c'est leur destruction assurée. C'est ce qui justifie la présence de la circuiterie d'assistance entre les photocoupleurs et les gates des 2SK1250 (http://www.gamoover.net/Forums/index.php?topic=28660.msg458883#msg458883) et c'est pourquoi il est indispensable de tester cette circuiterie et de vérifier les signaux à l'oscilloscope comme je l'ai fait sur chaque source de 2SK1250 (simulation de la capacité gate/source des 2SK1250 dessoudés par des condensateurs réels)."

    i am unable to translate exactly this but it means one thing: one thing goes bad, and the K1250 explodes.

    what appened to you is the exact same thing that appened to me: a bad regulator 78L05 at first an a lot of damage ahead...

    have you check all the tracks on the pcb? on my board some where burned...



    Vpc7 and Vpc8 are way too high, are you sure about your "new" IC9 and IC10? try to replace them with new ones from another seller. its too disturbing... 
    i'm not an expert but can PC7 and PC8 resist a such high voltage? when your 5v is fixed, replace them by security (they cost prety nothing).

    If you have the time, and if you are not an expert like me, change everything:


    (just check R9 and R10 and replace them in,  don't replace them with new one).
    This drive board is way too sensitive and any single part can doo a lot of damage, so personnally i will not take risk with old parts :/
    « Modifié: Dimanche 18 Février 2018, 22:28:56 pm par Vieille_Loutre »