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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/VKXTSEXANEKJQZL6WA7BD2ZKZIJZWFCR/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "001e01c90080$af87db60$0b09a8c0@zeus",
    "message_id_hash": "VKXTSEXANEKJQZL6WA7BD2ZKZIJZWFCR",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/43EM2QRGM3SM3A556ICLGOFOHC36JFVV/?format=api",
    "sender": {
        "address": "sv1bsx (a) yahoo.gr",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "SV1BSX",
    "subject": "[amsat-bb] Re: G-5500 7806 regulator question",
    "date": "2008-08-17T15:48:13Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/43EM2QRGM3SM3A556ICLGOFOHC36JFVV/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hi Mark, Hi all,\n\nanother almost unknown but better and much more accurate combination in \norder to\nincrease the output\nof any 78xx regulator is possible by making a divider in the output of  78xx\nregulator according to the formula:\n\n\nR1=VR/0.02 ( where VR the nomimal output of  78xx regulator)\n\n\nR2=VB/0.025 (where VB the difference in Volts between \"nomimal\" output\nVoltage of 78xx and \"request\" output Voltage)\n\n\nIn  -----------\n---|  78xx   |-----o---OUT\n    -----------      |\n          |            R1\n         o----------|\n          |\n        R2\n          |\n-------o-------------- 0V (GND)\n\n\n\nTherefore, in  case we have a 7805 and we need 6 Volts output:\n\nVR=5 => R1= 5/0.02 = 250 Ohms\n\n\nVB (Differential Voltage):  6 - 5 = 1\n\nR2 = 1/0.025 =  40 Ohms\n\nYou can replace R1, R2 with standard value-resistors:\nR1=220+27 Ohms\nR2 = 39 Ohms\n\n\nThe R1 is connected between + OUT and GND-Pin of 78xx. The R2 between\nGND-Pin of 78xx\nand GROUND (see my figure above).\n\n*** HOWEVER, in this case the Hotsink (metal plate) of 78xx MUST BE ISOLATED\nfrom the 0V !!\nJust keep in mind that,  because the Pin2 is internally  connected\nto metal-plate of 78xx ! So, if the GND(chassis) is equal to 0V and the \nmetal plate of\n78xx is directly connected to chassis for better cooling, then the R2 is \nby-passed\nthrough the internal connection of 78xx. (and the R1 is now just a... \nbleeder !)\n\nFinally, in this combination by using divider (or diodes as mentioned by \nothers)\n the 78xx regulators lose the \"short-circuit\" output protection. That is \navailable\nonly in case where the Pin2 of 78xx is directly connected to 0V (normal \nconnection).\n\nHope this helps.\n\n73, Mak SV1BSX\n\n\n\n----- Original Message ----- \nFrom: \"Mark L. Hammond\" <[email protected]>\nTo: <[email protected]>\nSent: Sunday, August 17, 2008 2:54 AM\nSubject: [amsat-bb] G-5500 7806 regulator question\n\n\n> Hello All,\n>\n> It appears that the 7806 voltage regulator in my Yaesu G-5500 control box\n> has gone bad; the output is measuring more like 10.8 Volts (!).   This\n> explains why both position indicators were off by a factor of 2 (e.g.,\n> elevation meter showing 90 deg, array pointing 45; azimuth meter showing\n> 180 deg, but array pointing 90 deg., and so on).\n>\n> Question---has anybody used a 7805 to replace the 7806 regulator in this\n> control box?\n>\n> I don't have a 7806....so this brings the next question--anybody have a\n> 7806 (or 2) that they want to sell?)\n>\n> Thanks,\n>\n> Mark L. Hammond  [N8MH]\n>\n>\n> _______________________________________________\n> Sent via [email protected]. Opinions expressed are those of the author.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n\n\n",
    "attachments": []
}