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black wires together rule???

Discussion in 'A+' started by damo101, Mar 2, 2006.

  1. damo101

    damo101 Byte Poster

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    Just wondering if anyone else came across this rule - haven't seen it myers (spotted in some A+ thing in work that seems to be too simplistic - makes every PC sound like is made of Lego!) -

    Know the “black wires together” rule. When you’re attaching an AT power supply to a motherboard, the connector will be in two pieces, P8 and P9. These must be oriented so the black wires on each connector are near the black wires on the other connector. Otherwise, damage to the motherboard could result

    Apparently this is in the Exam Essentials so no harm in understanding it then I suppose!

    Cheers guys,

    Damo
     
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  2. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    This is well known for the old AT plugs. It is in Meyers all in one, in my copy on P 306.

    Harry.
     
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  3. damo101

    damo101 Byte Poster

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    cheers Broom,
    i'll bust out the Myers book once i get home from work.
     
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  4. Malnomates

    Malnomates Megabyte Poster

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    just remember to keep the black wires together when plugging in P8 and P9 (centre of the pin array).Theres little else you need to know regarding the P8 and P9 rule really,other than AT power supply voltages.
     
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  5. Lord Deckard

    Lord Deckard Byte Poster

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    See, a sample fact that I knew that yet again didn't crop up on my A+ exam but your experience may be different LOL!!

    Lord Deckard.
     
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  6. Smiten

    Smiten Bit Poster

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    well im glad that my mike meyers book explains the two power connectors hell :gun l.
     
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  7. Bluerinse
    Honorary Member

    Bluerinse Exabyte Poster

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    It's a rule that is worth knowing but it makes me wonder why they have two identical sockets right next to each other in the first place. Surely it would have made some sense to either use sockets of a different shape/type or colour code them so that people would not confuse them.

    Poor original design IMHO.
     
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  8. Baba O'Riley

    Baba O'Riley Gigabyte Poster

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    Is there a reason that there are two sockets anyway? Why not just make it one large socket?
     
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  9. twizzle

    twizzle Gigabyte Poster

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    OK i have no idea why 2 connectors were used instead of 1 larger 1... all i can think of is that a long connector might be harder to remove than 2 smaller ones.

    However i did find this....

    Alright, enough with the preamble. Let's look at the connectors, starting with the oldest style. The PC/XT, AT, Baby AT and LPX form factors all use the same pair of 6-wire connectors, usually called "AT Style" connectors. They are typically labeled either "P8" and "P9" (what IBM originally labeled them) or "P1" and "P2". (Actually, the PC/XT form factor omits the +5 V signal on pin #2 of P8, but otherwise is the same.)

    The biggest problem with the design IBM used for these power connectors is simply the fact that there are two of them and they are the same size and shape. The connectors are physically keyed so they cannot be inserted backwards, but it is very possible to accidentally swap them. If you do this, you will be putting ground wires where the motherboard expects live power and vice-versa, and the results would be catastrophic. Thus, technicians working with older systems developed the well-known mantra: "black wires together in the middle"!

    Starting with the ATX/NLX power supply, Intel did away with the potential P8/P9 risk by making the main connection a single piece, and using only dissimilar shapes on any other connections between the power supply and motherboard. These are called "ATX Style" connectors. For its regular power supply connection, ATX uses a 20-pin connector with a square hole for pin #1 and round holes for the other 19 pins.


    From here http://www.hardforum.com/showthread.php?t=756864

    This thread has loads more on the Tech specs of PC PSUs if u can be bothered to read it all... But from what i can remeber of my A+ all i had to know was the voltages present on the connectors and that they sat, as mentioned, Black to black (ground to ground to prevent possible shorts!).
     
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  10. Baba O'Riley

    Baba O'Riley Gigabyte Poster

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    Nice info there Twizzle. Thanks. :thumbleft
     
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  11. twizzle

    twizzle Gigabyte Poster

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    :) i tries me best lol... Well as im not working i have all the time in the world to look for useless, i mean useful, pieces of info onthe net.. beats doin housework!!
     
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  12. Bluerinse
    Honorary Member

    Bluerinse Exabyte Poster

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    LOL - you should be studying your N+ twizzle :cheeseyg
     
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  13. twizzle

    twizzle Gigabyte Poster

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    I am i am.. Gimme a break lol.. been studying for n+ none stop for last 3 weeks.. still cant get the damn OSI into my head...

    Plus im looking for exam vouchers on the net... and i like to help ppl :)

    Now back to city of heroes and my lvl 41 toon.. i mean back to n+ study!!
     
    Certifications: Comptia A+, N+, MS 70-271, 70-272
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