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Non-standard 68-pin PLCC socket?

Discussion in 'Datasheets, Manuals and Component Identification' started by TTL, Aug 29, 2014.

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  1. TTL

    TTL

    187
    5
    Oct 24, 2013
    In order to replace a damaged 68-pin PLCC (through PCB hole) socket on a computer's PCB I ordered a new one through eBay and much to my surprise I found the distance between the pin rows to be different! The pin spacing however seems to be the same. Are there multiple standards here, or have I come across non-standard sockets somehow?

    [​IMG]
    [​IMG]
     
  2. TTL

    TTL

    187
    5
    Oct 24, 2013
    By the way, the socket I purchased is a 3M model 8468. I've compared this datasheet (below) with other 68 pin PLCC sockets but haven't been able to find any with the larger dimensions I need.

    [​IMG]
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    The pin spacing MUST be different or the measurements you're seeing would also be the same -- unless you've miscounted the pins.

    I can't imagine that someone would build a custom socket to prevent you from replacing it (it's a pretty gnarly thing to remove) but I also don't know why anyone would deviate from normal pin spacing.
     
  4. TTL

    TTL

    187
    5
    Oct 24, 2013
    I agree and also found that strange.
    I'll recount the pins, but there should be 68 of them (it's for a Motorola MC-68000 16/32 bit processor). I'll also measure the pin spacing again.
     
  5. TTL

    TTL

    187
    5
    Oct 24, 2013
    OK, I've taken a closer look and can confirm that the PCB needs a 68 pin through-hole PLCC socket with 0.1" spacing between the pins. But the row spacing is indeed different when comparing the socket with the PCB holes:
    [​IMG]
    Row spacing on PCB is clearly wider than on the PLCC socket.

    [​IMG]
    PCB row spacing is shown to be approx 23mm (inner) and 28mm (outer).

    [​IMG]
    Replacement socket shows row spacing to be approx 25mm (2.54cm or 1" perhaps? -inner) and 28mm (outer).

    [​IMG]
    The pin to pin spacing however is the same (I tried inserting a row).

    [​IMG]
    PCB next to socket.

    The final photo above reveals something interesting.... the pin count is both 68, but the pin layout is different! :eek:
    Making a custom socket for a standard component sounds weird though :confused:
     
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