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Non-standard 68-pin PLCC socket?

TTL

Oct 24, 2013
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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?

68_PLCC_dimensions_zps5c4ee49a.png

68_PLCC_replacement_dimensions_zps46f3a171.png
 

TTL

Oct 24, 2013
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Oct 24, 2013
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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.

3m_8468plcc_zps97c81a1f.png
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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The pin spacing however seems to be the same.

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.
 

TTL

Oct 24, 2013
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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.
 

TTL

Oct 24, 2013
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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:
_MG_9340_zpsf5baee64.jpg

Row spacing on PCB is clearly wider than on the PLCC socket.

_MG_9358_zpsfe6b2719.jpg

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

_MG_9370_zps30688e71.jpg

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

_MG_9336_zps9b69bacd.jpg

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

_MG_9350_zps9aa70752.jpg

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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