![1999 vs 2009 [4032x3024 - 2MB]](https://pic8.co/sh/w8aboz.jpg){kind=link}
Looks like 2009 is missing a 20 pin DIP? Strangely the pads aren't aligned. Or is that a set of contacts for a board test bed? Discoloration on some pads, others look virgin.
To be slightly pedantic ... DIP ... Dual Inline Pins. (So, not a DIP as they are surface mount pads and not Inline...) :)
Your 2nd hypothesis looks to be correct. It's labeled "J1", likely a test / programming connector. Looks like there are pogo pin marks where a fixture came down and spring loaded pins touched the board. Looks like the center hole between the pads is an alignment hole for the header.
Looks like a few of the lower right pins are connected to power buses. Looks like there is some more junk (burned flux, oxidation, etc.) on those pins from the higher current across those pins/pads to power the board while programming / testing.
Just my guess...
2009 had a piece of foam over the top of the components. That's both residue from the foam and corrosion from the interaction between the foam/glue and the chemicals in the environment the drive was in.
Lol! Right, surface mount (if those pads were meant for a device). I never got involved in board test, but that seems like a lot of wasted real estate just for board testing 20 probe pads. I worked at the device level throughout my career, was never involved in board test so I'm not claiming expertise in board testing, just curiosity.
That's a bed-of-nails test point.
That's a bed-of-nails test point.
Nope. It's a board-to-drive interconnect. Notice there are no connectors anywhere on the board to interface with the drive body for the heads, motor or voice coil. That staggered pad arrangement on the board matches up with a springy connector on the drive body which connects to the drive internals. There is a connector at the very top part of the board with four springy tabs that would mate with a PCB contact pad similar to the large 20 pin one which would be on the drive body. That small 4-pin connector is likely the coil drive connections for the three phase BLDC spindle motor. The board is mounted component side down on the drive so there are no connections on the other side of the board. By contrast, the older board has pin headers for making connection to the drive body but also has some springy contacts for the spindle motor coils.
You are right on that one. I had another drive with the same thing that was covered by foam, but that one was not. Just looked at the drive body...or what was left of it, anyway.
I've had at least one drive fail that worked when I cleaned those pads. I often take the PCB off drives and those pads tarnish something awful. I'm guessing they're silver-plated (the tarnish coloration looks like silver does) and usually the pogo pins on mechanism make a gas-tight weld. I take an eraser and clean them all shiny and wipe the pogo pins before I reassemble, for good measure.
Ahah! Seems to me (with no board test background) like a lot of wasted board space dedicated to 20 probe pads.
Not really, the manufacturer has all of the space on back of the drive to place board, and there's no real cost. I doubt you could measure the financial impact of that little bit of board over the entire run of that drive.
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