Weird circuit part 2

Well, I have got the board all powered up (I found “G” and “5V” silk screen markings hiding under one of the headers) and I think I have mostly figured out all the jumpers. There are two jumpers which I have called X and Y and the rest of the jumpers I have divided into sets R and S. The segments of the SSD I will refer to according to the following diagram from Wikipedia, with the leftmost digit being digit one and the right most digit being digit 3.

The jumper sets R and S are as follows:

Header set R

Header set S

Jumpers X and Y are found here:

Using Karnaugh maps, which I always find fun, the X and Y jumpers can be used to enable/disable header sets R and S.

__|X|~X|                 __|X|~X|
Y |0| 1|                 Y |0| 1|
~Y|1| 1|                 ~Y|0| 0|
Map for header set R     Map for header set S

This simplifies to R = ~X + ~Y and S = ~XY (ie. set R is enabled when either jumper X is removed OR jumper Y is removed and set S is enabled when when jumper X is removed AND jumper Y in installed). At first I thought that this setup might be so they could plop a bunch of headers in and be able to just swap around the X and Y configuration to get different readouts, but I don’t really see that being feasible with how this is all setup.

There are also a bunch of headers that don’t seem to do anything (every fourth set in the top and bottom rows). Perhaps it was just cheaper to install a wide set of headers than to install a few broken sections. Having set R spaced at every other header makes it easy to place jumpers so a dead space does make sense. There are traces I can see to some of these pins, but I suspect they are just grounded so that they don’t light anything. There is also a pin missing just above the X header. On the back side of the PCB you can see there is a via almost in the spot where the header pin should have been, but not quite exactly. If they really put the big headers in to save money/time, why pull this pin out of the header block? The via would have worked just as well if there was a pin soldered in the hole. The via connects from common B1 pin to the SSD, so that pin was likely removed to prevent the B1 segment from being lit by a jumper near X.


Weird circuit

So a couple days ago I was tearing apart a bunch of old computers I had kicking around, pretty much just a bunch of PIIs and older. I figure they aren’t really of much value used as originally intended, but I don’t want to see them end up in a land fill or piled up in someones backyard in India, so I’m stripping them down for components for electronics projects (if anyone needs any older computer parts (including CD-ROMs, floppy drives, power supplies, sound cards, CRT monitors, etc.) or components they suspect would be on an old motherboard, feel free to drop by).

Anyway, I pulled this one PCB out of the front of a computer that seemed a bit odd. All there is to it is a triple digit seven segment display, a single resistor (I suspect to regulate power to the display), and a huge amount of jumper pins. I think I count almost 100 pins. The thing faces out through the front of the computer case, I assume as a CPU frequency display (an older computer we used to have had a similar thing). What weirds me out is that I don’t recall there being any cable connected to this thing. I wasn’t really being too careful when disconnecting headers from the motherboards, but I really don’t recall ever unplugging this thing. Even if I had unplugged it, the majority of these pins look like they are just jumpers. There are two small 2×5 sections of pins that I suppose could have been headers for some other connector, but I don’t really see the necessity of all the jumpers.

Update: I have got the display powered up and played with the jumpers. Che out the new post.


A Computer Virus

I just found this weird UK short film. Quick synopsis: a guy gets dumped which spawns a computer virus that destroys the world. Oh ya, I almost forgot; it’s a musical.