HP 2100A Restoration

[Jay West]

Hayden wrote....
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I've also got two additional boards in a bag that I haven't taken out yet https://goo.gl/photos/D4quXT992Y6huQoAA . They're in there quite tightly, but I did take a peek at some of the chips that I could see from the edge.
Couldn't read the part number, but they were Intel chips and almost looked to me like they were early static ram.
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I can't make anything out from that picture. One word of caution - HP intended the handles to be color coded to at least show what area they should plug in to on the 2100. Do not take that as absolute. I have seen first-hand where users replaced a broken handle with whatever color they had spare. Also, color coding on the 21MX (where I/O cards are interchangeable with the 2100) was not necessary and not always done. Moving those back to a 2100 could make you think the wrong thing if you follow handle color blindly.

And....
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If they are I know it might not help with testing the memory but might help with making sure the CPU works first. Not sure which slot though they'd install to even if they were, I'd presume the white slots.
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I am not super smart electronics wise, I'm a neophyte. But I can't comprehend any way that sram could be used in that card cage. Let me give strong clear warning.... do not plug any board into any slot unless you are 1000% sure that it is supposed to go there. You WILL let out the magic smoke. With very few exceptions, most of those slots are wired differently and expect certain things to be plugged in there. As I recall, the memory section "power in" pins carry enough current to create a permanent glitch. 

And....
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For the memory test I don't see any (visible) front panel switches that would indicate a memory test, the ones that I can see just look like they're for direct depositing into core. But I'll have to check the manual for that.
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To see the switches I am referring to - you will have to take off the white bezel around the front panel. 4 hex head bolts, two on each side, about 1/2 inch back from the front. HOLD the bezel when you take out the screws so it doesn't fall. It's not going to break, but may break whatever it falls on. Also, pull it forward, and don't let it slide down (the wire wrapped "edge card" pins are at the top, you don't want the bezel to hit them). And again - as I recall the switches weren't specifically for a memory test. I think they were to assist in clearing memory. One of them may have made microcode singlestep... I think there were at least 2 and maybe 4 slide switches under the panel. See operators guide :)

J