HP Forum Archive 20

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HP-67 - polarity of wires to keyboard/display board? Message #1 Posted by BobVA on 13 May 2011, 8:25 p.m. Hi: I was disassembling an HP-67 and the two power wires that go to the keyboard/display board popped out of their sockets before I had noted which goes where. Based on how the wires are arranged it looks like the black wire goes to the upper connector (board oriented with the display at the top) and the red goes to the one below it? I couldn't find a photo that was clear enough to be sure, so if anyone knows or can point me to a reference, I'd be grateful. Thanks! Bob

Re: HP-67 - polarity of wires to keyboard/display board? Message #2 Posted by geoff quickfall on 13 May 2011, 9:39 p.m., in response to message #1 by BobVA HALT!!! Here is a quote from Steve Loboyko's excellent post: 67 posting Quote: Remove the very thick keyboard pad from the middle plastic of the sandwitch. There are two Augat sockets that connect two wires to this board. They are NOT soldered. NOTE THE COLORS OF THESE WIRES AND WHERE THEY WENT BEFORE REMOVING. A MISTAKE HERE COULD BE ABSOLUTELY FATAL TO THE CALCULATOR WHEN REASSEMBLED AND POWERED. I would rather not give you the colors or positions here because this could vary during the production run, but on my 3 67's, the black striped wire was at the top, and the red striped wire was beneath. I personally have had all wiring described as above, but substitute striped for solid colours. Maybe Randy can be more specific on this however Steve is correct. There are many differing production runs and production sites. Cheers, Geoff.

Re: HP-67 - polarity of wires to keyboard/display board? Message #3 Posted by BobVA on 13 May 2011, 9:42 p.m., in response to message #2 by geoff quickfall Thanks Geoff! I'll see if I can confirm that arrangement by doing a little circuit tracing to a known Vcc or ground somewhere. Regards, Bob

Re: HP-67 - polarity of wires to keyboard/display board? Message #4 Posted by Michael de Estrada on 13 May 2011, 10:36 p.m., in response to message #1 by BobVA Hi Bob, I have a schematic that I prepared when I worked on the card reader in my HP-67, and it shows a black negative wire connected to the top right side of the main keyboard pcb and a red positive wire connected directly beneath it. These wires go to the center negative pin on the ac adapter receptacle and the 5vdc positive pin respectively. Michael

Re: HP-67 - polarity of wires to keyboard/display board? Message #5 Posted by BobVA on 13 May 2011, 11:22 p.m., in response to message #4 by Michael de Estrada Mine turned out to be the same arrangement. Thanks very much Geoff & Michael. And I got the card reader to work again! Guess I'll be building a battery pack tomorrow. Regards, Bob Edited: 14 May 2011, 1:37 a.m.

Re: HP-67 - polarity of wires to keyboard/display board? Message #6 Posted by Geoff Quickfall on 14 May 2011, 12:55 a.m., in response to message #4 by Michael de Estrada Production runs change. The caution is 'what applies to one calc may not apply to another.' Anecdotalely, but with no direct evidence, I have been informed that the wire positions have been moved during differing production runs. I have three different coloured wires for power supply in my 65's and 67's from vertical striped to solid. I have yet to see changes in the positioning but have seen that in other boards from other calcs that have undergone revision during production. That is why I say, don't assume they are all identical. Cheers, Geoff

Re: HP-67 - polarity of wires to keyboard/display board? Message #7 Posted by Randy on 14 May 2011, 8:45 a.m., in response to message #6 by Geoff Quickfall It's simple to determine polarity on any classic, any version. The positive terminal always terminates on the left side pad of the power switch. Also, you can sanity check yourself using Tony Duell's excellent crib sheets on all the classics in the archives. HP-67 Internals Edited: 14 May 2011, 8:46 a.m.

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