Re: 1/2 HP-11C display Message #4 Posted by Duane Hess on 18 Aug 2012, 4:53 a.m., in response to message #1 by Duane Hess
Thanks Umgawa/Randy.
Checked the items you mentioned.
The zebra cables have been interchanged, flipped end to end and rotated thereby exchanging which side hits the PCB. The display was tested after each of the 3 movements. No difference.
Looking down the display from each end and noting landmarks on the PCB & also carefully lifting the display shows the black portion of the cables probably are hitting the pads and sitting square to the PCB. Also there are water marks in the gold pads where the black part of the cable hits. Those marks correspond with the visual examintation. The top cable hits the pad almost in its entirety. The bottom cable is about 1/2 the black part below the pads, but don't appear to hit anything else. This visual appearance appears consistent across the entire length of the display (top & bottom).
Measured the voltage on the pin you mentioned. Presumed pin 1 was by the dot on the IC package and went counter clockwise. The chip has two groups of 12 pins along the bottom edge. Pin 16 has +1.2V. Turning the unit over the leftmost pads top & bottom join together and lead to a feed-through hole in the board. The pads & hole all have the same voltage. Removing batteries & checking continuity between the hole and pin 16 shows continuity (about .1-.2 ohm).
I did notice on the chip that pins 22 & 23 appear soldered together, I have no idea where they lead.
I have done the press & hold power, X (multiply), release power, release X and it goes through the self-test. You can see "running" (all segments) if you press on the retaining bracket evenly. The test pattern results in most segments lit up correctly. Yet a backspace and entering ten 8s show only the right 5 digits. (no matter how you press on the bracket)
??? is there something different that lights up the display during the self-test as opposed to the normal display of digits?
A consistently repeatable pattern is produced. The 1st digit shows the bottom and middle segments along with the upper right. I'll denote it with a V. The 6th digit is like a capital G (all segments but middle & upper right). Positions 2-5 show as a capital A (all segments but the bottom one).
test results:
-V,A A,A A G,8,8,8,8,
the annunciators are Grad D.MY C Prgm.
??? even though the self-test shows G in position 6, that digit lights up as 8 if you enter enough 8s
Just curious what this means.
thanks
Edited: 18 Aug 2012, 4:57 a.m.
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