|Re: HP-27S needs helps !|
Message #3 Posted by Randy Sloyer on 24 Jan 2003, 10:31 a.m.,
in response to message #1 by Pyerre
If it has been disassembled before, it is possible that the circuit board was not fully compressed onto the rubber zebra lcd strips before the twist tabs where turned, resulting in loose connections and missing lcd pixels. Or, one other possibility is that the zebra strips had been removed, then reinstalled upside down.
I would disassemble and carefully clean the zebra strips and lcd contacts with isopropyl alcohol, then reassemble. The zebra strips should be blue/black on older machines, white/black on newer ones. The black sides face the center of the lcd.
Straighten the tabs so the pc board drops on, center the board on the tabs and press in the center between the top and bottom row of tabs, then re-twist to seat. I always use this order for the tab re-twist:
Bottom left - Bottom right -Top center
Top left - Top right - Bottom center
The order is important since the bottom left and right side tabs have small nubs that center the circuit board on the frame. Always press on the pc board below the tab you are seating.
Just be careful with the six twist-tabs. You'll only get about 5 or 6 tries before they fracture.