The Museum of HP Calculators

HP Forum Archive 15

[ Return to Index | Top of Index ]

32SII Repair
Message #1 Posted by Neil Thomason on 17 July 2005, 8:34 a.m.

After following 32SII deconstruct instructions I am now at the reconstruct stage, however I did not take note of the "Zebra stripe's" orientation and a gut feeling tells me this is can be a show stopper.

The "zebra stripe" is one of the 2 the rubber spacers located between the LCD and the PCB. Its footprint matches the pinouts on the PCB and it may act as a ground or something.

if any one out there has useful info. Please advise

      
Re: 32SII Repair
Message #2 Posted by John Limpert on 17 July 2005, 12:44 p.m.,
in response to message #1 by Neil Thomason

Zebra stripes are use to connect signals between two assemblies, like a main board and a daughter board. They are composed of alternating sections of conductive and non-conductive material, hence the striped appearance. If you look at the signal contacts on each assembly, the placement of the zebra stripe should be obvious. Each dark section of the zebra stripe behaves like a jumper wire, connecting the adjacent contacts on the assemblies.

            
Re: 32SII Repair
Message #3 Posted by Neil Thomason on 17 July 2005, 3:42 p.m.,
in response to message #2 by John Limpert

Thanks John, I suspected somthing like this but what threw me was no signal when I dropped my tester along the dark stripe.

Best regards nth

                  
Re: 32SII Repair
Message #4 Posted by Neil Thomason on 17 July 2005, 4:02 p.m.,
in response to message #3 by Neil Thomason

P.S. I am assuming Dark side faces PCB

            
Re: "Zebra stripes"
Message #5 Posted by Paul Brogger on 18 July 2005, 12:11 p.m.,
in response to message #2 by John Limpert

I've only seen the "Zebra stripe" appearance in those from the earliest LCD calculators (not necessarily H-P) that I've disassembled. The most "zebra-like" examples I remember were strips of mylar (perhaps) with parallel conductive traces, wrapped around a squishy rubber core.

Later versions are rubbery (insulating) strips with conductors somehow embedded. In my experience, there isn't necessarily an obvious color coding to indicate which sides are conductive. Neither is it easy to determine with a multimeter, as the conductors themselves are tantamount to individual, fine wires, and it's hit-or-miss when you're trying to touch both sides of the thing with probes.

Also, while orientation is all-important, alignment isn't necessarily an issue for the later types. The pitch of the conductor grid being MUCH finer than that of the PCB/LCD contacts, when placed in approximation, correct connection of the various pads is virtually guaranteed, regardless of the left-to-right alignment of the conductor strip itself.

FYI

                  
Re: "Zebra stripes"
Message #6 Posted by Neil thomason on 18 July 2005, 8:18 p.m.,
in response to message #5 by Paul Brogger

Hi Paul,

Repair now completed and tested, correct orientation for the zebra stripes is as follows:

Upper spacer dark stripe against LCD with white facing top of calculator Lower spacer dark stripe against LCD with white facing bottom of calculator

Thanks to all


[ Return to Index | Top of Index ]

Go back to the main exhibit hall