From: delphys@ocean.cc.mcgill.ca (David Holmes)
Newsgroups: comp.sys.hp48
Subject: The interior of the hp48sx revealed... (and still working!)
Keywords: prying, hood, Im-not-dead-yet
Message-ID: <1992Jul2.000843.27782@sifon.cc.mcgill.ca>
Date: 2 Jul 92 00:08:43 GMT
Sender: news@sifon.cc.mcgill.ca
Organization: McGill University Computing Centre
Lines: 104
Nntp-Posting-Host: ocean.cc.mcgill.ca

Well neat-o...

	So I took Joel's (kolstad@cae.wisc.edu) suggestion anyway:

>Drill them out and tell us what happens. :-)

	and did just that.  I was however somewhat correct in my  
assumption about those little rectangular holes (the ones which everyone  
pointed out were for the templates; ok I'd forgotten about that use!)   
There are some naughty little metal hooks that you could probably get at  
via the little rectangular holes given two things (ya I know just like  
fine print isn't it... well no pain no gain!)  First you'd have to know  
they were there ;-) and second you'd need some sort of tool, a bent, stiff  
hook or something, to allow you to push the case (lower half) off and  
around the hooks.  As it was a bit of persuasion was all that was  
required.  All of this was of course after a bit of drilling (the ten  
plastic mushrooms: 4 at serial port end and six amoung the keys.)  I am   
not too worried by this drilling as I am fairly certain that a bit of  
modification to the holes (beveling) and some counter-sunk screws will put  
the thing back together (if rubber bands won't do ;-)

If anyone is interested we have one of those little Scanman dohickies here  
at work so I thought about trying to take some interior shots and turn  
them into GIFs.

Anyhow on with the show... oh and yes it _does_ still work (its running  
now via wires and alligator clips to the batteries)...

	There are 4 plastic and standard ICs and the CPU.  The 4 plastics  
consist of two LCD (if memory serves) controller/drivers SED1181F, what is  
probably the memory: M5M5256BFP, and the fourth, a NEC part, with which I  
am unfamiliar: three rows of numbers:

1818-4891
F62
9048EP002

Perhaps a memory and/or bus control chip for the slots (?) (anyone else  
got NEC parts books?)

The CPU is rather neat.  Between the two screen chips is what appears to  
be a ceramic wafer about 2cm X 3.5cm or 7/8's X 1 & 3/8's inches. In the  
centre of this is the chip itself, not quite square but about 1/4 inch a  
side.  Running out from the chip on all four sides are the leads (about 56  
down each long side and maybe half that one each short side.)  Off to one  
side, on the wafer, is a little teeny-tiny hp logo, but I'm only guessing  
as it is just about too small to make out!!  

The whole arrangement is rather nice as taking the '48 apart does not  
throw half a million little keys all over the place.  The keys themselves  
are part of the upper half of the case and the contact surface is  
underneath a piece of sheet metal which _is_ just about welded in place  
(lots of little plastic mushrooms.)  This sheet metal by the way is also  
the NEGative battery terminal, the home of those naughty little hooks, and  
in running the length of the machine, the thing to which the PCB (printed  
circuit board) is mounted.  The PCB appears to be two sides only (ie not  
multilayer.)  It is not masked (the green solder mask some may be familiar  
with) but rather looks to be 100% gold plated.  A really beautiful board:  
nicely laid out and well made.  To my way of thinking, typical hp quality.

The card slots exist as a single piece of molded plastic with the stylized  
letters DDK in a oval all in relief on one side.  Again good workmanship.   
One thing that was not apparent from looking in through the card slots is  
the set of advanced contacts (the sides of the cards would contact these  
about 1cm before they came into contact with the pins) on each side of  
each slot.  It is hard to tell whether or not they are used electrically;  
they do _look_ to be connected to a trace on the underside of the PCB but  
I cannot as yet get a clear view (my multimeter would help.)   
Interestingly the slots seem to share most of their pins (ie soldered to  
the same pads on the PCB.) The pins that are not shared are numbers 2, 3,  
4, 20 and, 39 (my scheme: there are 2 rows of 40 pins numbered 1 to 40  
with 1 being on the left if the '48 is keyboard-up and you're looking into  
the card slots from the serial port end (top) of the machine.)  Does  
anyone know whether or not hp follows the memory card standard (the  
acronym of which escapes me at the the moment?)  I don't recall whether  
this has already been established in c-s-hp48 .

The bottom half of the case is empty but for the piezo buzzer and the  
reset switch.  This latter is actually part of a complete front to back  
piece of sheet metal (also connected to the NEGative side of life) which  
also provides some shielding I guess.  The buzzer's other contact is a  
coil spring (much like a negative battery contact in a flashlight) that is  
soldered to the PCB.

Well thats all for now and it was kind of fun!  Now where is my  
oscilloscope ? :-)  Oh yes if anyone has any info on the NEC chip I'd be  
very interested (actually further info on any of them would be welcome.)
One final note: I will be happy to explain in more detail exactly how I  
got my '48 apart if anyone really cares. And of course because we live in  
the world we live in I have to include the following: "I do not recommend  
that anyone listens to or acts upon anything that I appear to have said; I  
don't speak for my employer and they don't speak for me; everywhere you  
go... there you are; and of course your mileage may vary depending upon an  
infinite number of inexplicable factors."

David

--
________            __________________________                 __
        David Holmes                          McGILL UNIVERSITY
UNIX Support Group - Computing Centre         Montreal,  CANADA
email/NeXT email  delphys@CC.McGill.CA       voice  514-398-3716
                  delphys@MCGILL1.BITNET     FAX    514-398-6876
-----------------------------------------------------------------
