|Re: Pioneer internals|
Message #3 Posted by Larry Holmes on 19 Aug 2006, 2:56 a.m.,
in response to message #1 by Speck
I happen to have a deceased 42s which I paid a LOT more than $5 for, with a good lcd screen. I planned to repair it, but this one was a kind of a scam, as I learned quite a bit later, when I decided to open it up to fix it.
I found it had been previously opened; the chip leads were broken in several places, and it was then very well put back together, as though someone had tried to probe the chip leads or something; they are so tiny and thin, it would be impossible to do anything with them but destroy them unless you have a precision-made probe head or similar, which is similar to the equipment HP would have used to test defective pc boards with chips on them, and thus, not a trivial piece of gear..... and even if you did discover the chip was dead, or which part of it was dead, what would you do then? There is NO WAY a standard human being could re-work this pc board by hand; it is just too dense and microscopic; so I can't imagine what was done to it.... or even more mysterious a questions is: WHY BOTHER TO PROBE IT IN THE FIRST PLACE? The pc board doesn't have much on it except for one chip with about a "zillion" leads coming out of all four edges, which were attached to the pc board by tiny technician fairies who worked for HP at one time (or perhaps, an automated assembler..) ; couldn't tell it had been opened until I got into it, and it was too late to do anything else with it.
Whoever did all this must have been uniquely foolish, dumb and stupid! There certainly are much simpler scams to work than this one!
Anyway..... it does have a known good display. I would be willing to work out some kind of "deal" to make one good one out of the two, for one or the other of us to cherish for years to come (I would guess you would want to keep yours, but I'd be willing to discuss buying it if you'd like to sell it "cheap"!!) I should warn you, though: replacing these screens is not the easiest thing in the world to do. There are some not-so-obvious things to do and to watch out for, and the pc board is extremely "delicate" and vulnerable, more than others in HP's earlier calculators; because of all the power of the 42s, it required a very powerful and dense chip to contain it all.
Even though it is going to make this message very long, I thought I might describe some of the steps required, so you would know whether or not you wished to attempt to do it.
One example of a step which is not readily apparent: the LCD glass substrate is connected to the calculator's pc board with a "zebra" strip connector, which is a rubber strip about 2-3 mm square and about as long as the lcd; looks a bit like a square "worm" or tiny square-sided snake. Each strip has alternating conductive and insulative portions which are light and dark in color, similar to the stripes on a zebra, hence, the "zebra" nickname. There is one at each edge of the LCD; it is not glued or otherwise attached, it is held in place by pressure after the lcd and pc board are securely mounted. So, it must be sandwiched between the lcd and the pc board precisely, so the contacts on the lcd and the pc board are electrically connected by one or more of the conductive bands when the strip is compressed between them. The lcd and board must be aligned so their contacts would line up if the lcd and the pc board were to be pressed together. This is made more difficult than it may sound by the fact that the contacts on the lcd are almost transparent; they are only visible to the naked eye when held at just the right angle to the light, and, by the fact that the lcd is only held in place by adhesive strips, similar to the ones used to hold the front panel on the calculator (or, similar to double-side scotch tape); the first time I did this repair, I expected that I cold simply put the lcd precisely where the old one was and that would be enough, but, it didn't work (???); I had to use "trial and error" placements until I got it all right, and there were many "T&E's".
Once the two zebra strips are properly positioned and the lcd is in place so it will line up with the pc board contacts (there are perhaps 80-100 of them, total; not sure as I have never counted them!), you must position the lcd on the metal plate to which the major parts of the calculator are physically attached, and press it into place so that the adhesive will hold it there "forever", but not so much as to break the lcd glass (or chip or crack the edges, which are the electrical connectors, made by plating a transparent metal onto the glass when the lcd is manufactured; you'll know what that means if you are familiar with lcd's; in fact, I am probably telling you what you already know everywhere here, but what the heck, I should put down as much as I can think of right now, you can ignore what you already know!).
Once you are certain you have the lcd properly positioned and attached to the metal plate, you must put the pc board in position over several metal tabs which you bent out of the way when you removed the pc board, without disturbing the placement of the zebra strips or the lcd. The tabs are then bent back into position, so there is enough pressure to force the pc board contacts down onto the zebra connectors sufficient to insure electrical contact but not enough to cause any damage (this isn't really that hard; it is actually more difficult to get ENOUGH pressure than too much, unless you modify the way the tabs are made and bent, etc.). There is also a rubber pressure strip which presses the thin plastic sheet which carries the keyboard connections against the pc board, which must be in place and must provide sufficient pressure to cause the keyboard contacts to electrically connect to the pc board as well.
Once that is all done, and if you have done it correctly, voila! Yougotchyerselfanewcalculator! (hahahaha! German word structure using english words!) If any of it is not right, though, you get to start over again. You have to be careful not to bend the metal tabs too many times or they will break off.
Not trying to "scare" you with this description, however, I know of a couple people who mangled their costly 42s calcualtors by trying this when they should not have. If the above doesn't really worry you, you're probably OK. If it doesn't sound very familiar, best to find someone who has some experience with it. I wouldn't call it my favorite thing to do even though I do have experience with it! But, the potential reward is worth the tediousness of the work....
If you'd like to discuss possibly melding our two 42's into one, whichever way it works out for one of us to get to keep it, let me know; you should be able to get my email address here as I have not specified that it be kept private. I'm not out to make a bunch of money on this; I hate to have the dead 42s sitting around here if I could use it to help someone else as I have often been helped by others on the internet. I'd want to either have a chance at being the final owner, or, if that isn't feasible, to cover my costs in process; no profit taking is required.
Hope to hear from you.
hmmm... this isn't very well written; should I send it or delete it? I'll figure that out later.... how did it get so LONG?