11c questions

HP amigos-

Please, if you'd assist a pitiable rube like me who still tries to fix old, "junky" calcs...

Question number 1- how many chips do you see when you open the 11c? There are two sets of internals -- I'm asking about the newer one, I think. S/N 2538A.....

I'm pretty sure there are two chips, one rectagular 2:1 and one square, with a locus of unused connectors in between them.

If this is correct -- 2 chips -- then the favor is this: can you send me a high-res, very close up pic of the left-most, larger chip?

I specifically need to see, in ultra-high relief, the connectors toward the bottom side of the calc. This one I'm trying to fix has two connectors, the 2nd and 3rd from the right end, which appear to be soldered together.

NB: If you're kind enough to oblige me do please remember to be careful about the two tiny springs when opening the case.*

The unit is DEAD (tried shunting, holding power button on for 60s, etc). And in excellent condition (the only thing keeping me from writing "mint" is that it's not still shrink-wrapped). I'm thinking it's possible it may never have worked, given the lack of any wear at all. Could its death be the result of too much solder during manufacture shorting these chip connectors?

Any advice further, related, etc. most welcome.

*Thanks to Luiz for useful discussions on HP11c repair from 6(!) years ago.

Edited: 10 Mar 2008, 1:17 a.m.


Any help? Anyone? Randy -- you have got know the answer to this one.


Hmmph. I guess I've done it again -- some egregious offense to the entire HP calc repair community of which I'm sadly, but typically, unaware.

I'm just going to go ahead and nudge those apparently errant soldered chip leads with a hot soldering iron, free them from their hopefully unintended shackles and pray that the bastard fires up when I reassemble it.

I'm sure you're all waiting with baited breath.

If I get it working, I vow to sell it. Coburlin-style, on Ebay.

(I wonder what the record is for single contributor threads anyway.)


Geez, you need to get a bit more thick-skinned about the Internet. Maybe the reason you didn't get replies is that we don't have what you asked for. I certainly don't. I've got some photos of the innards of a few variants of the 12C, but not as sufficient resolution for what you are asking.


Mark --

Well, you might be in luck. I just happen to be doing more some "Voyager speedup" work, and opened up an early 1985 HP-11C (S/N 2508Axxxxx) that I'd modified three years ago. I even took some digital photos last night for this effort that may meet your needs.

I'm pretty sure there are two chips, one rectagular 2:1 and one square, with a locus of unused connectors in between them.

That's exactly correct. The larger (rectangular) one is a 1LE2-0323. I see the 3rd and 4th pins from the lower right corner soldered together; they don't seem to be connected to anything on the circuit board. The square chip is a 1LF5-0301.

I also have an HP-15C from late 1985 (S/N 2543Axxxxx) opened up. It has three chips, which are different:

1LH1-0306; 1LH1-0302; 1LM2-0001

1LF5 and 1LM2 are the CPU chips, according to info from Ken Sumrall in Eric Smith's web page on the topic:


Shortly, I will open up a 1986 HP-11C (S/N 2624Axxxxx).

Post an e-mail address (anti-spammed as necessary), and I'll send some photos directly. I don't have image hosting set up.

-- KS

Edited: 12 Mar 2008, 12:53 a.m. after one or more responses were posted


Hey Eric -- that's good advice -- not for internet-only application, either.

I guess I have to work on my delivery too. Apparently the good-natured self-depracating sarcasm didn't transmit.


Hi Karl -- thanks! And that was pretty savvy letting Eric post first so as not to break the longest single-contributor thread in recent memory.

Hmm. Third and fourth, not second and third? That is interesting. Either I have screwed up or the plant did. More likely me, I'm guessing. I'll have to go over it again.

Thanks for the photo offer -- pb120669 verizon net.


Hmmm... I think I usually have a reasonably good sarcasm detector (and can certainly dish it out), but apparently today it failed me.


Coburlin-style? On Ebay?

I'd hoped at least to elicit a chortle with that one.

I haven't managed to fix it, btw. I did move the solder joint but to no avail.

Now the question is -- go forward and pry off the main circuit board? Ugh.

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