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HP34C solderless chip orientation
07-16-2021, 05:02 PM
Post: #1
HP34C solderless chip orientation
I recently came across a 34C that I'm trying to get working. It wouldn't turn on at all at first, but I've now got it to the point of near-fully functional.
I'm not sure if I've induced the problems I'm seeing, but when turned on it displays Pr-error, and the self test returns an error 9. I saw a post on line suggesting a chip may be in backwards (one fell out during disassembly). I oriented it the same as the other two, but maybe that's not correct. I've also found that I cannot enter a decimal point, but I can enter Pi using the same key preceded by the black h key. Obviously the key works, so maybe that's further evidence of a backwards chip. What is the proper orientation of the three small chips? I'd like to keep the openings and disassemblies to a minimum.
Thanks.
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07-16-2021, 06:39 PM
Post: #2
RE: HP34C solderless chip orientation
This link has some pictures inside a 34C

https://archived.hpcalc.org/museumforum/...16753.html

cheers

Tony
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07-16-2021, 06:49 PM
Post: #3
RE: HP34C solderless chip orientation
(07-16-2021 06:39 PM)teenix Wrote:  This link has some pictures inside a 34C

https://archived.hpcalc.org/museumforum/...16753.html

cheers

Tony

JeffM:
Notice the white/yellow dots on the chips in the first 2 pictures in that link, that indicates the end of the chips that has Pin 1 (in those pictures #1 is on the upper right corner of the chips). Note that all 3 chips are aligned with the dot on the right (toward the far edge of the calculator when it is in position for use)
Pin 1 may also be indicated by a small dent near in the epoxy near the pin, or at the same edge of the chip as the dot is in the picture.
I hope Tony and I have helped.

The internal photo for the 34C in MoHPC (https://www.hpmuseum.org/30comp.jpg) only shows 2 chips... can someone fill me in on that? B)

10B, 10BII, 12C, 14B, 15C, 16C, 17B, 18C, 19BII, 20b, 22, 29C, 35, 41CV, 48G, 97
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07-16-2021, 08:22 PM
Post: #4
RE: HP34C solderless chip orientation
Hi,
Thanks for the help. I've attached a picture of how the chips are seated, they are all the same orientation though one doesn't have the dot. I guess the next question is, did I get them in the right positions?    
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07-16-2021, 09:08 PM (This post was last modified: 07-16-2021 09:08 PM by teenix.)
Post: #5
RE: HP34C solderless chip orientation
(07-16-2021 06:49 PM)Ren Wrote:  The internal photo for the 34C in MoHPC (https://www.hpmuseum.org/30comp.jpg) only shows 2 chips... can someone fill me in on that? B)

3 chips.

2 x ROM/RAM chips and 1 (larger) Processor.

There is 8K of ROM and 48 RAM registers in the 34C.

Most likely 4K ROM and 16 RAM registers in each.

I think there is some RAM also in the processor chip because the RAM map uses 48 registers.

If the ROM chips don't support 4K then the extra must be also in the processor chip.

cheers

Tony
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07-16-2021, 09:17 PM
Post: #6
RE: HP34C solderless chip orientation
I think Ren was referring to only the 2 smaller ones. Some versions have 2 and some have three. One is ROM for the C (constant memory) and the other two are RAMS. The ROM has a different numbering on the case and the RAMS have a similar numbering. This thread has more info (https://www.hpmuseum.org/cgi-sys/cgiwrap...read=24353).
I swapped the two RAMS and it made no difference, so maybe one is just faulty.
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07-16-2021, 09:28 PM
Post: #7
RE: HP34C solderless chip orientation
Well, it appears I lied. Swapped the RAMs back where they were, got it all back together, the bottom edge of the bottom case felt a bit loose (under the HEWLETT PACKARD 34 C label), snapped it in tight, got some odd double-zeros in the right-most two digits of the display, ran STO - ENTER and the display lit up full, now the decimal works and there's no Pr-error when turning on. We have ignition!
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07-17-2021, 04:29 AM
Post: #8
RE: HP34C solderless chip orientation
I didn't think the ordering of the smaller chips mattered in the 34C.
Just their orientations.

Pauli
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07-17-2021, 09:37 PM
Post: #9
RE: HP34C solderless chip orientation
The ROM has to be closest to the display (I even tried swapping it into another spot just to see what would happen, because it and one RAM had an orientation dot but the other RAM didn’t). The two RAMs supposedly don’t care which position they’re in, but another thread mentioned someone swapping them, making no difference, and then back again and it solved his issue. It shouldn’t make a difference but for some reason, did.
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07-18-2021, 03:52 AM
Post: #10
RE: HP34C solderless chip orientation
(07-17-2021 09:37 PM)JeffM Wrote:  The ROM has to be closest to the display (I even tried swapping it into another spot just to see what would happen, because it and one RAM had an orientation dot but the other RAM didn’t). The two RAMs supposedly don’t care which position they’re in, but another thread mentioned someone swapping them, making no difference, and then back again and it solved his issue. It shouldn’t make a difference but for some reason, did.

Probably means a bad connection that "fixed" itself during the movement.

cheers

Tony
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