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HP-67 not behaving?
07-27-2022, 06:03 AM
Post: #1
HP-67 not behaving?
Hi - I’ve had my “best” 67 in a drawer for a while and I decided to use it today after months (a year?). This machine was professionally restored about 10 years ago and is in mint condition. I popped in a battery and plugged it into an USB charge cable from TAS some years ago (that I have used with this 67 many times). It powers up but is not working properly. I hope it’s not dreaded ACT-itis (since my power source is 5V?). Here are the main symptoms (100% repeatable):

- display is permanently in SCI mode with DSP = 0 (only 1 digit of mantissa visible, decimal point, and 2 digit exponent)
- any numeric digit entry gives a display of “-x000000000. 00” (x = 0..9)
- stack lift ops (ex. ENTER) appear to correctly enter single digit into stack (without the minus or the extra 0s)
- arithmetic operators appear to work (single and dual operand) although display remains in SCI DSP = 0 mode
- stack can be rolled and remembers all 4 entries
- primary registers STO and RCL correctly
- PROGRAM mode shows “000” and nothing changes it (entries, SST etc)

Ideas????

Thanks

Mark
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07-27-2022, 10:09 AM (This post was last modified: 07-27-2022 01:58 PM by teenix.)
Post: #2
RE: HP-67 not behaving?
I did some experiments with my 67 emulator and if I fail the RAM at addresses 48 to 63 and only read 0's from this memory range, then I can recreate your problem.

It seems like the RAM in this address range has failed. I'm not sure which ROM IC this RAM belongs to as I haven't had a chance to read the 67 ROMs and run RAM tests for real yet.

Sorry :-(

Tony

EDIT:

It may be something simple like a dry joint on the DATA pin for this particular IC. The DATA pin transfers RAM data in and out of the device, it is pin #5. As mentioned, I don't know which IC has the problem, but you might consider checking for corrosion on the ROM IC's. If you are handy with a soldering iron, I would try re-soldering pin #5 on all the ROM ICs.

ID's for these 8 pin IC's are probably: 1818-0231, 1818-0232, 1818-0550 and 1818-0551.

Try not to touch the component connections on the board, the IC's can be damaged by static from your body.
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07-27-2022, 03:30 PM
Post: #3
RE: HP-67 not behaving?
Tony - thank you so much for recreating! It does indeed seem like part of the RAM has failed (for example where the display format is stored, and program steps?). I am experienced with the iron and static prevention, I’ll try not to mess up the rear label and crack this baby open to investigate! Due to travel this probably won’t be until later this week. I will report back!

Cheers

Mark
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07-27-2022, 04:31 PM (This post was last modified: 07-27-2022 04:31 PM by AndiGer.)
Post: #4
RE: HP-67 not behaving?
(07-27-2022 06:03 AM)markhen Wrote:  This machine was professionally restored about 10 years ago ...

(07-27-2022 03:30 PM)markhen Wrote:  I’ll try not to mess up the rear label ...

If wise maybe the restorer left out the screws underneath the label?!?
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07-27-2022, 05:18 PM
Post: #5
RE: HP-67 not behaving?
Good point!! I will remove the other screws first - thanks for idea! The restorer did an amazing job of keeping the label smooth (far better than my attempts on other machines).
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07-29-2022, 12:36 AM
Post: #6
RE: HP-67 not behaving?
Since there are so few (as far as I know) people who restore 67/97s who have large numbers of serviced units in their "resume", who restored yours?

After 10 years is this person in business?

Everyone knows Randy Sloyer, there was also a guy in Placerville CA, but both have stopping servicing due to health years ago.

thanks!
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07-29-2022, 04:38 AM
Post: #7
RE: HP-67 not behaving?
Duane - checked my records and my 67 (and 2 65s) were serviced excellently by Richard Anthony in Placerville, CA in early 2010 (>12 years ago now!!). I don't know if he's still servicing?

Regards -

Mark
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