HP 25

[Steve Hey]

Hi HP, ers,

I am new to the forum but have been using HP 25, 29C and all the 41's, great machine, use mainly for survey etc... on a regular basis.

I have HP 25 with problem of when in program mode most keys show 13 00, with f and g working fine, in run mode everything is also working fine i.e calculations are no problem.

Any assistance in solving my problem will be appreciated, I am not an expert in any way on pcb's.

Also wondering if Bernard of panamatik's repair of ACT is the way to go.

Cheers Steve

[teenix]

Sounds like a ROM issue rather than keyboard, so maybe the repair kit will fix it.

cheers

Tony

[Steve Hey]

Hi Teenix

Many thanks for your advice on possible ROM problem, are ROM parts avaliable anywhere.

I have the ACT repair kit coming for my 29C that got plugged in without a battery, so I may put that into the 25 as a trial.

Kind regards,

Steve

[ThomasF]

Hi Steve,

Could it be the RAM-chip that is failing?

All stack registers etc are locally in the ACT (the "cpu") but program memory and storage registers are in a separate RAM-chip.

Can you check that the storage register work? I.e. STO n (n:0..7) and RCL n works as expected.
If the RAM fails, normal calculation still works fine (since stack and internal registers are in the ACT) - but statistics (mean, sdev etc) will not since they make use of the r3-r7 registers.

Panamatik's ACT replacement will most probably help in that case, since the new ACT contains its own RAM and is not dependent of the old external RAM-chip.
And even if it would be the ROM (which I don't think), Panamatik's ACT will also work, since it also overrides the external ROM-chip.

Best regards,
Thomas

[Steve Hey]

Hi Thomas

Thanks for your reply

Will do the steps you recommended

I will let you know

Best regards

Steve

[Steve Hey]

Hi Thomas

Checked Sto 0 to 7 reading 13 00 sane for RCL nn

So I think I need ACT repair kit

Best regards

Steve

[ThomasF]

Hi Steve!

Sorry for being unclear - but I meant that you could check STO/RCL in RUN-mode.

In RUN-mode (normal calculation), can you store anything in the registers?
I.e. does "12345 STO 5 CLx RCL 5" result in "12345"?

Code:

Press        Display shows
12345        "12345"
STO 5        "12345.00"
CLx          "0.00"
RCL 5        "12345.00"

Or, if you press "g EEX" (clear reg) and then repeatedly on "Sum+" (the summation-key below "g")?
If RAM is correct, then the value in the display should increase with one for every time you press "Sum+" like this:

Code:

Press        Display shows
CLx          "0.00"
g EEX        "0.00"
Sum+         "1.00"
Sum+         "2.00"
Sum+         "3.00"

and so on ...

If this doesn't work, my 2 cents are that the RAM-chip is broken, and yes, a ACT replacement kit is probably needed (or a RAM-chip from another HP25 which might have another fault chip).

Cheers,
Thomas

[Steve Hey]

Hi Thomas

In the 12345 test 0.00 at end
In the g eex test result is 1.0

So I believe you are correct RAM chip corrupted

So AMT repair kit sounds like the solution

Kit is on its way from Bernhard, will let you know result

Best regards

Steve

[Amafan]

@Steve
I have the same problem. Please let us know how it works including the purchasing and shipment of the repair kit.

(09-28-2021 02:17 PM)Steve Hey Wrote:  Hi Thomas

In the 12345 test 0.00 at end
In the g eex test result is 1.0

So I believe you are correct RAM chip corrupted

So AMT repair kit sounds like the solution

Kit is on its way from Bernhard, will let you know result

Best regards

Steve