The Museum of HP Calculators

HP Forum Archive 18

[ Return to Index | Top of Index ]

HP-25 fails to store programming steps
Message #1 Posted by Alberto Fenini on 26 Jan 2009, 4:40 p.m.

Dear All,

first of all congratulations for the forum, it is very well done and very complete.

I've been browsing for a while, waiting for my recently ebay purchased HP-25 (S/N 1512A28495) which is arrived today.

I have to admit it, one thing is browsing for pics, articles or memos about this amazing machine but having a real one in your own hands it's all another story.

Forgive me for my english, I'll do my best but I can't promise miracles, it won't get much better than this in the short time.

Anyway, the machine is in very good conditions, the original batteries have been replaced with AA Alkaline, and the basic maths are performed ok.

However I can't manage to use registers. No matter what numbers I store in a register, the RCL key only brings back a zero value.

The programming issue is quite similar, the HP-25 enters in the programming mode, but no matter what keys are pressed, no key codes are stored, and as a result of this no program can be executed.

All I get is a line like : XX 13 00 where XX gets incremented for any key pressed.

Just to be sure I was doing things properly, I have used the great HP-25 Java simulator and no need to say, it worked out.

Does anyone has ever experienced anytinhg like this ?

Thank you very much for reading, and thanks in advance for any hint !!

Greetings to everyone from Italy

      
Re: HP-25 fails to store programming steps
Message #2 Posted by Walter B on 26 Jan 2009, 4:52 p.m.,
in response to message #1 by Alberto Fenini

Buona sera, Alberto,

benvenuto al foro! Scusi, but these were the last good words, since I fear your HP25 may be partially defective. I remember having read of similar symptoms here some time ago. Perhaps one of the guys who was immediately affected will respond. Sorry, but enjoy what is working still.

Edited: 26 Jan 2009, 4:53 p.m.

      
Re: HP-25 fails to store programming steps
Message #3 Posted by Randy on 26 Jan 2009, 5:24 p.m.,
in response to message #1 by Alberto Fenini

The unit has a defective RAM Integrated Circuit, HP part number 1818-0154. The only source will be from another HP25 :(

            
Re: HP-25 fails to store programming steps
Message #4 Posted by Alberto Fenini on 26 Jan 2009, 7:18 p.m.,
in response to message #3 by Randy

Hi there, thank you very much for your replies.

Well, it's not good news to hear, but I wasn't going to programme it anyway.

I have actually purchased it because I was using a similar machine back in the school days (that was an HP-25C) and I really love it.

The idea was to use it now for everyday maths, and since this is something this little cutie still does, I'm overall happy about it.

There is actually a bouncing problem with keys 1 and 4, and the key 5 it's a little bit tricky. I have read in the forum that disassembly the keyboard and cleaning the contacts is a higly risky task, do you know any simpler way to get the keys working properly ?

Again, thank you very much for support, it really makes me feel back in the 80's.

                  
Re: HP-25 fails to store programming steps
Message #5 Posted by Jon S Canale on 27 Jan 2009, 5:25 p.m.,
in response to message #4 by Alberto Fenini

Don't give up yet! May not be a bad chip - not just yet. Search this board a little further, and you might find a description of this problem. There are some brilliant people here who found some fixes.

My 25c acted like yours since 1981 or so. But I couldn't throw it out. Just recently, I found a message or article here that suggested that the problem with the chip was that it just had to "warm up"! It actually did act that way! There's also the possibility that there is a bad ground on the chip which might be solvable.

So do some more searching here - just found one of the articles: A Common Woodstock Problem and Repair Suggestions Posted by "katie" on 16 Apr 2002, 10:14 p.m. I think she is still lurking on this board. There's another article around here mentioning the noisy clock signal.

                        
Re: HP-25 fails to store programming steps
Message #6 Posted by Katie Wasserman on 27 Jan 2009, 9:20 p.m.,
in response to message #5 by Jon S Canale

I'm still here! I try not to lurk, I just haven't had much to say lately that someone hasn't already said on this fine forum.

Alberto, feel free to email me if I can help you fix your 25. What I wrote about does take a little bit of soldering iron work but not too much. It might be worth a try even if you don't find that the memory starts working after a warm up period.

      
Re: HP-25 fails to store programming steps
Message #7 Posted by David Hayden on 27 Jan 2009, 5:21 p.m.,
in response to message #1 by Alberto Fenini

What a great machine that HP 25 was/is. I had an HP 29C in high school and a really loved it. Made the mistake of loaning it to a girlfriend after college and I haven't seen it since :(.

The thing I liked so much about those machines (Woodstocks?) was the form factor. Hold it in your palm, them move it out so your holding it with your 4 fingers. Now your thumb can reach all of the keys. I remember many nights of homework with a pencil in one hand and the 29C in the other, clicking away with my thumb to get my answers. It worked great.

I haven't seen a calculator since that was so easy to operate one-handed.

            
Re: HP-25 fails to store programming steps
Message #8 Posted by Jon S Canale on 27 Jan 2009, 5:28 p.m.,
in response to message #7 by David Hayden

Quote:
I haven't seen a calculator since that was so easy to operate one-handed.

I second that! The 11c which I got to replace my "defective" 25c, was never as handy. However, at 29 years old, that 11c is still running and I use it just about every day!

                  
Re: HP-25 fails to store programming steps
Message #9 Posted by Mike Morrow on 27 Jan 2009, 6:26 p.m.,
in response to message #8 by Jon S Canale

I would have liked to see all the features of the HP-34C built in to an HP-29C Woodstock form factor. They both have the same number, types, and arrangements of keys/switches, and the same number of LED segments. The HP-34 is a significant technical advance over the HP-29, yet the 34's construction feels weak and flimsy, with poor battery compartment design. One can't make those criticisms of the Woodstocks!

This would create the untimate "Ueber-LED-Calculator"!

                        
Re: HP-25 fails to store programming steps
Message #10 Posted by Walter B on 27 Jan 2009, 6:49 p.m.,
in response to message #9 by Mike Morrow

Quote:
This would create the untimate "Ueber-LED-Calculator"!
... genuine with umlaut only: "Über-LED-Calculator" d;-)

Seriously, what I missed most in my 25C was L.R.

                        
Re: HP-25 fails to store programming steps
Message #11 Posted by Randy on 27 Jan 2009, 7:48 p.m.,
in response to message #9 by Mike Morrow

Quote:
One can't make those criticisms of the Woodstocks!

So you actually prefer the behavior where they self-destruct when the battery is bad or missing and the charger is connected?

Or is it when the keyboard has intermittent keys due to battery out-gassing and leakage?

While I will not disagree the 30 series was far worse, the 20 series had more than its own share of fatal flaws.... IMHO :)


[ Return to Index | Top of Index ]

Go back to the main exhibit hall