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HP Forum Archive 06

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repair of 15C?
Message #1 Posted by Dan Kalish on 27 May 2001, 3:28 a.m.

I've had this 15C since it was brand new (about 1985) and now its on the fritz.

The problems started about 2 days ago, it intermittently responded to key strokes. Then the screen just went blank and now it doesn't respond at all.

I've tried replacing the batteries without success. (I WILL try another set of new batteries.)

Any ideas on where to get it repaired? I'm in NYC.

Is it worth anything to collectors as it is?

I love this calculator; for some features, its easier to use than the 48G I have.

I've checked eBay and they're going for about $155., usually in unknown condition. So it sounds like a repair might be less.

Suggestions would be appreciated.

Thanks in advance.

Dan Kalish kaliushkin@att.net

      
Re: repair of 15C?
Message #2 Posted by thibaut.be on 27 May 2001, 4:24 a.m.,
in response to message #1 by Dan Kalish

Try to short-circuit the battery contacts and then re-install the batteries. If it won't start, try with ON/- to reinitialize the calculator. Are you sure of your batteries ?

            
Re: repair of 15C?
Message #3 Posted by Dan Kalish on 27 May 2001, 7:35 p.m.,
in response to message #2 by thibaut.be

Thanks, but still no go.

The batteries were 4.0V without load; I replaced two of them so its now 4.3V without load. Still doesn't work. As I said, I will get another set of batteries.

Tried short circuiting. Nope. Tried On\-. Nope. The screen remains blank.

BTW, this is the version with a screw in the upper left hand corner, next to the batteries. s/n 2514A04152.

Any more ideas?

Dan Kalish

                  
Re: repair of 15C?
Message #4 Posted by Thibaut.be on 28 May 2001, 2:31 a.m.,
in response to message #3 by Dan Kalish

Is there any corrosion on the contacts ? Try to clean them. If you feel skilled enough, remove all screws and try to see ifpower supply leads are not too corroded. Make a good short-circuit, even invert the polarity for a short moment, then reinstall the batteries and give it another try....

                        
Re: repair of 15C?
Message #5 Posted by David Smith on 28 May 2001, 6:34 p.m.,
in response to message #4 by Thibaut.be

If you have opened up the unit, short out all the electrolytic capacitors. This is a sure way to get the continuous memory so forget. It has brought several balky 41C's back to life.

                              
Re: repair of 15C?
Message #6 Posted by Dan Kalish on 29 May 2001, 1:54 p.m.,
in response to message #5 by David Smith

Thanks for these tips.

First question: do the batteries sound alright? Two are new; one is an old one. Second question: whether the contacts are broken off. (I wish I could find my 10C to compare them.) The cathode (-) lead is shaped like an anvil: like the top of a T. The anode (+) lead is a spring.

I have a DMM: should I be able to test anything between the leads?

As to opening it up, fortunately this model has one screw in the rear upper left hand corner. Apparently, later models didn't. Do I remove that screw and then wedge the calculator open?

I don't know anything about the way these calculators work but it *feels* like the button controller, if there is any such thing, has gone bad.

Dan


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