Re: HP41 card reader weirdness Message #7 Posted by plasmoid on 28 Jan 2007, 5:12 p.m., in response to message #1 by Les Wright
Hello Les,
Concerning your recent difficulties getting your HP-82104A card reader to work properly with your HP-41CV:
I would like to assure you that your rebuilt HP-82104A card reader will function equally well with HP-41C, HP-41CV or HP-41CX.
While on rare occasion it may happen that a given magnetic card is defective and will not properly record, when reading a properly recorded card, there should be virtually zero error rate, typically less than 1 error in 1000 passes. Unless you've gotten something sticky on your cards, your should not have trouble reading them.
Continuing errors indicate a problem with your calculator, batteries, or battery charger.
CAUTION: A defective calculator can scramble the programming on even a "write protected" program card. If when reading a card, the card stops suddenly and the HP-41 displays anything other than "LOW BAT", this is usually an indication of problems with the electrical contacts in your calculator. The calculator may display "MEMORY LOST", or a scrambled display, or the calculator may simply turn off. Furthermore, while a "LOW BAT" warning may be a true indication of weak batteries, it may also be the result of deteriorated battery contacts.
It is a common misconception that the HP-82104A causes a heavy drain on batteries. A properly rebuilt and adjusted card reader draws only a moderate current. In testing my rebuilt card readers, I will write approximately 180 cards and read them back 1800 times before having to replace the alkaline batteries in my test calcluator. For most users, this is less than a year's use, and for the overall health of your cacluator, batteries should be replaced every year.
Although it is possible for contaminants to foul the port contacts of an HP-41, this is usually not the cause of problems. The 'wiping' action of module/accessory contacts as they are installed tends to push dirt and other loose contaminants out of the way.
The most common problem with HP-41 calculators is deterioration of the gold plating on internal and external electrical contacts. The gold plating on the contacts can be lost through wear or corrosion, and once the copper substrate of the contacts has been exposed, it will oxidize to a non-conductive state.
The gold plating is meant to prevent oxidation of the copper substrate, but extended exposure to battery leakage will eventually exploit microscopic imperfections and undermine the gold. The gold plating on the battery contacts and the port contacts can also be worn away by heavy use.
Simply cleaning and/or polishing the contacts is only a temporary fix, as the exposed copper will again oxidize to a non-conductive state in a relatively short time. The gold plating must be properly restored. Note that for electrical contact purposes, gold cannot be plated directly over copper, as copper ions will migrate into the gold layer during the plating process, contaminating the surface.
As a final related note, and for the sake of completeness: Cracked plastic around the four screws that hold the two halves of the calculator together can also result in malfunctions similar to those caused by deteriorated electrical contacts. These are the screws located under the rubber feet, and they must hold the calculator together firmly at all four corners to insure the integrity of the internal connections.
If you send me your HP-41CV, I can restore the plating on the contacts.
Regards,
-plasmoid
Edited: 28 Jan 2007, 7:00 p.m.
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