HP 67: charging of battery pack

[PANAMATIK]

(04-22-2017 04:04 PM)Den Belillo (Martinez Ca.) Wrote:  The 67 is susceptible to this problem. I don't even trust clean contacts. Contacts are usually the problem; batteries have to be pretty bad off to cause this. There are several anti-corrosion, conductive grease products on the market. Every manufacturer of aluminum wire & cable has one as do most breaker suppliers. No Lox brand can be bought in about a one ounce tube here in the states. As they said about Brylcreem; a little dab'll do ya.

Or you could just charge your battery in your 35, 45, 70, or 80. They're impervious to this by design.

I have to disagree. The HP-67 is not susceptible to this problem. When calling it a "Woodstock" calculator, this belongs only to the chip set but not to the charger. This will become clear when you have a look to the charger slot. Like the "Classic" calculators, it has three contacts. If you insert the charger plug pins 1 and 3 will be interrupted and the battery plus will become completely disconnected from the circuit, the high charging voltage is applied only to the battery, thus it is irrelevant to have a battery pack inside while charging and working with it while charging.

Because the HP-67 was a more expensive model, the charger was designed more costly to deliver two voltages, one regulated voltage for the circuit and one unregulated for charging. Only the cheaper "Woodstocks" used a charger with only two contacts and only one voltage for working and charging, this design requires the batteries inserted while charging and having switched on the calculator.

The HP-67 is save to charge and work without batteries like the HP-35,45,55,65,70,80.

Bernhard