HP Calculators By Model Type

Classic
Voyager
Woodstock
Spice
Pioneer
Champion/Clamshell
Coconut
Charlemagne

Classic

Example
Calculators HP-35, HP-45, HP-55, HP-65, HP-67, HP-70, HP-80
Display 13 digit 7 segment red LED plus sign
Keys 35
Dimensions Length 15.1cm, Width 8cm, Height 3.6cm
Special Some models equipped with a magnetic card reader
Shortcomings It is hard to make a power supply from a a regular off-the-shelf converter
Batteries
  • 3x AA battery pack equipped with 1.5V rechargeable or normal batteries.
  • It is possible to cut open the pack in various ways to be able to insert new rechargeables or to insert regular AA batteries.
External supply
  • Special AC power supply with three contacts and two separate feeds for battery charging and calculator.
  • Part numbers: 00035-60008, 03502A, 82001A/B, 82002A/B/C, 82010A (120/240 VAC), 82022A(240 VAC), 82011A (240 VAC)
  • Charger output: 3.6-4.7V DC 200mA for the calulator, 4.2V DC 60mA for the battery charger (approximate values).
  • The two outer contacts (see picture below) are the plus poles and feed the calculator and the rechargeable batteries. The center contact is ground. When the charger plug is inserted a spring is dislocated which usually connects the two outer contacts so that the batteries feed the calculator. 
  • Note: Do only connect the power supply if you have rechargeable batteries installed!
  • Note: Some models will only work properly with the power supply if a battery pack is installed (ie. HP-65). In this case rechargeable batteries MUST be used!!
How to open
6 screws are to be removed as shown in the picture below. 
  • Use a sharp cutter knife to pry out the plastic covers of the top two screws.
  • Use the same cutter knife to cut underneath the top ears of the back label. Then bend up the ears to get to the screw holes. Alternatively, using the cutter knife you can cut two round holes into the back label to get to the screws. This will undoubtedly ruin the back label - but bending up the ears will ruin it as well...
  • To get to the lower two screws DO NOT rip out the plastic feet! Rather, lift them gently on the outer side without removing them entirely.
  • Once those 6 screws have been removed the back can easily be taken off.

Voyager

Example
Calculators HP-10C, HP-11C, HP-12C, HP-15C, HP-16C
Display 10 digit 7 segment black&white LCD display plus sign
Keys 39
Dimensions Length 7.9cm, Width 12.9cm, Height 1.5cm
Special Also named "Series 10"
Shortcomings Dust tends to settle behind the display. This is hard to remove because the plastic stakes that hold the printed circuit board must be cut off in order to remove it. 
Batteries
3x small button sized cells, 1.5V each. 
Newer models of the HP-12C require only one large button sized cell, 3V.
External Supply None
How to open
  • Do not remove the HP logo! There's nothing underneath it.
  • Underneath the 4 rubber feet on the backside of the unit are four screws to be removed. The back cover then comes off easily. Don't loose the two little springs that stick out thru holes in the circuit board!
  • Towards the bottom of the unit is some transparent film that needs to be removed.
  • Newer models only have one single circuit board that is held by numerous black plastik stakes that have the top flattened. Use a sharp cutter knife to cut off all the tops. Now the circuit board can be removed and it is easy to get to the keys and the display for cleaning. WARNING: It is usually not possible to fix the stakes lateron!!
  • When the unit is reassembled don't forget the little springs.
  • Also, remove the spring in the battery compartment before reinstalling the circuit board. Insert the spring once the board is in place.
  • Since the stakes are now gone the circuit board must be supported from the back. I used a few pieces of packaging foam; the back panel presses the foam towards the circuit board and holds it firmly in place. Small disadvantage: When you look at the calculator from the side you will notice that the back panel got a little curved.

Woodstock

Example
Calculators HP-21, HP-22, HP-25, HP-25C, HP-27, HP-29C
Display 11 digit 7 segment red LED plus sign
Keys 30
Dimensions Length 12.7cm, Width 6.5cm, Height 2.9cm
Special -
Shortcomings The battery contacts tend to break off
Batteries
  • Battery pack with 2x AA 1.5V cells, regular or rechargeable.
  • It is possible to cut open the pack in various ways to be able to insert new rechargeables or to insert regular AA batteries.
External supply
  • Chargers: HP 82024A (120/230VAC) HP 82026A, HP 82041A/B/C
  • Output 10V AC (!), 180mA
  • Important: If the original HP power supply is used a rechargeable battery pack must be installed.
  • The special connector of an HP power supply can be cut off and connected to an off-the-shelf DC 4.5V power supply. In this case do not install any batteries! I'm not sure whether those 4.5V are sufficient to load a rechargeable battery pack.
How to open
Remove top two rubber feet and screws beneath them. Then gently push the power supply connectors (not the battery connectors!) so that the inner plastic part comes out at the front.
WARNING: While removing the back of the unit look inside the battery compartment at the battery contacts and make sure you don't break them off!

Spice

Example
Calculators HP-31E, HP-32E, HP-33E, HP-33C, HP-34C, HP-37E, HP-38E, HP-38C.
Display 10 digit 7 segment red LED plus sign
Keys 30
Dimensions Length 14.1cm, Width 7.5cm, Height 2.9cm
Special Also named "Series 30" or "Series E"
Shortcomings The cupper corners of the red display cover tend to break off when the unit is dropped. The battery contacts break off and the power supply has notorious contact problems.
Batteries
  • Battery pack with 2x AA sized cells 1.5V
  • It is possible to cut open the pack in various ways to be able to insert new rechargeables or to insert regular AA batteries.
  • Battery: HP 82109A
Warning: 
  • Do NOT connect the power supply if you have non-rechargeable batteries installed!
  • Some models will only work properly with the power supply if a battery pack is installed. In this case rechargeable batteries MUST be used!!

    • It is possible tob feed a Spice unit from an off-the-shelf power supply unsing 4.5V. Make sure minus is connected to the upper power supply contact latch (when look down to the unit from the front).
External supply
  • Charger: HP 82087A/B (HP 82089B, 82090A/B 220-240 VAC only). Do not use A models on continuous memory calculators
  • Output: 10V AC (!) , 180 mA.
  • Important: If the original HP power supply is used a rechargeable battery pack must be installed.
  • The special connector of an HP power supply can be cut off and connected to an off-the-shelf DC 4.5V power supply. In this case do not install any batteries! I'm not sure whether those 4.5V are sufficient to load a rechargeable battery pack.
How to open
  • Remove the top two screws.
  • Then lift the back cover at the battery compartment side.
  • Use **LOTS** of force to break the back cover loose from the lower end. This is a frightening procedure but the plastic cover doesn't actually get damaged - at least it stayed intact when I did this a few times.
  • Replacing it is much easier.

Pioneer

Example
Calculators HP-10B, HP-10BII, HP-14B, HP-17B, HP-17BII, HP-20S, HP-21S, HP-22S, HP-27S, HP-32S, HP-32SII, HP-42S
Display 12 digit 7-segment LCD
12 digit 5x7 LCD dot matrix for alphanumeric display
132x16 LCD dot matrix, 22x2 characters
Keys 35
Dimensions Length 14.7cm, Width 7.8cm, Height 1.5cm
Special Different kinds of displays. Some units equipped with infrared printer port.
Shortcomings Dust settles behind the display and cannot be removed
Batteries
b 3x small button sized cells, 1.5V each.
External supply None
How to open Never tried that!

Champion/Clamshell

Example
Calculators HP-18C, HP-19B, HP-19BII, HP-28C, HP-28S
Display 138x32 pixel black&white LCD, 23x4 characters
Keys 35 on the left, 37 on the right
Dimensions Length 15.9cm, Width 9.4cm (closed), 18.9cm (open) Height 1.8cm (closed)
Special Folding design. Some units equipped with infrared printer port.
Shortcomings The plastic housing next to the battery compartment lid tends to break.
Batteries 3xN (see Coconut)
External supply None
How to open Never tried that!

Coconut

Example
Calculators HP-41C, HP-41CV, HP-41CX.
Display 12 digit 14 segment black&white LCD for alphanumeric display
Keys 35
Dimensions Length 14.3cm, Width 7.8cm, Height 3.1cm
Special 4 extension ports, key overlays
Shortcomings -
Batteries
4x type "N", 1.5V each. Unfortunately, these are quite expensive.
The picture shows a HP-41 battery pack with two cells removed.
External supply Requires a special rechargeable battery pack with a connector on the side.
How to open -

Charlemagne