HP-70
Serial number 1431A06331, 1974, 31st week, USA
Accessories Battery pack, US wall charger
Condition Clearly used but still excellent. Silver lining worn near the on/off switch. All buttons and display segments are working. The "PMT" key as a bit of a contact problem.
Repairs, Comments
Acquired 5.11.2015
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HP codename, series unknown, Classic.
Type, Precision, Input mode Business, 13 BCD digits, exponent ±99, Reverse Polish Notation
Programmable No
Performance Index -
Memory 2 registers M and K, not permanent
Display 13 digit 7 segment red LED plus sign
Special features 2 memory locations M and K. K powers up with the value of 12.
Original Pricing, Production $275, 1974 - 1975
Batteries 3x AA battery pack equipped with 1.5V rechargeable or normal batteries.
Dimensions Length 15.1cm, Width 8cm, Height 3.6cm
Links HP-70 Owner's Handbook, PDF, 125 pages, English, July 1974
HP-70 Demonstration Book, PDF, 17 pages, English, unknown release date
Comment The HP-70 was a cheaper version of the more powerful HP-80. It had a very short life and was quickly replaced by the cheaper and more powerful HP-22. Only relatively few HP-70 units were sold and as a result they are rare, and nowadays difficult and expensive to get.

Explanation of financial function keys.
To reset all values to 0 press "CLR"
n
 Number of payment and interest periods
i
 Periodic interest rate in percent
PMT
Payment amount per period, may be negative or 0
PV
 Present amount at beginning of first period
FV
 Future amount, after n periods of payments and compound interest
Pressing "DSP" and one of the above keys shows the current value of the associated variable.
To enter a value for a variable, key in the number and press the associated button.
To calculate a value press the desired button without entering a number. Based on the numbers stored in the other four variables, the solution is calculated.
Example:
  • Press "CLR"
  • 5% interest rate: Press 5 and "i"
  • Start value of $1000: Press 1000 and "PV"
  • Final value of $5000: Press 5000 and "FV"
  • Press "n" to calculate the number of periods needed reach the final value: 32.99
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