Archive for the ‘Hewlett-Packard’ Category

Hewlett-Packard HP-97 (Boxed) – Replacement Drive wheel & Battery

April 26th, 2015 No comments
Hewlett-Packard HP-97


The HP-67 was a magnetic card-programmable handheld calculator, introduced by Hewlett-Packard in 1976 at an MSRP of $450. A desktop version with built-in thermal printer was sold as the HP-97 at a price of $750.

Marketed as improved successors to the HP-65, the HP-67/97 were based on the technology of the “20-series” of calculators (HP-25, HP-19C etc.) introduced a year earlier. The two models are functionally equivalent, and programs on magnetic cards can be interchanged between them.


The 67/97 provide a complete set of scientific, statistical and engineering operations, including trigonometrical, logarithmic and exponential functions, coordinate conversions, average/deviation etc.

The HP-67/97 series featured a program memory of 224 eight-bit words. The two extra bits per word compared to the HP-65′s six allowed the designers to store any program instruction in a single memory cell (“fully merged keycodes”) even if it required multiple keystrokes to enter (see image). Programs could include 20 labels, subroutines (3 levels deep), four flag registers, 8 comparison functions, and extended index and loop control functions.

At 15 digits, the display was wider than those of the predecessor models, although the decimal point was displayed on its own digit position. The HP-67 keys carry up to four functions each, accessed through “f”, “g” and “h” prefix keys (gold, blue and black labels, respectively). The model 97 had more (and larger) keys, therefore only two functions were assigned to each key. When interchanging magnetic cards between the HP-67 and the HP-97, the calculators’ software took care of converting the key codes, and emulated the 97′s print functions through the 67′s display.

The HP-67 is powered by a pack of three AA-sized nickel-cadmium rechargeable batteries. Owing to the power requirements of the built-in thermal printer, the HP-97 employs a larger battery pack and more powerful charger.

Memory and programming:

Of the 26-register data memory, the first ten (“primary registers”) could be accessed directly, ten more as an alternate register set, and the remaining six had special functions for statistical operations and as an index register. Using the latter, a program could access all 26 registers as a single indexed array. Data memory is not permanent as in later models, i.e. register contents and program are lost when powering off.

The built-in magnetic card reader/writer could be used to save programs and data, with the ability to combine data from multiple cards. The same magnetic card format was later used for the HP-41C which offered compatibility to the 67/97 through software in the card reader. HP offered a library of programs supplied on packs of pre-recorded magnetic cards for many applications including surveying, medicine, as well as civil and electrical engineering.

In addition to software and support from HP, an active user community supported the HP67/97 as well as the other HP programmables of the era. The group was called PPC and produced the PPC Journal. One of the notable contributions of the group was the development of a “Blackbox” that allowed pseudo-alphanumeric displays.

Gallery (Before cleaning):

Gallery (Replacement Drive wheel & Battery):

Gallery (Under the Cover):



HP-85: Pinch Roller reconstruction / Cleaning Rubber / DC-1000 Fix

March 23rd, 2013 No comments

I had several problems with the repair of the Hewlett-Packard HP-85.

The first problem was the way to reconstruct the pinch roller using a latex tube, this is a very bad choice, then i have used a 10mm heat shrink, this choice instead is very good.

The second problem was the rubber parts of the pinch roller are literally dissolved and the rubber is went to cover the optical diode and part of the pcb and of course nothing has worked and the tape drive was always in stalled state.

After cleaning, the drive started to work perfectly. The last problem are the magnetic tapes 3M DC-1000 instead of HP DC-100, for the correct operation you must perform a modification by adding a resistor of 2kohm in parallel to the already present on the pcb. After this mod you need to format the tape with the “erasetape” command.

I must also thank John of the site for the support.



Hewlett-Packard Model 85 (HP-85)

March 23rd, 2013 No comments
Hewlett-Packard Model 85 (HP-85)


from Wikipedia:

The Hewlett-Packard series 80 of small scientific desktop computers was introduced in 1980, beginning with the popular HP-85 targeted at engineering and control applications. They provided the capability of the HP 9800 series desktop computers in a smaller package including storage and printer, at half the price. Ultimately, the market for desktop computing would go to IBM PC compatible personal computers (the IBM PC was announced shortly after the 80 series).

The first model of the Series 80 was the HP-85, introduced in January 1980. In a typewriter-style desktop case, it contained the CPU and keyboard, 16 kB dynamic RAM, a 5-inch CRT screen (16 lines of 32 characters, or 256×192 pixels), a tape drive for DC-100 cartridges (210 kB capacity, 650 B/s transfer) and a thermal printer. Both the screen and printer display graphics in addition to text, and the printer can copy anything shown on the screen. The chassis includes four module slots in the back for expansion which can hold memory modules, ROM extensions, or interfaces such as RS-232 and GPIB.

All components were designed at the Hewlett-Packard Personal Computer Division in Corvallis, Oregon, including the processor and core chipset. Later models offered variations such as different or external displays, built-in interfaces or a rack-mountable enclosure.

The machines were built around an HP-proprietary CPU code-named “Capricorn” running at 625 kHz (0.6 MHz, sic) and had a BASIC interpreter in ROM (32 kB). Programs could be stored on DC-100 cartridge tapes or on external disk/tape units.

Despite the comparatively low processor clock frequency, the machines were quite advanced compared to other desktop computers of the time, in particular regarding software features relevant to technical and scientific use. The standard number representation was a floating point format with a 12-digit (decimal) mantissa and exponents up to ±499. The interpreter supported a full set of scientific functions (trigonometric functions, logarithm etc.) at this accuracy. The language supported two-dimensional arrays, and a ROM extension made high-level functions such as matrix multiplication and inversion available.

For the larger HP-86 and HP-87 series, HP also offered a plug-in CP/M processor card with a separate Zilog Z-80 processor.


source: wikipedia