line

An HP-32E repaired. Calculator 2

line

I bought this calculator from a well known auction site. It was sold as broken, for spare parts. perhaps a good candidate for a donor display to fix my other HP-32E. The calculator is in a optical good condition and all keys felt firm.

The battery lips were broken but the battery compartment was clean. The flex connector from the battery contact assembly to the power supply had some traces of blue colored cupper hydroxide that has etched away parts of the wiring of the flex connector. All three tracks were interrupted.

The pictures above show the internal of the HP-32E calculator. The left picture shows the key actuator sheet of the keyboard. The black plastic cradle on the right is holding the integrated circuits. These two parts are clamped together by two metal strips. The LED display is a separate module, clipped between the two boards.

I removed the metal clips to have a look inside.

HP32E_4

The opposite side of the keyboard assembly contains a flexible PCB, see the picture on the left. The picture on the right shows the three chips with bended leads and a small soldered PCB on top, containing a switch mode power supply. The flex wire connects the PCB of the left picture with the power supply and the battery contact assembly. On top of left picture the connector for the LED display leads can be observed.

The three chips are not soldered. They are pressed against the flex PCB. This construction technique was patented by HP in April 1978. See patent 4197586. This patent shows nicely the way this series is build.

HP32E_5

These pictures show the power supply PCB from both sides together with the flex connector. The left picture shows clearly the broken battery lips.

Display

Display backside

The picture above shows the LED display, which is stick between the flex PCB and the cradle. The models of the Woodstock series used this LED display, part nr. 1990-0657.

The optical state of this calculator is really good and worthwhile trying to fix it, instead of using it for spare parts. I repaired the broken flex by soldering thin cupper wires over the etched gaps. By scraping the flex with a sharp knife, the protection layer can be removed and the copper could be soldered without melting the flex!

New solder lips were assembled from pieces of copper foil and soldered on the small PCB.

After reassembling the calculator was fully functional again.

 

Radix selection

The selection for a dot or a comma for the radix is established by a jumper on the power supply PCB. The presence of the jumper selects for a dot as radix and a comma as thousand separator. The absence of the jumper selects the european convention, a comma as radix and a dot as thousand separator.

This calculator has the jumper opened (European version). See picture below.

Radix jumper

line

Spice repair related links:

line