Hardware questions of HP-67

[Paul Berger (Canada)]

(09-29-2015 01:33 PM)Waon Shinyoe Wrote:  Just acquired a heavily corroded HP-67. After some cleaning work with vinegar and alcohol, I have the following questions:

1. What's the use of those shiny metal contacts? (Please see the attachment)

2. The keys B, GTO, g, and ENTER don't work. They are on the same column, so I doubt what can cause such problem and how to repair it.

3. Since the battery terminals are all gone, I soldered wires and installed a battery box. However, if I use batteries instead of AC power supply, the power on LED would blink once, but there is no display. I check the wires and I'm sure they are connected to the contact points of the AC power port. (BTW my multi meter was broken these days I will update the post once I acquire a good one. )

4. When I use AC power, I have to press the ON/OFF switch hard to keep it on. I thought it might be a problem of assembly, but I didn't find anything wrong.

Also, is there anything like a service manual? Thanks a lot.

1. Those are the switches for the card reader small nylon balls above them push them down to contact pads on the circuit board as the card passes through the reader.

2. The key are scanned in a row/column matrix so if all the keys in one column do not work there is either a break in the circuit or else there is a problem with the ACT chip, however there will be a lot more than 4 keys in a column so I would expect it is a break, the minus, plus, multiply, and divide keys are on the same column.

3. The AC supply for the 67 like all classics provides 2 voltages one is +5V to power the calculator and the other is the charging voltage. Where the power cord plugs in there is a metal blade that should short two of the 3 pins when the connector is removed, if that is not connecting it will not work from batteries.

4. That sounds like the contacts are degraded or are bent so that they do not contact the board properly.

I do not know of a service manual however the circuitry is very similar to the 97 minus the PIK chip in the 67 the keyboard columns are driven directly by the ACT.