LED display available

[PANAMATIK]

Sometimes the LED display of Woodstock calculators don't show one or two digits, or one segment of all digits is missing complete. In most cases this can be easily repaired, because its only a loose contact of the common cathode of this digit or of the missing segment line. But if only a single segment of one digit doesn't show up, it cannot be repaired, because it is a contact problem of the very tiny microscopic bonded wires within the bubble display.

I made also acquaintance with completely corroded displays where any hope must be given up.

For these unrepairable displays I made a small layout last week, which replaces the complete display.

new display old display

I choose the QDSP6064 bubble display, which is available at SparkFun. It is also used by Chris Chungs wonderful NP-25 board.



The printed circuit board is compatible with the old display and can be replaced just by sticking it at its place.



The digits are slightly smaller than the original. Some of my HP-25s are brighter, others have the same brightness. And that's how it looks like.



Unfortunately the prototype boards I received today are not usable, because I made a mistake and placed the display off center by 2 mm, which doesn't look very good. I made a solder version which could be placed correctly for making the image above. If anybody has interest in this new replacement, and there is some demand, I will try to make a new batch, which I hope will fit perfectly then.

Of course, this was more easy than developing the new ACT

Bernhard