HP 59309A Digital Clock Repair

[morrone]

I picked up an HP 59309A that wasn't displaying the time correctly.  Turning it on, it looked to me like the display was changing every second, and the digit transitions happen at the correct time.  However, all of the digits were displaying the wrong pattern on the seven segment leds, and all with the same incorrect pattern for the same number.

I verified that the time logic is all working correctly internally through the HPIB port using a GPIBUSB.

I took the BCD-to-seven segment IC out of the display board and checked it on a bread board.  Nope, that it working correctly.  Then I checked the hex inverter IC that feeds the four BCD lines to the BCD converter IC.  Bingo!  Two of the inverters in the IC are bad.

So now I have the display fixed.  Yay!

I also cleaned off the stickers.

The top of the metal front piece was corroded, with these lifted bubbles of corrosion.  I descided to sand that down.  The texture doesn't match the sides, but nice clean sanded metal is a vast improvement.

There is only one problem remaining: it is missing the piece of plastic that overlays the LED display section.  Perhaps it was glass...I don't know.  See this image on hpmuseum.net:



Can anyone recommend a material to use to replace it?  It would be wonderful to recreate the lettering, but I would also be fine with just finding a piece of plastic that is a reasonable color that I can cut to size.

[miguelvp]

Found some images that might help:




some other images here:
http://www.leapsecond.com/museum/hp59309a/