I have the above clock. (it lights up more or less orange (Struggling to stay on topic..))
It's the grandfathers clock version, that uses filament bulbs for the digit segments.
After all these years, it has finally failed. It sits, displaying 12:00, and refuses to do anything else. Normally, if there had been a power failure, it would display a blinking 12:00. There is no blink.
I can not identify the 40 pin IC. No markings. If I look up the schematic, it shows they used one of two ICs, depending on which manual I use. The Heathkit part numbers are 443-702 or 443-848. The 443-848 seems to cross to a MM5316, the other, 443-702, MAY cross over to a F3817PC. I can find a datasheet for the MM5316, but not the F3817PC.
I guess what I need to know is if they are interchangeable....I can locate the MM5316, but the F3817PC seems to be made of unobtainium... The MM5316 actually crosses to an NTE number.
Any thoughts or inspirational advice appreciated...
Kerry