I tend to agree with
@nomadradio , many a PLL still "sinks" current into itself (read this as looks for Pins to be set high) so to solve for wiring and Polling of display issues, they use common POSITIVE (Anode) source with dropping across the Segments and the BCD or "Encoder" together - one feed, branches to the segments and to the encoder - uses a separated "pole" for feed to keep display and Channel selector separate and noise free interactions from each other.
Since they've gone to LCD, the "noise" problem is handled differently - LED though, is all thru that channel display board and it's set of noise filtering.
The older 787 used an LCD channel display and encoder - but still used single supply feed.
So some displays, LED style...
Uniden PC-68LTX
Others LCD...
Uniden 787
Why would this be important?
The Channel SELECTOR in the 68LTX is BCD and LED integrated like their older predecessors and uses a multiple Pole Wafer switch, hence the support for the channel display is on the selector and Channel board for the front panel
- - in radios like the 787, A LOT of support was done at the front panel for it's display, channel and PLL interface and uses Analog switches to be buffered with Digital Darlington on the main PCB - reducing the noise.
- This is always reciprocal - they had to use an oscillator to "poll" for changes in switch status. So in doing that, actually injected noise from itself in the polling of the display - so they have other issues to tame (still to this day some "buzz" can be heard as a high-pitched "ring" or whine from this front panel shielding problem.)
So your missing segment, with LED displays having been improved considerably since the original days - may also indicate a "Face-plant" radio - radio that suffered from getting dropped and it landed on its front panel with the Channel knob taking most of the impact - that may mean internal damages can show up later.
