[TenTec] unstable Omni D display fix-problem found

[Mike Bryce]

the counter-on-a-chip is a MK50398N

the multiplex chips are 75491APC and 75492apc

there's two 491's they are the segment multiplexer and the 492 is the  
display multiplexer

( I guess technically, the 50398 does the multiplexing, and the three  
other chips are used to decode and drive the LEDS)

both the 75491APC and 75492apc are not stocked anymore by ten tec.  
These chips are really hard to come by, but again, there's the part  
miners out there that have them listed, but with  $250 min to buy.

I did a quick look at NTE and they seem to have a replacement for the  
491, but have not looked deeper into the project.

there's three possibilities here with a dead Ten Tec Omni LED display

1. Get another junker for parts
2. Use a external freq counter
3. The dead one becomes the part donor

and...

there's a few places that sell "digital dials" that maybe used,but  
none that I have seen drive LEDs, they are usually for LCD displays.


Mike, WB8VGE
>
What are the chips?

73, Jerry, K0CQ