On Friday, 30 June 2017 12:29:30 UTC+1, John-Del wrote:
On Friday, June 30, 2017 at 2:51:21 AM UTC-4, tabby wrote:
On Thursday, 29 June 2017 22:03:35 UTC+1, wrote:

Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

Yes from neon channel selector sets, touch selectors & older pushbutton bar tuning sets. Show us the circuit.


NT

Hmmm... you're drudging up long forgotten memories. Back in the late 70s Zenith used a varactor tuned electronic tuner that used neons as indicators for the pre-set push button selector, and sometimes those neons were the cause of the TV jumping channels or refusing to engage a selected channel.

By 1984 I would think that all manufacturers would be using a true digital selector system for anything no using a mechanical tuner.

Unfortunately, OP didn't say if the TV would scan downward to channel 2 or jump to it. He also didn't say if the TV normally defaulted to channel 2 when the TV was powered off or when the AC was lost.

There were a lot of TVs then that used a digital keypad, but were not remote control and used a mechanical AC switch and volume control. In this case, it's possible that the uPc is only used for channel functions and his problem could be on the micro's reset line.

Until the OP tells us what the technology is we have really no way to advise usefully. 1984 could be a few things, switched linear pots with varicap is likely, or touch sensors maybe. There were also old technologies used in some sets, so can't completely rule out a mechanical selector device operating a tuning bar.


NT