I remember having someone taking apart a Cobra 2000, chassis and all, to repair the Frequency Display.
Once repaired, some other strange problems appear, drifting frequency, lights on display staying on - things like that. Found that letting the Frequency counter "Dangle" by it's harness - make it steady and work just fine.
Its' when it got put all back together - the same erratic problems re-appeared.
Well, it came also from a "smoker" that had not had any work done to the radio since they owned it.
The problem is -
The Chassis, once disassembled - your reassembly needs to be "perfectly" clean so the chassis itself doesn't generate a ground loop and noise pickup.
IT will receive just fine, Transmit too, but you'll have weird events like the clock refusing to keep time, the SSB mode - Frequency Counter won't stay steady.
These "support functions" are secondary to the main PCB, which isn't the problem, the board being one SINGLE piece - works just fine, the additional accessories are the errant stuff.
And so are the Accessories at fault, no - just the INTERCONNECTIONS are...
Hey, think of it...a radio or car or anything bolted together - once together - works as a unit because all the parts are equally connected at the same time at the same place with the same levels of corrosion if any or purity of materials for fresh metal to metal connection.
So as a tech, we oftentimes come across radios that don't work 100% right in some way shape or form - it's not perfect. So a lot of times - it's assembly. Even a loose nut on a volume control - the radio bouncing in the truck and one day - its' fine - the day after a trip to New York, it's acting like a piece of carp...noisy receive cutting in and out - talkback too loud one moment - next bump you now have echo on instead...
Ok, so loose parts or parts not making proper contact for SHIELDING can also take a radio from an excellent performer onto the biggest doorstop you have in your home because it just doesn't work like it should.
Why, well, don't ask why, more like how...Do I fix this?
I'm not asking you guys to turn this into a "tool time" comedy event - but if you take some time to clean up, straighten - turn controls to check for smoothness or any roughness in operation or even lobbing - bent shaft stuff. You may need to take it in for service but if you have a moment to take it out of the mount and back inside on a table to remove the covers you may be able to repair a quirky problem by simply retightening the case to board screws and check for loose hardware, or wiring that is hanging loose from a broken zip tie.
I've seen Echo boards that came in squealing - all because then they tightened the screw that holds it to the tab, by the Mic audio chip - they forgot to position the board properly - centering it, even using a nylon washer - onto the screw hole and not letting the foil ground of the board, affect the foil to chassis case ground the radio has.
Although nothing big, you can run into some serious audio problems if you position the board incorrectly and the ground of the board, GROUNDS the whole radios' INSULATED FROM EARTH GROUND - thru it's wiring harness - WHAM - problems and noise galore...
The insulated ground the Cobra 2000s' Main PCB board has, protects it from the elements and the environment it's in, it's why you see those weird voltages - they not weird, you're measuring from spots that are not all connected together like they once were. Ground in one location may not be the same ground in another - so your meter reflects this and in a way - just tattled on the incorrectly reassembled radio.
Just carefully take it apart and reposition - a lot of times - with radios as old as these are. The place it sat "in" for so long, shows up like a bathtub ring, you just re-align to those "points of position" and retighten the screws - a lot of this goes away.
I hope this helps! Because it may just be from being taken apart and put back together with dirty connections are affecting it's behavior. Now, because of age, it needs to be put back together EXACTLY else you'll have some heavy cleaning and burnishing and possibly reflowing of solder to touch up the work to repair this symptom - so you can make the radio work right again.