There's a lot in the message, but thought this thread was about Cobra 25's ...
The AGE of those caps - and their ESR you're seeing now, is about time for them to give up - will need a recap.
I read you did change a lot of them so good job, I'm also confirming with you why they should be changed.
They will fail and if not taken care of, those caps can burn out the parts they work with - take out the stage if you try to keep them in there. Best to get rid of the older "grey can" caps - replace with new - it would not hurt to locate some 105C Heat/Temp rated types. Their a better quality - you might like the results better when it comes to audio.
Now you showed me some pics of the Old 29 you're working on, or the other working on, either way it seems you're getting a better handle on things and the issues around the abuse it got - good to see you're sticking with it.
The Coil Can without the slug, couldn't find any reference in your post, then I see you said POTS - I think you mean the IF can - they removed the slug - that seems to be one of the many issues you have - no slugs to tune/change the tuning within the coil.
Is there a Fix for that? I don't know - might have to scavenge one off of a donor radio and see if it will work - no guarantees.
Now, D11 in a Cobra 29 is the LIMITER Diode, hope you installed it correctly. If it's not, it Won't let you talk, but you make a carrier - just no audio to go with it.
The TDA7310's those Mixer Amps - Cobra still kept a lot of the older design, but made a lot of resistor changes to match their newer supplier that replaced these. So if you have an older schematic you might want to look thru the PLL' VCO of both radios to find the resistors that they changed.
Because to make the newer radio work with the older Mixer chips, the Bias may need to be adjusted to handle the older - better - Toshiba parts.
A side to side comparison might seem a waste of time, but in reality it's not. In comparing the two, Old versus New, you can see how they revised the VCO to fit a newer tighter design specification.
You do have some work ahead of you.
BTW - this thread is for the Cobra 25's - I think you should go back to the old 29 thread you started so we don't confuse the rest of the group looking for answers about their 25's.
