[RodB]

I just checked back to look at your photos to see what type electrolytic caps are in the chassis. If they were the aluminum container type then the outside can would be negative. For the dry paper/cardboard covered type like you have you'll have to rely on the schematic and the markings on the piece itself. I don't remember seeing one that had a negative wire that wasn't black. But you should always verify (ASSUME). So follow the black wire to where it is connected and find that connection in the schematic. Once you're there (schematic) you can see what the drafting person used to designate the negative lead. It was all up to what they wanted to use that week. In the early days, they used just the standard capacitor symbol. At some point they started using a different symbol for electrolytics and the Bracket ( [ ) laying flat became the commonly used negative. But not always; some egos get in the way of progress and flip the symbols. It wasn't a persistent discipline. Anyway, the best way is to verify with the schematic. I'll dig one up and check out the symbols used for your radio. I can come over and help, I've always wanted to see Maine.

Something I do when replacing crumbling insulated wire is not remove the wire but lift one end and run a piece of spaghetti insulation or heat shrink tube down the wire then reconnect it. It cuts down the error rate.