Prolly unrelated to your problem. But I learned something the other day when adjusting brakes on my 80s fuji roadie. Was riding to work when the rear brake just 'disappeared.' i.e. lever bottoms out against bar with no effective braking. Ok. Got around to looking at it the next day & after adjusting the cable, noticed a little lever on the piece where the rear-most piece of cable housing ends. Basically it looks like you 'open' this lever, adjust brakes, then close this lever to snug everything up. Note, this is for 20+ year old U brakes.