Kirby G4 power problem?

Hi, we have a Kirby G4, had it for 15 years ish now and its been fantastic, recently it has been working intermittently, when your using it the power will cut out, then you give the cable a bit of a wobble and a knock it starts but it has now died totally, i have taken the power cable from the hoover and tested it and that is fine, I have removed the casing head to see if i can have a go at it but stopped as i don't want to knacker it, our local repairer doesn't repair Kirby vacuum's and my wife refuses to allow Kirby the company into our house any more as she says the have taken the p--s for the years they have been servicing and so called repairing phantom problem, can you offer any advice about having it repaired or having a go myself.

Thanks

Paul