Sam Hammam has stepped down as Cardiff City chairman after agreeing to sell his majority shareholding.
Ridsdale will head a new consortium at Cardiff City
Former Leeds chairman Peter Ridsdale has replaced Hammam in a deal that will see millions wiped off the club's multi-million pound debt.
The club said the move was needed to bring new investment to build a new 30,000-seater stadium.
The stadium project has been dogged by delays, but a "positive" announcement is expected on Tuesday.
A club statement said: "In order that the current debt levels can be reduced and then eradicated and for the Club to have additional working capital, an agreement has now been reached for a debt equity swap with institutional hedge funds, who have acknowledged the unique huge potential that exists with Cardiff City Football Club.
"Heads of funds have been agreed for the new injection of funds and the deal is expected to be concluded prior to Christmas."
It is hoped that with this injection of funds the club can now go on to commence the new stadium
Ridsdale joined the club last year as deputy executive chairman, and has been heavily involved in pushing through Cardiff's new stadium project.
The £35m project, which includes a 438,700 sq ft retail development on the 60-acre site, has been dogged by delays and negative publicity for many years.
Cardiff City council have been reluctant to give the project the go-ahead until the Bluebirds could provide assurances over the viability of their proposals.
But Cardiff are now hopeful that the takeover deal will ensure the club "can now go on to commence the new stadium and attain Premier League status."
Hammam took over as chairman six years ago, and transformed the Bluebirds from a lower division club into an outfit leading the chase to the Premiership.
The Lebanese-born businessman's dream had always been to build a new stadium for Cardiff, but he has now been forced to move aside to ensure the project is finally fulfilled.
He has been offered a position as honorary life president by the club in acknowledgement of the "indebtedness that everyone owes" him.
Since joining in 2000, Hammam has overseen two promotions but has seen the club acquire debts of £30m.
One of his lowest points came last year when Cardiff were forced to sell leading players Graham Kavanagh, Danny Gabbidon and James Collins to avoid going into administration.