NEW YORK (CNN/Money) - Adelphia Communications Corp. expects to file for Chapter 11 bankruptcy protection soon, with a filing coming by Monday, as the troubled cable operator has reached an agreement to secure $1.5 billion in financing, a source familiar with situation told CNN/Money Friday.

Salomon Smith Barney and J.P. Morgan are arranging the $1.5 billion loan, which will help the company as it reorganizes, the source said.

Under Chapter 11, companies are protected from their creditors as they reorganize. Adelphia shareholders will likely lose their investment since they will be last in line to get paid. Secured creditors are first, followed by creditors whose loans have no collateral and then shareholders, according to the U.S. Bankruptcy Code.

Adelphia Communications said Thursday that it failed to make interest and dividend payments totaling almost $30 million, on top of missing a $51 million interest payment last week.

Coudersport, Pa.-based Adelphia, the nation's sixth-largest cable operator, has long been expected to file for bankruptcy protection. Earlier this month, Moody's Investors Service said it anticipated a bankruptcy filing from the cable operator to be imminent and at the same time, it downgraded Adelphia's junk-rated senior unsecured debt of about $4.9 billion to Caa2 from Caa1, its fourth-lowest grade. Moody's at that time said that Adelphia had about $19.3 billion in rated debt.

The Securities and Exchange Commission and federal grand juries in Pennsylvania and New York are also investigating Adelphia's finances. In March, it was disclosed that the Rigas family engaged in off-the-book borrowings to use Adelphia cash or assets to invest in a golf course and expand its personal cable assets. Last month, Adelphia ousted the Rigas family -- including co-founder and ex-CEO John Rigas -- from its board.

The cable operator has also failed to file its annual reports, which caused it to be booted off the Nasdaq. The delisting triggered covenants in some of Adelphia's convertible bonds, forcing the company to buy back about $1.4 billion in convertible debt.

Adelphia declined comment. J.P. Morgan and Citigroup also declined comment.