Victor H. Palmieri, the so-called "company doctor" who spent eight years turning the bankrupt Penn Central Corp. into a profitable concern, is trying to convince Baldwin-United Corp.'s lenders that he can do the same thing for the ailing financial services conglomerate.

In a telephone interview, Palmieri said he probably would have to sell Baldwin's mortgage companies and real estate holdings to revive the company.

Palmieri and his firm, Palmieri & Co., were hired last week by Baldwin-United. Palmieri was named president and chief executive of the Cincinnati company, with a five-year contract. He replaced Morley P. Thompson, who engineered Baldwin's growth from a tiny piano maker to a financial services conglomerate, using premium income from the company's insurance subsidiaries to finance most of the acquisitions.

Palmieri, 53, said that during the second week in June he expects to propose to creditors a plan to work Baldwin-United out of its troubles--a task that he said will take between three and five years.

But before Palmieri can work on Baldwin's long-term recovery, he will have to convince banks and other lenders to restructure the financial conglomerate's nearly $1 billion in debt. On July 15, $440 million of that debt is due to be repaid to the company's major bankers.

The banks already have granted Baldwin-United several extensions on repayment. Other lenders are trying to force Baldwin to pay back bonds and other securities early.

"Basically it's a situation that is very critical in the short term," Palmieri said. But he insisted he was hired to nurse Baldwin back to health, not "to liquidate it."

But to generate needed cash, Palmieri said, Baldwin probably will have to sell its mortgage companies and real estate holdings.

Palmieri also said he is meeting with insurance regulators, who are as nervous as Baldwin's lenders.

The regulators have put up roadblocks to former president Thompson's old tactics of tapping the premium income of insurance subsidiaries by selling them affiliated securities.

Thompson's strategy, which turned a tiny piano manufacturer into a $9.6 billion financial services conglomerate, began to unravel in early 1982 when regulators stopped Baldwin from tapping premium income to pay $1.17 billion to buy MGIC Investment Corp., the nation's biggest mortgage insurer. Thompson had to turn to his banks to borrow nearly $700 million, $440 million of which it still cannot repay.

Regulators are concerned because so much of the insurance companies' assets are tied up in Baldwin-affiliated securities that the insurance subsidiaries would have troubles paying off all their claims if policyholders cashed in at the same time. Insurance companies are supposed to have reserves--usually held as stock, bond and money market investments--sufficient to pay off all potential claims at any given time.

Because of Baldwin's highly publicized financial difficulties, the company has stopped selling its hottest product--the single premium deferred annuity--which generated more than $3 billion in premiums in 1981 and 1982.

In return for a one-time payment-usually between $5,000 and $100,000--the insurer guaranteed a high, tax-deferred return that begins to pay back to the investor at some point in the future.