Amid self-conscious cracks about the political corrupt*ion trial of Maryland Gov. Marvin Mandel, the Maryland General Assembly opened its 1977 session today votes on whether to override any of Mandel's 1976 bill vetoes.

The nervous joking was just about the only reminder of the still unresolved corruption charges as the legislature was reunited in its usual festive mood.

Many of the legislators had testified in Mandel's trial about a veto override of a racetrack bill that occured five years ago today, and as the Senate completed its first override vote today. Senate President Steny H. Hoyer (D-Prince George's) jokingly cautioned them.

"I want you all to remember what happened during that proceeding" Hoyer said. "So you can recall it with clarity two or three years from now."

Asked about the conspicious absence from the lobbies today of Mandel's chief lobbyists, Ronald Schreiber, Maurice Eyatt and Frank Harris. State Sen. Victor Crawford (D-Montgomery) quipped: "The're no racetrack legislation today." Crawford has testified against Mandel during the now aborted corruption trial.

The General Assembly did not complete its voting on any single override today although each house did independently vote to override several relatively minor vetoes on 1976 bills. The opposite house must approve the override as well to enact a measure.

Basically, opening day is an occasion for levity and renewal of acquaintances parties and speech making, in which legislators who fought bitterly at the end of last year's session bestow generous praises on one another. It is a day when most are content to sit and listen to a 15-minute description of Maryland's inaugural parade float.

Although some features of the scene here were different from previous years, most notable were the things that remained the same.

Sen. Edward T. Conroy (D-Prince George's) wore the three-piece blue suit that was his favorite last year, with the vest that does no quite cover his respectable sized belly; the loquacious Del. Charles Blumenthal, another Prince George's Democrat, made impassioned speeches in favor of overriding a dozen vetoes, with familiar results for him: on one bill, the veto was upheld by a vote of 132 to 1.

The sense of continuity apparently was too much for Sen. Roy N. Staten (D-Baltimore County), who as Senate majority leader reads Mandel's veto messages on all the bills rejected by the governor.

After the Senate had at long last finished voting on all 39 of the bills Manded had vetoed, Staten rose to his feet once again.

"What bill is this on.Mr. president?" he asked Hoyer. "We're finished, Mr. majority leader," replied the Senate president. "Oh," said Staten, quickly resuming his seat.

Over in the House of Delegates, the machine that automatically records and counts the legislators' votes (green for yes, red for no) broke down with four vetoed bills still to be acted upon.

As workmen struggled unsuccessfully to fix the machine, assistant House reading clerk Lawrence Goldstein began the mumbo-jumbo speed reading of bill being introduced in the new session.

The House then passed its first and only resolution of the day, eulogizing Del. Murray Abramson, who died last month. His wife, Helaine, was given a standing ovation and a letter to the delegates from her was, in the jargon of the legislative body, ordered "journalized," or recorded in the written record of the proceeding.

Abramson's successor was not sworn in, however, because of a dispute that has gone to court.

Traditionally in Baltimore, the widow of a deceased delegate is awarded the office for the remainder of the term, and Abramson's wife had sought the seat.

The three-member Democratic Central Committee Abramson's neighborhood rejected Mrs. Abramson's bid last week on a 2-to-1 vote, opting instead for James Dorf, the 21-year-old grandson of Baltimore political boss Jack Pollack. The action was blocked, however, because of a challenge to residency of Dorf's sister, Jayme, a committee member who cast the deciding vote in favor of her kid brother.

Little official business was conducted following the adjournments. A couple of House committees held brief meetings, debating such issues as how much each member should kick into the food kitty $3 for members of the House Economic Matters Committee, $5 for Environmental Matters, if committees should build a lunch-hour into their hearing schedules and an announcement that an apartment leased to a legislator during the last session ("it had hot and cold running . . . " said the spokesman) was available again this year.

One difference was the decision by House Democrats to open their party caucuses to the public. This break with hundreds of years of tradition was not overwhelmingly popular, however, as the best way to choose House leadership. House Speaker John Hanson Briscoe (D-St. Marys) said he was "sort of saddened" by the loss of "this last vestive of legitimate privacy."

In considering vetoes today, the Senate acted only on bills that originated in the Senate last year, and the House acted only on House bills. The Senate voted to override five vetoes, including one on a bill to mandate postrelease assistance for state mental patients, and one to require local school boards to reveal how much they spend on special education.

The House voted to override two vetoes, one on a bill to increase the number of truck-weighing stations from three to five, and one on a bill that would require each patient in a state-licensed institution for the mentally retarded to be given a personal plan of care.

On Thursday, the House will vote on whether to override vetoes on bills that originated in the Senate, and the Senate will vote on vetoed House veto overrides by three-fifths margins bills. Both chambers must approve for the overrides to become effective.