A U.S. District Court Judge yesterday agreed to a $25,000 release bond for one of three anti-Castro Cubans whose convictions in connection with the 1976 car bombing murder of former Chilean ambassador Orlando Letelier were reversed by a federal appeals court last Week.

The U.S. Court of Appeals ordered a new trial for Ignacio Novo Sampol, ruling that Judge Barrington D. Parker should have given him a separate trial from the other two defendants in the case because Ignacio Novo faced lesser charges. In that same opinion, the appeals court granted Ignacio Novo's request for release on bail and told Parker to fix the bond conditions.

At a hearing yesterday, Assistant U.S. Attorney E. Lawrence Barcella Jr. suggested to Parker that he set the same bond conditions for Ignacio Novo that had been in effect before his conviction in February 1979, for making false statements to a grand jury and for concealing information from prosecutors investigating the murder of Letelier and a colleague, Ronni K. Moffitt.

Parker agreed and said he would allow Ignacio Novo to reside in Miami with his wife, where he is expected to work as a travel agent.

In its decision last week the appeals court also reversed murder convictions against the two other defendants, Guillermo Novo Sampol and Alvin Ross Diaz, because evidence from informants who had been jailmates of the two men was improperly introduced at their trial. The appeals court also ordered new trials or those men.

Barcella told Parker yesterday that the prosecutor's office here has asked the Justice Department of approval to ask the full court of appeals or the U.S. Supreme Court to review the murder case involving the two men. If those appeals fail, Barcella said the government will then retry the murder case against Guilermo Novo and Diaz.