BERLIN — German pubcaster ZDF expects to close the year with a budget surplus of 164.6 million marks ($92.5 million). ZDF director Dieter Stolte said the network, which should have a 73.5 million mark ($41 million) surplus in 1998, will likely be debt-free by the end of 1998.ZDF racked up a deficit of $164 million in 1996. Stolte attributes the pubcaster’s financial troubles to sinking ad revenues. A rise in the compulsory viewing fees paid by German households has helped refill ZDF’s coffers this year, as have personnel reductions and other economizing measures. The pubcaster will have a 1998 budget of $1.5 billion, more than 60% of which will be spent on programming.