Regarding the older Philips 6604, Iīm quite certain that the only way besides locating the original bulb (quite difficult to say the least), is to replace the lamp-holder with the new type.

And to sum up the discussion regarding the Philips 13139 and Osram 64615, I have done some further testing this week between the two bulbs and have concluded that the Osram bulbs is not in any way an adequate replacement for the Philips 13139. The enlarger simply gets to dark, 2-4 stops depending on what neg used and that is simply put, not ok. Is there anyone that have tried bulbs of any other brand in the V35 that has any other experience?

Anyway, donīt buy the Osram bulb, waste of money.