Richard I have a 605 which may be quite different but I have a 75W bulb. I got this because ironically I was getting too short an exposure time for colour prints with 100W which is what Durst recommends for the 605. Certainly with dichroic head filtration a 100W wasn't too powerful for B&W printing. I am no electrical expert and we have 240V here in the U.K. but I am sure I'd struggle with 50W. This seems too low a wattage assuming my 605 is comparable with your 601

pentaxuser