dac90a - to replace or leave alone??

[Yorkie]

Easiest way to check Rob is by substituting the valve for a known good one. Easier said than done if you don't have one of course, but whereas UL41 valves aren't noted for being long-lived, conversely, the smoothers in DAC90As weren't noted for being major suspects of hum, and rarely need changing. I had a DAC90A in which I changed the smoothers for a new BVWS new manufacture unit, which made not a jot of difference, then did what I should have done first - took a UL41 out of another DAC90A which didn't hum, and that cured the problem, so I kept the old smoother, used it in another radio and it worked fine.