24-05-2011, 02:52 PM
Hi Rob,
Firstly, the two caps you kindly sent me arrived today, are fitted, and have got my little toaster set back on song, so many thanks for that! Secondly, the working voltage rating of 350V was fairly standard for waxy caps, and only reflects their maximum working voltage - it is not a good indication as to what the actual voltage is at a particular point in a radio that the cap in that position has to contend with. To illustrate that, I've just checked the voltage on C17 on a DAC90a in my workshop, and the actual voltage is only 65V at that point. There are few points on a DAC90A where the voltage is much above 100V, eg, anode of V4 (UL41) is 190V, and anode of V5 (UY41 rectifier) is 222V AC. Hence, 350VW caps are very conservativly rated in that set. As I've said before, the crucial one is C22 (0.1uF) across the mains, which should either be dispensed with, or replaced by a Class X cap. (The one held in place by a clip on top of the chassis, front left).
That said, I do have a new 750 VW 390pF mica cap for C17, which I'll happily pop in the post to you if it helps. One good turn deserves another, so shout if you'd like it!
David
Firstly, the two caps you kindly sent me arrived today, are fitted, and have got my little toaster set back on song, so many thanks for that! Secondly, the working voltage rating of 350V was fairly standard for waxy caps, and only reflects their maximum working voltage - it is not a good indication as to what the actual voltage is at a particular point in a radio that the cap in that position has to contend with. To illustrate that, I've just checked the voltage on C17 on a DAC90a in my workshop, and the actual voltage is only 65V at that point. There are few points on a DAC90A where the voltage is much above 100V, eg, anode of V4 (UL41) is 190V, and anode of V5 (UY41 rectifier) is 222V AC. Hence, 350VW caps are very conservativly rated in that set. As I've said before, the crucial one is C22 (0.1uF) across the mains, which should either be dispensed with, or replaced by a Class X cap. (The one held in place by a clip on top of the chassis, front left).
That said, I do have a new 750 VW 390pF mica cap for C17, which I'll happily pop in the post to you if it helps. One good turn deserves another, so shout if you'd like it!
David
