UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - When is a capacitor not across the mains.

ChristianFletcher · 13th Jan 2021, 6:14 pm

I’m working on a KB10 mark 2. This has a capacitor C21 installed across the mains but has 150 ohms in series with it. Is this still an across the mains capacitor. I wondering if ideally it would be Y rated as a failure would likely light up the 150ohm resistor but wouldn’t initially blow the fuse with perspective fault current of 1.5 amps. I assume the resistor wouldn’t last very long as it tries to dissipate 350 watts but perhaps long enough to start a fire. I am guessing a failed short circuit rectifier would have a similar result etc.

I suggest Y rated as X rated capacitors are designed to fail short circuit and operate the circuit protection.

I had actually ordered a Xrated capacitor as I thought initially I had the mark 1 version and this does have the capacitor directly across the mains supply.

I wouldn’t normally worry about this but this radio is for a friend and so they may not take care in operating the radio as carefully as I would or do not know about the risk associated with old equipment. I suspect I’m asking an impossible question regards risk here.

Thanks Chris

13th Jan 2021, 6:14 pm	#1
ChristianFletcher Heptode Join Date: Dec 2003 Location: South Yorkshire, UK. Posts: 900	When is a capacitor not across the mains. I’m working on a KB10 mark 2. This has a capacitor C21 installed across the mains but has 150 ohms in series with it. Is this still an across the mains capacitor. I wondering if ideally it would be Y rated as a failure would likely light up the 150ohm resistor but wouldn’t initially blow the fuse with perspective fault current of 1.5 amps. I assume the resistor wouldn’t last very long as it tries to dissipate 350 watts but perhaps long enough to start a fire. I am guessing a failed short circuit rectifier would have a similar result etc. I suggest Y rated as X rated capacitors are designed to fail short circuit and operate the circuit protection. I had actually ordered a Xrated capacitor as I thought initially I had the mark 1 version and this does have the capacitor directly across the mains supply. I wouldn’t normally worry about this but this radio is for a friend and so they may not take care in operating the radio as carefully as I would or do not know about the risk associated with old equipment. I suspect I’m asking an impossible question regards risk here. Thanks Chris Attached Thumbnails __________________ Every Silver Lining Has Its Cloud https://youtube.com/channel/UCvBpiuUUnErJlNBm6DWb3Ww