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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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8th Oct 2011, 10:09 pm | #1 |
Hexode
Join Date: Oct 2003
Location: Near Glasgow, UK.
Posts: 309
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Goblin time spot power supply
This radio has two large mica 0.01 microF mica caps wired in series across the primary of the mains transformer marked C12 and C13 on the attached part of the circuit diagram. For safety reasons I thought I would replace them. As this seems to put 0.005 microF across the mains I thought I should use X2 types. However, the connecting point between the caps is connected to earth and so one is connected L to E and the other N to E and I then wondered if I should be using Y2 types. I suspect the correct type to use here is the X2 type but I would just like to confirm this. I am also wondering how critical the values are here. I do not have any 0.01 but I do have 0.033. Will 0.033 do here? The voltage ratings seem a bit confusing as they are marked 250V AC on one side and 275V AC on the other. They are made by "RIFA". I seem to remember reading that this type of cap can fail in a spectacular way. Has anybody had a bad experience with this make?
Regards, Ken. |
8th Oct 2011, 11:19 pm | #2 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: Goblin time spot power supply
If the capacitors are L & N to ground, they should be Y type. Only L-N with no ground connection is X type. I find it helpful to think of a pair of overhead lines for Line and Neutral, X goes across the lines and two Y caps in series across the lines with their centre point sagging a bit and connected to the ground underneath look like a Y. (That's the way my mind works, anyway).
The different voltage ratings on your X types will likely be different national standards requirements, though it's possible (read the markings carefully or consult the data sheet) that they may be X rated at 275V and Y rated at 250V.
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9th Oct 2011, 12:35 am | #3 | |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,087
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Re: Goblin time spot power supply
Quote:
Other, thermoplastic-cased RIFA types seem fine. |
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9th Oct 2011, 11:40 am | #4 | |
Hexode
Join Date: Oct 2003
Location: Near Glasgow, UK.
Posts: 309
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Re: Goblin time spot power supply
Thanks for the replies. I don't have any Y2 types but had a quick look at an old Maplin catalogue (2007) and they had them then. I'll try during the coming week to see if they still have them.
Quote:
Thanks for your help, Ken. |
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