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Old 11th Nov 2012, 4:33 pm   #1
chompy1
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Default Capacitor replacement for valve TV's

Hi All,

When it comes to replacing wax capacitors that have ratings of up to 400 volts,
is it safe to use X2 class polyester film capacitors that have a rating of 275 volts?

Cheers, Paul
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Old 11th Nov 2012, 4:50 pm   #2
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Default Re: Capacitor replacement for valve TV's

In a word no, X2 capacitors are designed only for connection across the mains supply and have special characteristics to optimise them for that position.

The voltage rating would probably be OK (it's an AC rating on an X2 component and DC on the old ones) but all the same it is better to use the proper thing, suitable capacitors are widely available.
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Old 11th Nov 2012, 4:57 pm   #3
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Default Re: Capacitor replacement for valve TV's

Although the above is true I would have no problem with fitting an X2 rated at 275 AC in place of a < 400 volt wax capacitor if nothing else was to hand.

Colin M
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Old 11th Nov 2012, 5:56 pm   #4
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Default Re: Capacitor replacement for valve TV's

Thanks for your advice guys. The reason I ask is because I have a Bush TV-56 that I ordered replacement capacitors for from The Vintage TV and Wireless company in Norwich.

When I ordered them, I specifically asked for capacitors with a rating of at least 500 volts, but they sent me X2 polyester film capacitors with a rating of 275 volts, so I just assumed they would be suitable and soldered them in.

Although the TV is working well, would you guys recommend that I order 630V rated capacitors for it?

Cheers, Paul
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Old 12th Nov 2012, 10:29 am   #5
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Default Re: Capacitor replacement for valve TV's

Hi Paul

If you have replaced caps who's DC rating is 400 volts or less, then I would leave them.

Others may not agree, so see what other opinions you get before making your decision.

Colin M
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Old 12th Nov 2012, 12:29 pm   #6
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Default Re: Capacitor replacement for valve TV's

ok, thanks Colin. If I do decide to change them, which class would be best to go for?

Cheers, Paul
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Old 12th Nov 2012, 12:39 pm   #7
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Default Re: Capacitor replacement for valve TV's

Useful info on replacement capacitor types here:-

http://www.vintage-radio.com/repair-...apacitors.html
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Old 12th Nov 2012, 2:49 pm   #8
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Default Re: Capacitor replacement for valve TV's

Quote:
Originally Posted by chompy1 View Post
ok, thanks Colin. If I do decide to change them, which class would be best to go for?

Cheers, Paul
Use the yellow LCR type which is at the top of the list of replacement capacitors when you follow the link provided by Graham.

Colin M
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Old 12th Nov 2012, 3:08 pm   #9
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Default Re: Capacitor replacement for valve TV's

X2 capacitors should be able to routinely withstand peaks up to or above 700 volts and incidental peaks up to thousands of volts so they can be used to replace normal 630V capacitors in many cases. However they were never constructed to carry a significant current all the time. Also higher or faster peaks can cause 'self healing incidents'. Hence they sometimes loose their capacity over the years when used in series power supply designs such as the Philips Senseo.

I wouldn't recommend using X2 capacitors outside mains filters, but as others have said they will probably be okay in most 'light duty' coupling and decoupling applications.
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Old 12th Nov 2012, 3:56 pm   #10
robjkmannering
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Default Re: Capacitor replacement for valve TV's

You realise that the owner of the Vintage Tv and Wireless company is a member on here.
PM him if you need clarification of what he has sent.

Regards,
Rob
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Old 12th Nov 2012, 4:17 pm   #11
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Default Re: Capacitor replacement for valve TV's

In general I agree with Colin. X2 caps have to conform to a different set of parameters than standard polyester caps but in most cases the construction is very similar. They should be fine for standard coupling and decoupling applications in valve circuits. The 275V rating is AC and they should be fine up to about 400V DC or even more.

The main reason people don't routinely use X2 caps for these applications isn't that they're not up to the job, it's that they cost more and are relatively bulky.
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Old 13th Nov 2012, 1:29 pm   #12
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Default Re: Capacitor replacement for valve TV's

Thanks for your advice guys. I wasn't aware that the owner of The Vintage TV and Wireless Company is a member of this forum. How often does he use this forum?

Cheers, Paul
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Old 13th Nov 2012, 10:49 pm   #13
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Default Re: Capacitor replacement for valve TV's

If you look at the datasheets for X2 caps they often give a DC rating as well. From experience most 275VAC metallised polypropylene X caps would be rated around the 630Vdc mark.
Obviously some TV capacitors have a much higher DC rating than that eg 1500 or 2000VDC in the case of a lop tuning cap but that is a different matter and substitutes should be carefully thought through!
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Old 29th Jun 2013, 11:26 pm   #14
chompy1
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Default Re: Capacitor replacement for valve TV's

Thanks Kevin

Please can the moderators close this thread.

Thanks, Paul
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Old 5th Jul 2013, 5:33 pm   #15
chompy1
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Default Re: Capacitor replacement for valve TV's

as the Bush TV-56 is working well with the X2 poly film caps, I've decided to leave them fitted and just replace them as and when needed.

Thanks chaps, Paul

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