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Old 24th Jun 2021, 8:38 pm   #21
Station X
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Default Re: Ekco U353. Wax Capacitors.

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I can't see a third capacitor which needs to be class X or Y, but no doubt someone will correct me.
C3 manufactures and Trader, Y2 Class.

(Post#9)

Lawrence.
C3 isn't 0.01uf 400vac 1000vdc, as specified by the OP though, but I take your point that it needs to be Class Y.
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Old 24th Jun 2021, 9:00 pm   #22
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Default Re: Wax Capacitor

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I said that one goes to valve base well it does not it goes to aerial earth point on earth connections and and chassis. The other goes from on off switch terminal to mains dropper and other from chassis to output transformer yellow speaker cable. I have pics. All are same value 0.01uf 400vac 1000vdc
I'd say pictures 1 and 3 are the tone correction capacitor which isn't shown on the circuit diagram. A 0.01uF 1000VDC polypropylene capacitor will be fine in that position.

https://www.cricklewoodelectronics.c...Capacitor.html

Picture 2 shows C1 which needs to be a 0.01uF Class Y type. There is no need for this to be rated at 1000V. I think they're normally rated at 275VAC.

Picture 4 shows C61 which needs to be a 0.01uF Class X type. Once again I think these are rated at 275VAC.

https://www.cricklewoodelectronics.com/CXR10N.html

Designations refer to the manufacturer's service sheet.
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Old 25th Jun 2021, 9:28 am   #23
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Default Re: Ekco U353. Wax Capacitors.

Quote:
Originally Posted by Station X View Post
Quote:
Originally Posted by ms660 View Post
Quote:
Originally Posted by Station X View Post
I can't see a third capacitor which needs to be class X or Y, but no doubt someone will correct me.
C3 manufactures and Trader, Y2 Class.

(Post#9)

Lawrence.
C3 isn't 0.01uf 400vac 1000vdc, as specified by the OP though, but I take your point that it needs to be Class Y.
Quote:
Originally Posted by Station X View Post
I'd say pictures 1 and 3 are the tone correction capacitor which isn't shown on the circuit diagram. A 0.01uF 1000VDC polypropylene capacitor will be fine in that position.
In the 1st photo in Post#7 it appears to show a wax capacitor connected between tag D on the output transformer (one of the loudspeaker connections) and chassis, if that's the case then it's connected across C3 if C3 is fitted (C3 wasn't fitted to the later production chassis according to the service info.) and if replaced it should be replaced with a Y Class type.

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Old 25th Jun 2021, 9:45 am   #24
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Default Re: Ekco U353. Wax Capacitors.

I've just realised that I have the Ferranti version of this set, the U1032. I changed the waxies years ago without giving it a second thought. I'll take a look inside later and see how the tone correction capacitor is wired.
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Old 25th Jun 2021, 10:05 am   #25
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Default Re: Ekco U353. Wax Capacitors.

There's no tone correction capacitor connected to the output transformer in the schematics I have.

There isn't one in this Ferranti U1032 either that I can see:

https://www.vintage-radio.net/forum/...1&d=1282575693

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Old 25th Jun 2021, 10:52 am   #26
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Default Re: Ekco U353. Wax Capacitors.

So what is that capacitor then. You say it's wired across C3, so it can't be that. Is there an undocumented capacitor? If so what is its function?
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Old 25th Jun 2021, 11:16 am   #27
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Default Re: Ekco U353. Wax Capacitors.

All I know is that if it's going to be replaced it should be replaced with a Y Class type if the extension loudspeaker sockets are still connected to the loudspeaker, C3 as originally fitted to the earlier chassis was mounted topside of the chassis according to the layout info.

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Old 25th Jun 2021, 11:28 am   #28
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Default Re: Ekco U353. Wax Capacitors.

So what capacitor do I use on the transformer. Or can I leave it without one or leave the old wax capacitor as it is
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Old 25th Jun 2021, 11:38 am   #29
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Default Re: Ekco U353. Wax Capacitors.

Take your pick:

https://uk.farnell.com/w/c/passive-c...ating-y=300vac

Other suppliers are available.

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Old 25th Jun 2021, 1:11 pm   #30
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Default Re: Ekco U353. Wax Capacitors.

One side of the loudspeaker in the Ekco U319 is also connected to chassis via a 0.01uF capacitor, so far as its function goes for the loudspeaker circuit I can only think that it's there for RF de-coupling purposes to prevent any RF picked up by an extension loudspeaker cable from being introduced into the -ve feedback winding and finding its way back to the input of the AF amplifier.

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Old 25th Jun 2021, 3:43 pm   #31
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Default Re: Ekco U353. Wax Capacitors.

Hi Dorian27, I think it is safest to replace it with the recommended part, which is designed to fulfill a safety role as well as a circuit role.

Those wax capacitors will bite you one day, so it is a worthwhile exercise that you are persevering with these changes!
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Old 25th Jun 2021, 4:15 pm   #32
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Default Re: Ekco U353. Wax Capacitors.

I took the back off my Ferranti U1032 which is similar to the Ekco U353.

All component references in what follows are from the manufacturer's service sheet for the Ekco U353.

Going right back to post #1 the OP queried three 0.1uF 1000VDC wax capacitors. These are:-

C1 wired from the signal earth socket to chassis. I had replaced this with a 0.01uF Class Y capacitor as shown in the picture.

C61 wired across the mains supply on the output side of the mains switch, or wired between one side of the mains supply on the output side of the mains switch and chassis, which amounts to the same thing electrically. I had replaced this with a 0.01uF Class X capacitor as shown in the picture.

An undocumented capacitor wired from the output transformer to ground. My set was not fitted with this capacitor. Perhaps it was only fitted to some sets? I've posted a picture showing the absence of this capacitor.

C3 has also been mentioned in this thread, but I don't think the OP queried it. It's 1800pF and mounted on the side of the VHF Tuner Unit at the end of the balanced pair of wires from the VHF aerial socket. I have not replaced this capacitor and it would not occur to me to replace a capacitor of this type and value. I've posted a picture of it for completeness. It would be interesting to know whether C3 is fitted to the OP's set.
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Old 25th Jun 2021, 4:39 pm   #33
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Default Re: Ekco U353. Wax Capacitors.

On my Ferranti U1032, manufacturers circuit.
C1, signal earth to chassis, I removed this as the earth socket connection would never be used but would have used a Y class if I had done.

C61 replaced with class X.

C3 was replaced with a class Y due to the possibility of its failure causing a danger if using an external aerial.

My set did not have the undocumented capacitor on the output transformer.
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