Bush VHF70 Capacitor identification. - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Argus25 · 3rd May 2019, 12:00 pm

I would replace that 0.05uF with a 0.047uF 1000v rated Polyester. If you stick an X2 in there most likely you will find as time goes by its capacitance will drop off and you will simply see the lamps dim off. I have performed this "experiment" many times.

Though some X2's are better in this respect as the film is not as badly damaged by voltage spikes, but you are still better off with a higher voltage rated capacitor. If there is room , go for a 1200V to 1500v rated polyester. And, if you are worried about it shorting out one day (which it won't with that voltage rating) you can put a 100mA fuse in series with it.

Argus25 · 3rd May 2019, 12:37 pm

...ignore the remark about the lamps dimming off in my post above.

Northyorks1 · 3rd May 2019, 4:25 pm

Thanks for all your replys much appreciated. I will fit either x class or high voltage cap, any advice on which would be best.

Ian

julie_m · 3rd May 2019, 4:34 pm

There is a wirewound resistor limiting the fault current to c.1A, so in this case a class X capacitor is not strictly required.

Northyorks1 · 3rd May 2019, 7:57 pm

Thanks for advice from Julie and also Argus25 from the land down under.

ms660 · 3rd May 2019, 9:09 pm

Looking at the Trader sheet, if C65 goes short circuit I make it circa 8 Amps fault current once the lamps have gone pop.

Lawrence.

3rd May 2019, 12:00 pm	#21
Argus25 No Longer a Member Join Date: Oct 2016 Location: Maroochydore, Queensland, Australia. Posts: 2,679	Re: Bush VHF70 Capacitor identification. I would replace that 0.05uF with a 0.047uF 1000v rated Polyester. If you stick an X2 in there most likely you will find as time goes by its capacitance will drop off and you will simply see the lamps dim off. I have performed this "experiment" many times. Though some X2's are better in this respect as the film is not as badly damaged by voltage spikes, but you are still better off with a higher voltage rated capacitor. If there is room , go for a 1200V to 1500v rated polyester. And, if you are worried about it shorting out one day (which it won't with that voltage rating) you can put a 100mA fuse in series with it.

3rd May 2019, 12:37 pm	#22
Argus25 No Longer a Member Join Date: Oct 2016 Location: Maroochydore, Queensland, Australia. Posts: 2,679	Re: Bush VHF70 Capacitor identification. ...ignore the remark about the lamps dimming off in my post above.

3rd May 2019, 4:25 pm	#23
Northyorks1 Heptode Join Date: Mar 2018 Location: Saltburn, North Yorkshire, UK. Posts: 626	Re: Bush VHF70 Capacitor identification. Thanks for all your replys much appreciated. I will fit either x class or high voltage cap, any advice on which would be best. Ian

3rd May 2019, 4:34 pm	#24
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Bush VHF70 Capacitor identification. There is a wirewound resistor limiting the fault current to c.1A, so in this case a class X capacitor is not strictly required. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

3rd May 2019, 7:57 pm	#25
Northyorks1 Heptode Join Date: Mar 2018 Location: Saltburn, North Yorkshire, UK. Posts: 626	Re: Bush VHF70 Capacitor identification. Thanks for advice from Julie and also Argus25 from the land down under.

3rd May 2019, 9:09 pm	#26
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Bush VHF70 Capacitor identification. Looking at the Trader sheet, if C65 goes short circuit I make it circa 8 Amps fault current once the lamps have gone pop. Lawrence.