Cathode bypass capacitor. - UK Vintage Radio Repair and Restoration Discussion Forum

BigClick · 31st Dec 2015, 1:36 pm

Hi,

I need to replace a 25uf 12v electrolytic capacitor. It is the cathode bypass for an EL84.

Will a 30uf 50V bipolar do the same job or will the sound be degraded?

Is there a better equivelant out there

many thanks

ValvoStef · 31st Dec 2015, 2:05 pm

Hi BigClick,

Considering whe broad tolerance range of electrolytic capacitors I would say it won't matter that much. Just try and listen, but I think it will work.

BR

Stef.

Station X · 31st Dec 2015, 2:06 pm

If you want a closer match use 22uF.

31st Dec 2015, 2:12 pm

If the 30uF bipolar is what you have in stock use it, it will be fine. If not in stock it would be cheaper to buy a 22uF 12 volt part (or even 33uF).

BigClick · 31st Dec 2015, 2:23 pm

thanks again folks good info and fast replies

I dont have any components as yet, I am doing a list at the moment and I I cant find a 22uF 12 volt on the Cricklewood site, but it doesnt mean they dont have it lol.

The bipolar 30uF 50V is the nearest I have seen on the site.

Station X · 31st Dec 2015, 2:27 pm

This'll do the job:-

http://www.cricklewoodelectronics.com/22M35.html

If you don't want to use a radial component this'll cost a bit more:-

http://www.cricklewoodelectronics.com/22A100.html

Don't waste money on a bipolar component.

turretslug · 31st Dec 2015, 3:02 pm

A 33uF 16V or even 25V electrolytic should be almost trivially cheap from most suppliers, and will be very compact. Do you have a Maplin's nearby?- I know they might be a bit infra-dig in the eyes of hard-core electronics constructors but they ought to be able to come up with something. If you can find a 105 degree rated component, rather than 85 degrees, go for that- even if the location doesn't get to 85 degrees, many valve chassis eventually get pretty warm and the higher temperature component will have a substantially better chance of a long life. Avoid strange-name bargain components from auction sites....

Edit: Just followed Graham's links- they'll be fine.

31st Dec 2015, 1:36 pm	#1
BigClick Hexode Join Date: Dec 2015 Location: Walsall, West Midlands, UK. Posts: 327	Cathode bypass capacitor. Hi, I need to replace a 25uf 12v electrolytic capacitor. It is the cathode bypass for an EL84. Will a 30uf 50V bipolar do the same job or will the sound be degraded? Is there a better equivelant out there many thanks

31st Dec 2015, 2:05 pm	#2
ValvoStef Hexode Join Date: Mar 2014 Location: Fareham, Hampshire, UK. Posts: 482	Re: cathode bypass capacitor Hi BigClick, Considering whe broad tolerance range of electrolytic capacitors I would say it won't matter that much. Just try and listen, but I think it will work. BR Stef. __________________ Failing to prepare is preparing to fail ...

31st Dec 2015, 2:06 pm	#3
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: cathode bypass capacitor If you want a closer match use 22uF. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

31st Dec 2015, 2:12 pm	#4
Guest Guest Posts: n/a	Re: cathode bypass capacitor If the 30uF bipolar is what you have in stock use it, it will be fine. If not in stock it would be cheaper to buy a 22uF 12 volt part (or even 33uF).

31st Dec 2015, 2:23 pm	#5
BigClick Hexode Join Date: Dec 2015 Location: Walsall, West Midlands, UK. Posts: 327	Re: cathode bypass capacitor thanks again folks good info and fast replies I dont have any components as yet, I am doing a list at the moment and I I cant find a 22uF 12 volt on the Cricklewood site, but it doesnt mean they dont have it lol. The bipolar 30uF 50V is the nearest I have seen on the site.

31st Dec 2015, 2:27 pm	#6
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: cathode bypass capacitor This'll do the job:- http://www.cricklewoodelectronics.com/22M35.html If you don't want to use a radial component this'll cost a bit more:- http://www.cricklewoodelectronics.com/22A100.html Don't waste money on a bipolar component. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

31st Dec 2015, 3:02 pm	#7
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,396	Re: cathode bypass capacitor A 33uF 16V or even 25V electrolytic should be almost trivially cheap from most suppliers, and will be very compact. Do you have a Maplin's nearby?- I know they might be a bit infra-dig in the eyes of hard-core electronics constructors but they ought to be able to come up with something. If you can find a 105 degree rated component, rather than 85 degrees, go for that- even if the location doesn't get to 85 degrees, many valve chassis eventually get pretty warm and the higher temperature component will have a substantially better chance of a long life. Avoid strange-name bargain components from auction sites.... Edit: Just followed Graham's links- they'll be fine. Last edited by turretslug; 31st Dec 2015 at 3:12 pm.