Cathode Bypass Value - UK Vintage Radio Repair and Restoration Discussion Forum

Barrie · 17th Aug 2008, 6:45 pm

Hi
I am recapping a philips 206A set, the output valve (EBL31) cathode bypass in quoted as 25uF -25 volt, can i use 22uF or 33uF without problems.
Barrie.

Steve_P · 17th Aug 2008, 6:47 pm

Yes, you can. No worries!

Cheers,

Steve P.

paulsherwin · 17th Aug 2008, 6:50 pm

As Steve says, this is not a critical component. You can remove it altogether and the radio will still work and possibly sound better, though the gain will be reduced which may matter in a short superhet. Anything in the 22uF-100uF range will be fine.

Paul

kalee20 · 17th Aug 2008, 6:55 pm

Yes, preferably the 33uF. Smaller values of cathode bypass capacitor will give you bass cut. Larger values will give you a level response down to a lower frequency. Of course, the bass roll-off is also governed by other factors, and in a good design it will be determined by components which are more predictable than the average electrolytic capacitor. That's why increasing the value should have no bad effect whatsoever.

Bear in mind the original Philips designers may have wanted a larger value in any case, and were constrained by cost to limit the value they specified to 25uF.

Barrie · 17th Aug 2008, 10:18 pm

Many thanks for the replies,(sorted)
regards Barrie.

17th Aug 2008, 6:45 pm	#1
Barrie Tetrode Join Date: Jun 2006 Location: Close to Luton Airport, Bedfordshire, UK. Posts: 95	Cathode Bypass Value Hi I am recapping a philips 206A set, the output valve (EBL31) cathode bypass in quoted as 25uF -25 volt, can i use 22uF or 33uF without problems. Barrie.

17th Aug 2008, 6:47 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Cathode Bypass Value Yes, you can. No worries! Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

17th Aug 2008, 6:50 pm	#3
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: Cathode Bypass Value As Steve says, this is not a critical component. You can remove it altogether and the radio will still work and possibly sound better, though the gain will be reduced which may matter in a short superhet. Anything in the 22uF-100uF range will be fine. Paul

17th Aug 2008, 6:55 pm	#4
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,082	Re: Cathode Bypass Value Yes, preferably the 33uF. Smaller values of cathode bypass capacitor will give you bass cut. Larger values will give you a level response down to a lower frequency. Of course, the bass roll-off is also governed by other factors, and in a good design it will be determined by components which are more predictable than the average electrolytic capacitor. That's why increasing the value should have no bad effect whatsoever. Bear in mind the original Philips designers may have wanted a larger value in any case, and were constrained by cost to limit the value they specified to 25uF.

17th Aug 2008, 10:18 pm	#5
Barrie Tetrode Join Date: Jun 2006 Location: Close to Luton Airport, Bedfordshire, UK. Posts: 95	Re: Cathode Bypass Value Many thanks for the replies,(sorted) regards Barrie.