Replacement capacitors for Murphy A104 - UK Vintage Radio Repair and Restoration Discussion Forum

Hamfisted · 10th Nov 2019, 11:31 am

Hello everyone, I'm a new member and my name is Mike.

I need some advice about the type of capacitors I should use to replace those in the radio I am about to restore. Can I replace all the non electrolytics with polypropylene? Otherwise, what should I use to replace each type already fitted to the set.

It's a Murphy A104 by the way, and I have the circuit diagram but there is not much to help me there with this problem.

Thanks in advance for any advice you may have, I hope I have posted this question in the right place!

Station X · 10th Nov 2019, 1:29 pm

Hello and welcome to the forums.

See here:-

https://www.vintage-radio.com/repair...apacitors.html

and here:-

https://www.vintage-radio.net/forum/...ad.php?t=88767

Don't replace any caps with values in pF. They probably won't need replacing and if you do replace them you'll upset the set's alignment.

FStephenMasek · 10th Nov 2019, 6:30 pm

You could also replace the electrolytic capacitors with modern film capacitors. The scan on Radio Museum is poor quality, but I think then are 10 MFD. If you use film capacitors there, make sure they have a reasonable AC rating and/or are rated for ripple. I generally buy such capacitors from Mouser, and I see that they have several locations in Europe.

Nanozeugma · 10th Nov 2019, 8:32 pm

Hi Mike.
For whatever reason, Murphy's manual for the A104 does not include a part list.
The large aluminium can electrolytics are however C38/39 a double 16uF unit
and C37 a single 8uF can.
16+16uF 500v 35mm twin electrolytics are readily available from various sources, Cricklewood being but one. A single 8uF can will be hard to source but the value is not
critical, a 10uF fitted inside the original can (or under the chassis) would do.
The value of C39 should not exceed 16uF as this is the maximum value specified for
the UU6 rectifier.
As regards the waxed paper, non polarised capacitors, you could use yellow polypropylene axial types or brown radial metallised polypropylene types. A 630vdc rating would be more than adequate, excepting perhaps for C36 across the audio output transformer which should ideally be rated at 1000v.

Hamfisted · 11th Nov 2019, 9:59 pm

Thank you all so much for the advice. I am feeling more confident and ready to make a start on the restoration, Watch this space! 73's.

Graham, thanks for the links you posted, much appreciated.

10th Nov 2019, 11:31 am	#1
Hamfisted Retired Dormant Member Join Date: Nov 2019 Location: Cambridge, Cambridgeshire, UK. Posts: 2	Replacement capacitors for Murphy A104 Hello everyone, I'm a new member and my name is Mike. I need some advice about the type of capacitors I should use to replace those in the radio I am about to restore. Can I replace all the non electrolytics with polypropylene? Otherwise, what should I use to replace each type already fitted to the set. It's a Murphy A104 by the way, and I have the circuit diagram but there is not much to help me there with this problem. Thanks in advance for any advice you may have, I hope I have posted this question in the right place!

10th Nov 2019, 1:29 pm	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Repalcement capacitors for Murphy A104 Hello and welcome to the forums. See here:- https://www.vintage-radio.com/repair...apacitors.html and here:- https://www.vintage-radio.net/forum/...ad.php?t=88767 Don't replace any caps with values in pF. They probably won't need replacing and if you do replace them you'll upset the set's alignment. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

10th Nov 2019, 6:30 pm	#3
FStephenMasek Pentode Join Date: Jul 2011 Location: Mission Viejo, California, USA Posts: 144	Re: Repalcement capacitors for Murphy A104 You could also replace the electrolytic capacitors with modern film capacitors. The scan on Radio Museum is poor quality, but I think then are 10 MFD. If you use film capacitors there, make sure they have a reasonable AC rating and/or are rated for ripple. I generally buy such capacitors from Mouser, and I see that they have several locations in Europe.

10th Nov 2019, 8:32 pm	#4
Nanozeugma Heptode Join Date: Nov 2017 Location: London, UK. Bury, Lancashire quite regularly :) Posts: 611	Re: Replacement capacitors for Murphy A104 Hi Mike. For whatever reason, Murphy's manual for the A104 does not include a part list. The large aluminium can electrolytics are however C38/39 a double 16uF unit and C37 a single 8uF can. 16+16uF 500v 35mm twin electrolytics are readily available from various sources, Cricklewood being but one. A single 8uF can will be hard to source but the value is not critical, a 10uF fitted inside the original can (or under the chassis) would do. The value of C39 should not exceed 16uF as this is the maximum value specified for the UU6 rectifier. As regards the waxed paper, non polarised capacitors, you could use yellow polypropylene axial types or brown radial metallised polypropylene types. A 630vdc rating would be more than adequate, excepting perhaps for C36 across the audio output transformer which should ideally be rated at 1000v. __________________ Thermionic Emission, warms the cockles of your tubes.

11th Nov 2019, 9:59 pm	#5
Hamfisted Retired Dormant Member Join Date: Nov 2019 Location: Cambridge, Cambridgeshire, UK. Posts: 2	Re: Replacement capacitors for Murphy A104 Thank you all so much for the advice. I am feeling more confident and ready to make a start on the restoration, Watch this space! 73's. Graham, thanks for the links you posted, much appreciated.