Marconi C10A smoothing caps replacement - UK Vintage Radio Repair and Restoration Discussion Forum

RojDW48 · 5th Mar 2021, 3:34 pm

I have a 1947 Marconi C10A radio, which I am proposing to use with a bluetooth receiver (nice audio stage). There is a bit more hum than I would like, so I propose to replace the smoothing and reservoir caps. Location is quite awkward - is it OK to solder the replacements to the tags under the existing can and thence to ground - ie, leaving the old caps in circuit?

Herald1360 · 6th Mar 2021, 1:10 am

Possibly or even probably but.....

To avoid the possibility of a future S/C failure of an old cap it would be better to try to make the +ve connections to the new caps by disconnecting the wires to the old ones and transferring them to the new. You can get away with assorted cable ties and bits of heat shrink to make it safe, or you could neaten it up a bit if there's room by soldering the mounting leg of a bit of 3-way tag strip onto one of the old capacitor tags* and using the other two tags for the +ve connections to the new ones.

* If there's room, of course, you could just screw the tag strip mount to the chassis!

mark pirate · 6th Mar 2021, 9:22 am

I would strongly advise not to leave the old caps in circuit, better to fit a tag strip for the new electrolytics and completely disconnect the originals, as they could short out in the future.

Mark

jonnybear · 6th Mar 2021, 10:58 am

Why not just restuf the original capacitor can with new capacitors? be wary of increasing capacity as those old rectifiers (don't like it up um) quote cpl Jones.
John

RojDW48 · 6th Mar 2021, 8:48 pm

Thanks for the advice gents. I bit the bullet this afternoon and it only took a couple of hours with assorted components pushed aside and masking tape tying back the wires (!) to replace the caps and disconnect the can. point taken about the doddery old rectifier - I can't see any evidence of previous repairs

not bad for 73 !! I must say I am very pleasantly surprised by the audio quality of this old thing, and it seems perfectly happy amplifying the output of a CD player.

Kentode · 7th Mar 2021, 11:24 am

That's handsome! I'm ten years younger and I've had several replacement parts.

Can you please post a picture with the doors shut? Where is the speaker/s?

RojDW48 · 7th Mar 2021, 2:03 pm

I'm one year younger and I wish I worked as well! The speaker is underneath in an angled extension to the cabinet. Interestingly the PU input, ext aerial socket, extension speaker output AND the switch for int/ext speaker are on a panel at the back, underneath and behind the speaker! Ergonomics not a major consideration for Marconi's post war design team it would seem!

Kentode · 7th Mar 2021, 2:41 pm

It makes a nice piece of furniture, all that's missing is a bottle of sherry and some glasses on top!

RojDW48 · 1st Jun 2021, 2:47 pm

This has become a fixture in the living room and even the Mem Sahib has fallen for it and switches on regularly (CD into the PU input). So I am truly impressed by the longevity - just he PS caps replaced and no evidence of previous repairs. I haven't looked at the speaker, which works well, but quite a few wires disappear into its fabric shroud - field coil - or just an external tx?

5th Mar 2021, 3:34 pm	#1
RojDW48 Nonode Join Date: Jun 2014 Location: Bristol, UK. Posts: 2,074	Marconi C10A smoothing caps replacement I have a 1947 Marconi C10A radio, which I am proposing to use with a bluetooth receiver (nice audio stage). There is a bit more hum than I would like, so I propose to replace the smoothing and reservoir caps. Location is quite awkward - is it OK to solder the replacements to the tags under the existing can and thence to ground - ie, leaving the old caps in circuit? __________________ '....don't go mistaking Paradise for that home across the road!' (Bob Dylan)

6th Mar 2021, 1:10 am	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Marconi C10A smoothing caps replacement Possibly or even probably but..... To avoid the possibility of a future S/C failure of an old cap it would be better to try to make the +ve connections to the new caps by disconnecting the wires to the old ones and transferring them to the new. You can get away with assorted cable ties and bits of heat shrink to make it safe, or you could neaten it up a bit if there's room by soldering the mounting leg of a bit of 3-way tag strip onto one of the old capacitor tags* and using the other two tags for the +ve connections to the new ones. * If there's room, of course, you could just screw the tag strip mount to the chassis! __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

6th Mar 2021, 9:22 am	#3
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: Marconi C10A smoothing caps replacement I would strongly advise not to leave the old caps in circuit, better to fit a tag strip for the new electrolytics and completely disconnect the originals, as they could short out in the future. Mark

6th Mar 2021, 10:58 am	#4
jonnybear Octode Join Date: Nov 2010 Location: Cullompton, Devon, UK. Posts: 1,435	Re: Marconi C10A smoothing caps replacement Why not just restuf the original capacitor can with new capacitors? be wary of increasing capacity as those old rectifiers (don't like it up um) quote cpl Jones. John

6th Mar 2021, 8:48 pm	#5
RojDW48 Nonode Join Date: Jun 2014 Location: Bristol, UK. Posts: 2,074	Re: Marconi C10A smoothing caps replacement Thanks for the advice gents. I bit the bullet this afternoon and it only took a couple of hours with assorted components pushed aside and masking tape tying back the wires (!) to replace the caps and disconnect the can. point taken about the doddery old rectifier - I can't see any evidence of previous repairs not bad for 73 !! I must say I am very pleasantly surprised by the audio quality of this old thing, and it seems perfectly happy amplifying the output of a CD player. Attached Thumbnails __________________ '....don't go mistaking Paradise for that home across the road!' (Bob Dylan)

7th Mar 2021, 11:24 am	#6
Kentode Octode Join Date: Mar 2015 Location: Yorkshire, England. Posts: 1,301	Re: Marconi C10A smoothing caps replacement That's handsome! I'm ten years younger and I've had several replacement parts. Can you please post a picture with the doors shut? Where is the speaker/s? __________________ Regards, Ken. BVWS member

7th Mar 2021, 2:03 pm	#7
RojDW48 Nonode Join Date: Jun 2014 Location: Bristol, UK. Posts: 2,074	Re: Marconi C10A smoothing caps replacement I'm one year younger and I wish I worked as well! The speaker is underneath in an angled extension to the cabinet. Interestingly the PU input, ext aerial socket, extension speaker output AND the switch for int/ext speaker are on a panel at the back, underneath and behind the speaker! Ergonomics not a major consideration for Marconi's post war design team it would seem! Attached Thumbnails __________________ '....don't go mistaking Paradise for that home across the road!' (Bob Dylan)

7th Mar 2021, 2:41 pm	#8
Kentode Octode Join Date: Mar 2015 Location: Yorkshire, England. Posts: 1,301	Re: Marconi C10A smoothing caps replacement It makes a nice piece of furniture, all that's missing is a bottle of sherry and some glasses on top! __________________ Regards, Ken. BVWS member

1st Jun 2021, 2:47 pm	#9
RojDW48 Nonode Join Date: Jun 2014 Location: Bristol, UK. Posts: 2,074	Re: Marconi C10A smoothing caps replacement This has become a fixture in the living room and even the Mem Sahib has fallen for it and switches on regularly (CD into the PU input). So I am truly impressed by the longevity - just he PS caps replaced and no evidence of previous repairs. I haven't looked at the speaker, which works well, but quite a few wires disappear into its fabric shroud - field coil - or just an external tx? __________________ '....don't go mistaking Paradise for that home across the road!' (Bob Dylan)