Murphy A40C radio - UK Vintage Radio Repair and Restoration Discussion Forum

ELVISROY · 8th May 2018, 8:16 pm

Hi, I''m new, here and in England, and have just been given an A40C Murphy radio with original operating booklet. I've turned it on without an aerial plugged in it and you can here it going through the stations so it seems to work, but after about 4 minutes the transformer at the bottom starts smoking, so switched it off. Its a nice looking machine and has a smoked glass top.

paulsherwin · 8th May 2018, 8:56 pm

There are many possible faults. You shouldn't turn it on again unless it's been checked out by someone who knows what they're doing.

Cobaltblue · 8th May 2018, 8:58 pm

This is one of Murphys finest

Dont put power on again until you make some basic tests

Cheers

Mike T

Boater Sam · 8th May 2018, 9:19 pm

Mazda UU4 rectifiers have a habit of going short circuit, that cooks the mains transformer, to destruction if not hed off fast enough.
Please don't destroy it, this is a highly desirable radio.

high_vacuum_house · 8th May 2018, 9:21 pm

Sounds like one of the HT windings on the mains transformer has a shorted turn.

There is a similar mains transformer in the Murphy A30C which did the identical thing. Luckily these transformers can be dismantled fairly easily as they are held together with 2BA bolts/nuts and you can slide the bobbins out of the centre once the laminations have been removed.

I rewound mine on a home made coil winder and after reassembly all was well.

If the set has not been restored it probably needs going through properly to replace perished wiring and leaking capacitors especially in the sound output stage and power supply as can overload and destroy output/ rectifier valves and output transformer.

They work extremely well once restored. 2 big bottles in the push/pull amplifier and a 15" speaker.

Christopher Capener

Cobaltblue · 8th May 2018, 9:25 pm

Hi Elvisroy

So I am guessing Elvis is a particular interest and why not a great performer.

Thermionic is not far from you in Penzance and he is a very able restorer.

Send him a PM and see if he is prepared to help out.

By the way I grew up in Carbis Bay and my father is a Newlyn man

Cheers

Mike T

mister valve · 9th May 2018, 12:06 am

As mentioned above.... Don't power up until you have found out what is causing the Mains Transformer to 'cook'.

It could be the Transformer its self (with a shorted turn), or the Rectifier Valve, or the Reservoir and Smoothing Capacitors (Condensers) short circuit. Or indeed a short, or partial short some where else in the High Tension supply . So please do check these things out before 'plugging in' again. As you may cause much damage to your set if you don't !

John10b · 9th May 2018, 9:12 am

Just taken a look at circuit diagram, 14 valves, certainly an impressive wireless.
Cheers
John

marconi_pete · 9th May 2018, 10:08 am

A very impressive set indeed. As others have pointed out please don't power this up again until all relevant checks have been made and any relevant capacitors are replaced. Quite an interesting design with the dial glass on the top of the cabinet.

Thanks,
Peter

HamishBoxer · 9th May 2018, 10:52 am

Just a point I thought the circuit for this set (A40C) was on Paul's dvd but I have not found it on mine.

ukcol · 9th May 2018, 11:30 am

It is definitely on the DVD but not on the earlier CD-ROM.

HamishBoxer · 9th May 2018, 11:42 am

Ah,thank you I need to check and see which mine is as I thought it was a dvd.

It certainly says dvd,I better have another search.

Need to look more carefully,it is indeed there under A40!

Hartley118 · 9th May 2018, 11:43 am

There's an interesting comprehensive and complimentary review of the A40C in Wireless World March 1938, page 196 onwards http://www.americanradiohistory.com/...ld-1938-03.pdf . "Radio and Acoustic Performance under Efficient Control". It includes the circuit diagram together with complete descriptions.

It's an impressive example of the pre-war radio designer's art made to get the best out of the relatively high fidelity AM transmissions of those days.

However, it's not exactly the best example for starting a radio restoration hobby!

Martin

paulsherwin · 9th May 2018, 12:00 pm

Agreed, sorting one of these out will be extremely challenging for a beginner. Even experienced restorers and repairers will be unfamiliar with this level of complexity.

HamishBoxer · 9th May 2018, 12:17 pm

They do sound superb when restored though,worth every effort they need.Had mine many years when £20 would buy one!

No longer that cheap and the only real drawback is the weight of that speaker when moving them.

dave walsh · 9th May 2018, 12:18 pm

Great set and original. It's just a shame that he didn't get a "four minute/minuet" warning Paul as just a little reading around on here or elsewhere would have avoided/reduced the risk. Maybe there should be a banner on the site-If You Are New To Restoration Don't Do This etc!

Perhaps he will return for all the advice, a restorer or a sale?

Dave

ELVISROY · 9th May 2018, 12:29 pm

Hi Mike and all those who replied, i actually put it back on and it stopped smoking but i had radio stations playing last night bit crackly but it was a Bosnia channel im not sure if it was just accumulation of dust that made the smoke, dont want to spend any money on it just like the cabinet but if someone wants to buy it they can

HamishBoxer · 9th May 2018, 12:44 pm

Brilliant idea to have a new comer warning at the top of the site home page,even if it says do not plug-in.

ELVISROY · 9th May 2018, 8:56 pm

Sorry turned it on before i read this lot, but i picked up Bosnia station on it last night with a bit off wire stuck in the aerial hole. It has no smell off burning and no smoke. I think it could do with some Servisol on the channel changer, don`t think i would use it anyway as it costs too much to run 200wats, which means after 5 hours switched on you would use one unit off electricity.

Quote:

Originally Posted by Cobaltblue

Hi ElvisroySo I am guessing Elvis is a particular interest and why not a great performer.

Hi yes Elvis fan, iv had the radio on just now and picked Bosnia and a few other channels on 21m and with just a small bit of wire as aerial

mister valve · 30th Sep 2018, 11:04 pm

Shame you're at the other end of the country. If you still have the set, I would have been very interested in buying it. Trouble is I have no transport and it would cost an arm and a leg to get a removal company to get it up here (Blackpool).

They are fantastic sets, good performers and well made too, but like all sets of that age, restoration is a must before it is used; otherwise serious and expensive damage can be caused to it.

8th May 2018, 8:16 pm	#1
ELVISROY Retired Dormant Member Join Date: May 2018 Location: St. Ives, Cornwall, UK. Posts: 3	Murphy A40C radio Hi, I''m new, here and in England, and have just been given an A40C Murphy radio with original operating booklet. I've turned it on without an aerial plugged in it and you can here it going through the stations so it seems to work, but after about 4 minutes the transformer at the bottom starts smoking, so switched it off. Its a nice looking machine and has a smoked glass top.

8th May 2018, 8:56 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,944	Re: A40c murphy radio There are many possible faults. You shouldn't turn it on again unless it's been checked out by someone who knows what they're doing.

8th May 2018, 8:58 pm	#3
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,865	Re: A40c murphy radio This is one of Murphys finest Dont put power on again until you make some basic tests Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

8th May 2018, 9:19 pm	#4
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: A40c murphy radio Mazda UU4 rectifiers have a habit of going short circuit, that cooks the mains transformer, to destruction if not hed off fast enough. Please don't destroy it, this is a highly desirable radio.

8th May 2018, 9:21 pm	#5
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,935	Re: A40c murphy radio Sounds like one of the HT windings on the mains transformer has a shorted turn. There is a similar mains transformer in the Murphy A30C which did the identical thing. Luckily these transformers can be dismantled fairly easily as they are held together with 2BA bolts/nuts and you can slide the bobbins out of the centre once the laminations have been removed. I rewound mine on a home made coil winder and after reassembly all was well. If the set has not been restored it probably needs going through properly to replace perished wiring and leaking capacitors especially in the sound output stage and power supply as can overload and destroy output/ rectifier valves and output transformer. They work extremely well once restored. 2 big bottles in the push/pull amplifier and a 15" speaker. Christopher Capener __________________ Interests in the collection and restoration of Tefifon players and 405 line television

8th May 2018, 9:25 pm	#6
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,865	Re: A40c murphy radio Hi Elvisroy So I am guessing Elvis is a particular interest and why not a great performer. Thermionic is not far from you in Penzance and he is a very able restorer. Send him a PM and see if he is prepared to help out. By the way I grew up in Carbis Bay and my father is a Newlyn man Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

9th May 2018, 12:06 am	#7
mister valve Hexode Join Date: Aug 2009 Location: Blackpool, Lancashire, UK. Posts: 311	Re: A40c murphy radio As mentioned above.... Don't power up until you have found out what is causing the Mains Transformer to 'cook'. It could be the Transformer its self (with a shorted turn), or the Rectifier Valve, or the Reservoir and Smoothing Capacitors (Condensers) short circuit. Or indeed a short, or partial short some where else in the High Tension supply . So please do check these things out before 'plugging in' again. As you may cause much damage to your set if you don't ! __________________ If you live, the chassis was dead; if you're dead, the chassis was live !!!!

9th May 2018, 9:12 am	#8
John10b Nonode Join Date: Nov 2016 Location: Aberaeron, Ceredigion, Wales, UK. Posts: 2,884	Re: A40c murphy radio Just taken a look at circuit diagram, 14 valves, certainly an impressive wireless. Cheers John

9th May 2018, 10:08 am	#9
marconi_pete Hexode Join Date: Mar 2012 Location: London, UK. Posts: 347	Re: A40c murphy radio A very impressive set indeed. As others have pointed out please don't power this up again until all relevant checks have been made and any relevant capacitors are replaced. Quite an interesting design with the dial glass on the top of the cabinet. Thanks, Peter

9th May 2018, 10:52 am	#10
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: A40c murphy radio Just a point I thought the circuit for this set (A40C) was on Paul's dvd but I have not found it on mine. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

9th May 2018, 11:30 am	#11
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	Re: A40c murphy radio It is definitely on the DVD but not on the earlier CD-ROM.

9th May 2018, 11:42 am	#12
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: A40c murphy radio Ah,thank you I need to check and see which mine is as I thought it was a dvd. It certainly says dvd,I better have another search. Need to look more carefully,it is indeed there under A40! __________________ G8JET BVWS Archivist and Member V.M.A.R.S

9th May 2018, 11:43 am	#13
Hartley118 Nonode Join Date: Aug 2015 Location: Cambridge, Cambs. UK. Posts: 2,198	Re: A40c murphy radio There's an interesting comprehensive and complimentary review of the A40C in Wireless World March 1938, page 196 onwards http://www.americanradiohistory.com/...ld-1938-03.pdf . "Radio and Acoustic Performance under Efficient Control". It includes the circuit diagram together with complete descriptions. It's an impressive example of the pre-war radio designer's art made to get the best out of the relatively high fidelity AM transmissions of those days. However, it's not exactly the best example for starting a radio restoration hobby! Martin __________________ BVWS Member

9th May 2018, 12:00 pm	#14
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,944	Re: A40c murphy radio Agreed, sorting one of these out will be extremely challenging for a beginner. Even experienced restorers and repairers will be unfamiliar with this level of complexity.

9th May 2018, 12:17 pm	#15
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: A40c murphy radio They do sound superb when restored though,worth every effort they need.Had mine many years when £20 would buy one! No longer that cheap and the only real drawback is the weight of that speaker when moving them. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

9th May 2018, 12:18 pm	#16
dave walsh Dekatron Join Date: Jan 2006 Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex. Posts: 5,817	Re: A40c murphy radio Great set and original. It's just a shame that he didn't get a "four minute/minuet" warning Paul as just a little reading around on here or elsewhere would have avoided/reduced the risk. Maybe there should be a banner on the site-If You Are New To Restoration Don't Do This etc! Perhaps he will return for all the advice, a restorer or a sale? Dave

9th May 2018, 12:29 pm	#17
ELVISROY Retired Dormant Member Join Date: May 2018 Location: St. Ives, Cornwall, UK. Posts: 3	Re: A40c murphy radio Hi Mike and all those who replied, i actually put it back on and it stopped smoking but i had radio stations playing last night bit crackly but it was a Bosnia channel im not sure if it was just accumulation of dust that made the smoke, dont want to spend any money on it just like the cabinet but if someone wants to buy it they can Attached Thumbnails

9th May 2018, 12:44 pm	#18
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: A40c murphy radio Brilliant idea to have a new comer warning at the top of the site home page,even if it says do not plug-in. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

30th Sep 2018, 11:04 pm	#20
mister valve Hexode Join Date: Aug 2009 Location: Blackpool, Lancashire, UK. Posts: 311	Re: Murphy A40C radio Shame you're at the other end of the country. If you still have the set, I would have been very interested in buying it. Trouble is I have no transport and it would cost an arm and a leg to get a removal company to get it up here (Blackpool). They are fantastic sets, good performers and well made too, but like all sets of that age, restoration is a must before it is used; otherwise serious and expensive damage can be caused to it. __________________ If you live, the chassis was dead; if you're dead, the chassis was live !!!!