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Old 20th Nov 2017, 11:02 pm   #1
Zebra625
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Default Murphy radio, beginner questions. Identified as a U472.

Well, at the weekend we bought our very first vintage radio! It is a Murphy make and looks old (and very beautiful) but other than that we don't know much about it so are hoping for some advice, please.

The attached photos include one with a close up of the dial so you can see all the radio station names written on it, and one taken in darkness with it switched on so you can see the dial lit up.

I have some questions about it which I hope someone will be patient with me and answer, as this is our first foray into owning anything like this.

Q1. How do we find out (or does anyone know from looking at the photos) what model of radio this is, and how old it is?

Q2. Presumably it is a valve radio?

Q3. When we switch it on, the dial immediately lights up and then dims again. Then after a while the light starts to appear again, at first very dim then getting brighter, and the volume gets louder simultaneously. Is this normal, and can someone explain what is technically happening during all this as I'm curious to understand the workings? I'm thinking that the 'getting brighter and louder slowly' is the valves warming up? But I'm not sure about the initial first brightness of the dial.

Q4. Where on earth is the aerial? There is no telescopic aerial or aerial wire of any sort dangling off it, yet the reception is very clear.

Q5. How best do we look after this radio? At the moment we've only listened to it a couple of times maybe for 30 seconds - 1 minute at most and then switched it off because we're unsure whether it is good or bad to have it on for long periods at first.


Many thanks in advance,

Love
Zebra.
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Old 20th Nov 2017, 11:24 pm   #2
Nuvistor
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Default Re: Murphy radio, beginner questions

Have you bought this fully restored and safety checked, if not you have either some work to do or to have done to make it viable?
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Old 20th Nov 2017, 11:27 pm   #3
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Default Re: Murphy radio, beginner questions

Hi Zebra

It looks like a model U472 from 1958.

Yes a valve Radio.

The behaviour of the scale lights is more or less as follows
On switch on the filaments are cold so draw more current so the dial light starts bright then dims as the valves warm up, once HT starts to flow and the radio comes alive this extra current makes the dial light go brighter.

The set has built in aerials but can also use external aerials in poor signal conditions.

If its not been restored there may be a few small cheap parts that need replacement once thats done your can run the set for hours.

Cheers

Mike T
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Old 20th Nov 2017, 11:31 pm   #4
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Default Re: Murphy radio, beginner questions

If it has not been recently serviced or restored, DO NOT TURN IT ON.
If the audio coupling capacitor/s is/are failing you risk destroying the output transformer and or the output valve if they are not replaced.
Read the "stickies" at the top of the radio forum section. They will help and guide you.
Post questions and you will be helped.
We need to know what electrical experience and knowledge you have and if you have any test equipment, eg a multimeter etc.
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Old 20th Nov 2017, 11:32 pm   #5
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Default Re: Murphy radio, beginner questions

Further to Mikes post.
https://www.radiomuseum.org/r/murphy_u472_u_472.html
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Old 20th Nov 2017, 11:57 pm   #6
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Default Re: Murphy radio, beginner questions

If you didn't know the model because the rear cover with the type number on it is missing BE VERY CAREFUL AND DON'T TOUCH ANYTHING INSIDE unless the set is disconnected from the mains (unplugged, not just switched off).

The set has a live chassis (the metal box with the valves etc plugged into it) which is connected directly to the mains supply with a 50/50 chance that it is at 240Vac.

If it's complete with back and knobs it's not inherently dangerous, but any "Live Working" for diagnosis of faults etc needs an extra dose of care and attention compared with a set that is isolated from the mains by a transformer inside!

It's a good looking set- I've got one
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Old 21st Nov 2017, 8:38 am   #7
Zebra625
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Default Re: Murphy radio, beginner questions

Oh dear, I fear I've given you all the impression that we're messing around with a dangerous radio set, and that wasn't my intention at all! The radio came as "good working order" and has a PAT Test sticker attached to the label which says it was tested 6/5/17. It is all in one piece, no bits missing. Don't worry, we wouldn't dream of switching something on if we didn't think it was safe!

I shall reply to everyone's comments individually in a further reply, but at the moment I'm getting ready for work.

Love,
Zebra
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Old 21st Nov 2017, 10:23 am   #8
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Default Re: Murphy radio, beginner questions. Identified as a U472.

Let me repeat.

It's not advisable to use this set until you've established that the audio coupling capacitor has been replaced. It's not so much a matter of safety, but one of concern for the set's well being.

We see many threads on here which go something like this:-

"I found an old set and plugged it in. It worked fine for a few minute/hours/days and then there was a bang/smoke came out and the set stopped working. What is wrong with it?"

Often the set is now beyond economic repair and all for the sake of not replacing a capacitor costing a few pence.
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Old 21st Nov 2017, 10:45 am   #9
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Default Re: Murphy radio, beginner questions. Identified as a U472.

PAT stickers will not prevent the damage caused by a faulty audio coupling capacitor.
I never mentioned safety issues, just wanted to prevent you wrecking the radio by using it in ignorance and unrestored.
Sorry if you became alarmed. I've got my hat and coat and left.
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Old 21st Nov 2017, 11:43 am   #10
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Default Re: Murphy radio, beginner questions. Identified as a U472.

Is a PAT acceptable for an AC/DC live chassis radio?
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Old 21st Nov 2017, 1:06 pm   #11
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Default Re: Murphy radio, beginner questions. Identified as a U472.

The OP should be aware that the PAT test is just an electrical safety test. If this is to be used as an ornament then clean it up and leave it as is. If it is to be used regularly, I would suggest that the radio is used for increasing long periods say 2 mins, 5 mins, 10 mins, 30 mins and let it charge itself in. If there are any burning smells/overheating after c.2 minutes do not use it until serviced. Do not leave it on an unattended. Do not attempt to touch the internals whether on or off. If there is any doubt, a Member of this Forum near to you might check it over.
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Old 21st Nov 2017, 1:16 pm   #12
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Default Re: Murphy radio, beginner questions. Identified as a U472.

That's a moot point!

A visual inspection of the state of the set's casing and mains lead and plug (including inside the plug and the fuse rating) is part of PAT and would be very acceptable / applicable for such a set. Insulation resistance checks too.

The set in as original condition would likely pass a typical PAT check. (Whether a "typical" PAT check actually confirms safety is another matter entirely.)

What it won't do is meet current requirements for safety for new equipment, but that doesn't necessarily mean it's unsafe to use.
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Old 21st Nov 2017, 6:18 pm   #13
Zebra625
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Default Re: Murphy radio, beginner questions. Identified as a U472.

Thank you all for your replies, much appreciated. Apologies if my reply this morning didn't come across right, I was rushing to post so I could get off to work without being late!

We don't know whether the audio coupling capacitor has been replaced or not; therefore until we find out we will not switch the radio on.


Love,
Zebra
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Old 21st Nov 2017, 8:11 pm   #14
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Default Re: Murphy radio, beginner questions. Identified as a U472.

You will need to get the radio chassis out of the case to see whether the capacitor everyone is referring to has been replaced. You can get a service sheet by clicking on the link at the top right of the page.

Once you have it out of the case photograph the underside of the chassis and post the photograph on here. Have you ever done any soldering? (Amusingly the spell checker on my computer wanted to change soldering to slobbering!)
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Old 22nd Nov 2017, 12:01 am   #15
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Default Re: Murphy radio, beginner questions. Identified as a U472.

Well that's not a bad description of inexpert soldering!
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Old 22nd Nov 2017, 12:11 am   #16
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Default Re: Murphy radio, beginner questions. Identified as a U472.

As has been said, PAT testing does not imply the set is working properly. Too much emphasis is placed on PAT testing....it's like a buzz word similar to 'digital' (if it's digital it must be good). It may prove that the set is safe to plug in and you are unlikely to get a shock from it but it is very far from confirming that the radio is working properly.
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Old 22nd Nov 2017, 12:25 am   #17
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Default Re: Murphy radio, beginner questions. Identified as a U472.

Take the advice Zebra. As the very experienced Moderator Station X said, there may be risks around you're level of understanding-even more if you don't know what you don't know if you see what I mean. This Forum was originally set up by enthusiasts who had [generally] developed or already had a basic knowledge base before seeking help. Their entire interest was primarily vintage restoration. The advent of retro enthusiasm now brings in people who are very enthusiastic but at risk of being naive and often with a different motivation eg based soley on the "look" of the item-itself an important consideration but not really the same thing. It's a bit like saying-"I like vintage cars or my vehicle is a bit dodgy where do I start? Some basic research is the answer. Take care out there!

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