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Murphy Radio Junkshop find.
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April 6, 2017
4:44 pm
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sideband
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I was browsing around a junk  second-hand shop in Beckenham today and came across a Murphy bakelite radio. I was dithering about buying it seeing as I really only concentrate on 30's to 40's radio's and suspect it is early 50's. No idea of model number at this stage as there doesn't seem to be one on the outside. As it was only £20 I decided to rescue it.

I'll take a proper look later but having whipped the bottom plate off, it all looks original and untouched. I thought the design was unusual enough to be 'interesting'.

 

No doubt one of you learned people will tell me the model number without hesitation.....

SAM_1152.JPGImage Enlarger

April 6, 2017
5:13 pm
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Cathovisor
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To know yet to think that one does not know is best; not to know yet to think that one knows will lead to difficulty. Lao Tzu
April 6, 2017
5:16 pm
freya
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Nice find, the A100F has a frame aerial.

Trader 907 for the A100, I have the supplement if you need it for the A100F

April 6, 2017
5:57 pm
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sideband
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Thanks! It's an A100F in that case since it has the frame aerial. Also it just falls into my area of interest being 1948 so doubly pleased at finding this and not a bad price either.

 

Just printed out the service info so now will take it up to the workshop and have a rest from the Perdio Portarama. 

 

Interesting...it uses an autotransformer for the heaters. 

April 6, 2017
11:20 pm
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sideband
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....and a few little probems! The first of which was getting the wavechange knob off. The screw was seized and as it only screws into a Bakelite thread, it had either rusted to the spindle or rust had caused the screw to seize inside the bakelite. It turned out to be the second. WD40 and some heat eventually freed the screw. I was then able to remove the cabinet. Lets just say that mechanically, this will present some challenges! Apart from that, the set seems to have been preserved quite well underneath the dust, fosilised spiders and other long-dead insects. One slightly worrying point is that the voltage selector is in the 200V position. Not knowing the history of the set or where it came from we can only speculate. The set doesn't look like it's seen mains for many, many years. It was bought in the Beckenham area but of course could have come from anywhere. I do know that, right up until the mid 60's, many areas in and around London were still 200V. Hopefully the set was in use in a 200V area. Norbury, Streatham, parts of Croydon and Crystal Palace were all 200V. Beckenham is only a short distance from Crystal Palace so it may also have been 200V.

Anyway having carried out a quick assessment and vacuumed all the dust and dead inhabitants away, the radio seems to be in pretty good condition. None of the waxies have been changed and most of the other components appear original. There is a Radiospares wirewound in there so it's had a repair at some time. All of the rubber wiring is in poor condition and the mains lead is split and frayed. All of that will have to be changed before considering applying mains. There is one electrolytic with white deposits at each end....that's the output valve cathode bypass so that will be changed. The main smoothers actually measure out quite well so they may reform. Otherwise I'll have to restuff. It's got an original set of Mazda valves and I only have one in my stock......hopefully new ones won't be needed.

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General view underneath

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The frayed and broken mains lead

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Perished rubber wiring...this is mains wiring to the switch.

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With the tuning scale removed, the mains transformer

and filter choke can be seen. There is a lot squeezed in.

 

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With a good vacuum out, it doesn't look so bad.

April 7, 2017
12:08 am
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Cathovisor
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As yours is an 'F' version, it won't have the third wire in the mains lead used as an aerial! I don't have any of my supply voltage tables to hand, sadly so cannot confirm if Beckenham was a 200V area in 1950.

I'm afraid Murphy wire of that era is awful: my A104 needed a total rewire because it was all like that. As regards accessibility of course, it could be worse: it could be a McMichael 808...

To know yet to think that one does not know is best; not to know yet to think that one knows will lead to difficulty. Lao Tzu
April 7, 2017
9:17 am
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sideband
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Cathovisor said

As regards accessibility of course, it could be worse: it could be a McMichael 808...  

As I said, this one is going to present some 'challenges'. For example, I need to clean up the volume control spindle (rust) as the on/off operating knob alters the volume rather than just pivoting on the volume spindle. Getting to the nut securing the volume control is relatively easy (slide the on/off knob forward to give clearance). However once the control is free, you can't remove it completely as the back of the pot hits the stud holding the mains input choke.......

 

I note that Murphy state in their service info words to the effect that 'accessibility hasn't been compromised and most parts can be replaced if the instructions are followed.....' They don't tell you how to remove the volume control, only how to access the nut!
 

April 7, 2017
9:39 am
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Is it any wonder Bush's DAC90 hammered it into the ground on sales...? No problems getting at anything on a DAC90 - including a snort of asbestos!

I think the only sets in my collection that're as much of a PITA to deal with as this  are my Ekco A33 and the aforementioned McMichael - for which the Trader's disassembly instructions include tapping the fixing nuts for the handle around with a screwdriver hit with a hammer!

To know yet to think that one does not know is best; not to know yet to think that one knows will lead to difficulty. Lao Tzu
April 7, 2017
9:25 pm
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Katie_Bush
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If it's of any interest, I saw a couple of these radios on eBay last night. One looked a bit worse for wear, but the other appeared quite tidy. Starting prices were decidedly low, so could be worth your having a look at?

If at first you don't succeed, try a new fuse!

April 8, 2017
10:35 am
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Brian Cuff
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Cathovisor said
Trader's disassembly instructions include tapping the fixing nuts for the handle around with a screwdriver hit with a hammer!  

You see, Cathy, there is a need for a hammer in my service kit - just in case I need to get the handle off a McMichael 808!

Cheers

Brian

April 8, 2017
12:10 pm
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Every tool kit needs a hammer, Brian - it's what you use it for that counts!

If someone made a crescent-shaped 2 B.A. spanner, the hammer would not be needed as then it would fit the nut easily. Placing the nut and starting it on the thread; now, that's another matter... nuts_gif

To know yet to think that one does not know is best; not to know yet to think that one knows will lead to difficulty. Lao Tzu
April 8, 2017
9:50 pm
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ntscuser
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Around these parts we call it a "Brumagem Screwdriver" grin_gif

April 8, 2017
10:11 pm
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Katie_Bush
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My granddad always used to call a hammer the Manchester screwdriver, though according to Robbie Coltraine it was an Edinburgh socket set, so I guess it depends a lot upon where you are in the world when you use it!

I could quite well imagine a Mancunian referring to a hammer as a Yorkist nut spinner! - I wonder if Albert Einstein might have called it a "Temporal percussive spatial relocator" - hit for long enough and you'll move it!

If at first you don't succeed, try a new fuse!

April 16, 2017
11:37 pm
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sideband
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Back to the actual restore. It's going to take a little while....no 'quick fix' for this I'm afraid! The rubber wiring is dreadful. Most if not all of it will need to be replaced. Accessibility is difficult in most cases and will require considerable dismantling to get at it. I have managed to extract the volume control. This involved loosening the sub-bracket that holds the mains transformer and mains choke...it was the latter component the prevented removal of the control by virtue of the fact that the securing post of the choke prevented the volume control from being pulled back far enough to clear the volume control bracket. Loosening the transformer bracket enabled me to move the assembly and clear the volume control. 

I'm really not sure if the designer of this set was very clever or should have been sectioned......! It certainly requires thought and methodical working. One thing is dead certain...all the waxies and any other suspect components will be replaced as I go. There is absolutely no way that I will want to remove loads of screws and brackets in order to get to an all but inaccessible capacitor once it's reassembled! 

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Necessary to remove brackets to access wiring

 

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The volume control hits the mounting stud

of the mains filter choke so...

 

js640_SAM_1187.jpgImage Enlarger

...the bracket holding the mains transformer

is loosened so that the volume control can be

removed.

 

I've also removed the speaker which allows better access to the output transformer.

 

js640_SAM_1171.jpgImage Enlarger

See where the tone correction capacitor 

is mounted.

 

...and I haven't even started the rewire yet......!

April 17, 2017
9:59 pm
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sideband
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I've started so I'll finish......

Rewiring has started. I'm also trying to stick to the original colour coded wiring seeing as I now have plenty of different colours. It has been necessary to remove both smoothing caps in order to make enough room to get at everything....just as well as I found more buried components, the audio coupling cap for one. That is virtually impossible to replace without removing the smoothing cap. I've started with the mains wiring (with the exception of a new mains lead at the moment). Voltage selector and mains transformer are done and part of the mains input choke. Also the AC feed to the rectifier. 

js640_SAM_1194.jpgImage Enlarger

Components buried under the smoothing cap.

Top centre just above the 47k resistor is the audio coupling cap. You can now see why it's better to replace these components while other parts are removed.

 

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The rubber insulation has welded itself to adjacent wires. It's all gone hard and falls apart when trying to separate it. All has to be replaced.

 

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Fortunately I have a good supply of various colours.

 

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Here's the first stage around the on/off switch...

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...mains input choke....

 

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...and mains transformer.

Next session will finish off the mains choke and make a start under the chassis and around the output transformer.

April 22, 2017
7:33 pm
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sideband
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More rewiring done and I've made a start replacing the waxies as I go. So far every waxy removed has been very leaky. The coupling cap was measuring around 950K. The remaining waxies will be just as bad. I've also replaced one resistor, a 4.7K HT decoupling resistor which was somewhat distressed and measuring nearer 7K. Other resistors have so far been within spec. The screened lead to the volume control has been disconnected for the moment and some of the heater wiring has been replaced.

 

Pictures show progress.

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Mains transformer rewire complete

 

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Mains input choke wiring 

 

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Mains switch wiring (less mains lead for now)

It's easier to fit a new mains lead when everything else 

is bolted back together.

 

js640_SAM_1215.jpgImage Enlarger

Here I've replaced more wiring, two waxies,

The output valve cathode bypass electrolytic 

(which was open circuit) and the 4.7K HT decoupling

resistor. Only one end connected at the moment, the other

end will connect to the HT decoupling capacitor.

 

js640_SAM_1216.jpgImage Enlarger

Finally, some of the heater wiring has been replaced.

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