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Old 11th Dec 2020, 10:54 pm   #1
Gabe001
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Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 1,612
Default Another Murphy A362 restoration

This is for Ken (kentode), as promised. Thanks for the tips

I acquired this set from Facebook marketplace and it had been in the same family since it was first bought. I had been after the Murphy a362 for a while, but the ones on eBay were going for too high a price.

When it arrived in the post there was a rattle in the case. Fearing the worst I unscrewed the back panel to inspect the damage. Luckily it was only the FM aerial that had come loose; it didn't cause any damage to other components. Apart from that, it looked in good condition cosmetically. The bubble wrap had imprinted on the bakelite and the front grille needed a clean. The bakelite polished up nicely with brasso and the grille cleaned up well too and this took no time at all.

Removing the chassis was incredibly fiddly. The chassis cannot come out because the dial pointer is infront of the grille, so this requires either careful manouvering through the slit or removing the pointer from the cord entirely. The speaker wires are the shortest I've ever seen!

I think there definitely was some animosity between the service engineers at Murphy and the product designers, because nothing could have prepared me for the layers upon layers of hunts capacitors in the strangest and most inaccessible of places! Ignoring these for now, I replaced the grid coupling capacitor and applied power gently via a lamp limiter. It works immediately on all bands, without the grief I got from the KB MR10, except for a mild hum on FM only. Suspecting a leaky FM "upside down" electrolytic capacitor, this was the next to go, and it sorted the hum.

The smoothing electrolytic reformed nicely. I probably could have left it. However, for no specific reason at all other than the cap being over 60 years old, I replaced it with two 2*47uf caps mounted on a tag strip. The original smoothing cap contained two 50uf capacitors rated 350v.

After replacing the last waxy and, after some advice from this forum, fitting type y caps on the signal and earth line (this set is a live chassis with signal earth tied to mains earth) it was time to replace the Hunts caps. I was dreading this.

One by one, slowly, using diagrams for reference and sometimes having to remove one to access another, they were gradually replaced. It was a time consuming and delicate process. 0.04uf were replaced by 0.047uf and so forth.

The finishing touches included a clean of the inside of the case, a clean of the valves, servisol to the waveband switch and valve bases, lubricating oil to the pulleys and tightening of the grub screw holding the dial tuning gang (I'm not sure if this is the proper name for the part) to the spindle of the tuning capacitor (it was loose). Also the set got a new bulb and the FM aerial was put back into its position and fixed with a few dabs of glue. Kitchen foil was used to replace the perished original . The speaker had a small tear which was also patched up. Finally, I replaced the original mains cable with a modern 3 core cable and fitted a new plug with a 1A fuse.

Finally, it was time to reassemble the set, plug in the FM aerial and give it a proper test.

So how does it compare to my kitchen set, the KB MR10?

This is a video of me tuning the FM band of the Murphy using its internal aerial
https://youtu.be/aaeAB_QBNZc

Compare this to the KB using a 1.5m wire as an aerial (in the same spot in the house at the same time of day)
https://youtu.be/m-pTOAJEU4c

The KB has an internal ferrite rod aerial so there's no contest on AM. The FM on the Murphy is better, but not by much. I can get smooth FM which I cannot get on the KB and some weaker stations like radio X sound better on the Murphy. The BBC stations are strong on both sets.

Overall very happy with how this set turned out and how it performs, and it looks as good as I expected. It was a difficult set to work on though.

Hope someone finds this useful

Gabriel
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Last edited by Gabe001; 11th Dec 2020 at 11:06 pm.
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Old 12th Dec 2020, 9:30 am   #2
Kentode
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Default Re: Another Murphy A362 restoration

Well done Gabriel! The case always looks brown in photos, but they've actually maroon.

I also used kitchen foil to overlap the FM aerial as it was cracked at the corners.

Whatever radio you restore next, it won't be as hard as this one was.
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Old 26th Dec 2020, 4:14 pm   #3
Xyience
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Default Re: Another Murphy A362 restoration

Great write up Gabriel. I found it useful.

The first valve radio I purchased, way back in August, was an A362. The owner was a radio enthusiast with other projects on the go - he didn't want to tackle this Murphy due to the 'offensive layout on the underneath of the chassis'. Ho Hum - meant nothing to me at the time; I just wanted a nice, cheap, semi-working radio with glowing tubes inside.
The A362 is on a high shelf, waiting for my abilities to reach a point where we can do battle.
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Old 26th Dec 2020, 6:28 pm   #4
Gabe001
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Default Re: Another Murphy A362 restoration

Thank you. Its a good performer, but yes the layout is indeed offensive.

Having said that, I've got a philetta on the bench (aka kitchen table) and it's worse!
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