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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 4th May 2018, 8:57 pm   #1
Boater Sam
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Default Portable Murphy with attitude repaired.

Bought, with real money, another Ekco A385 transistor portable. Produced from September 1959.
I've had a few of these in the past, they have all worked well and just needed cleaning.

The two 6v batteries are bit of a pain as they are no longer widely available but there is plenty of room for a double stack of AAs or even good old HP11s, C types to younger members. Draw is only around 20mA at reasonable volume so they last well.

The first difficulty is getting the set out of its leather zip up case, they are a very close fit and the zip gets in the way. This one has a well worn case, the zip is partially detached.

Once out, it looks not bad, a bit grubby but the case is not cracked, the knobs are on, dials legible. Slow motion tuning spindle works.
Opening the 2 parts of the case reveals a clean interior, no batteries or spill damage but the top moulding seems loose, there is a screw missing from one end of the top chassis plate and the other is loose. Has this been played with? No obvious signs of repairs.
Many nasty Hunts 0.04uf capacitors, several 50uf electrolytics from the same stable
( were they made in a stable, is that why they are so bad? ) and a couple of Plessey red and blacks.
Speaker is good. One knob is cracked on the spindle moulding, superglue and a metal collar fixed that, the other has a small crack across the face.

On with the split power supply and oh dear, a box full of whistles, Medium Wave finds stations but the whistle kills them, they are quiet but selectivity seems good. Long Wave is a bit better, louder, but the whistle either side of the station is horrendous.
Obviously there is bad instability somewhere. The coil and IF transformer cores are sealed, the trimmers likewise seem undisturbed. Switches are noisy, but clean up OK.

Now these radios are a serviceman's nightmare to get access to all the components. The old Fairchild transistors are scattered around 3 sides of the multi piece chassis in no logical order as are the rest of the components with wires traversing to and fro around the piano key switches where more components are buried.
The battery boxes are stapled around a "U" shaped aluminium bar that slots into both sides of the chassis and has to come out for access by flexing it after removing the speaker.

A quick test of the audio stages by disconnecting the capacitor on the volume control shows these stages to be stable and working fine, so its instability in transistors 1 to 4.
Trader sheet 1585 covers this set. Now transistors 1 &2 are on the top near the switch bank, next to #5! Then #3 & #4 are on the side plate. Its unusual as there is a mixer and a separate oscillator transistor.

Ok, so what's causing the instablity? It will be those Hunts plastic caps for sure. The Plesseys will go too. And there are a few Suflex nasties buried in the switch bank. Change C47, C48, C44, C37,C53 ,C13, C24 one at a time. It gets a bit louder, Long Wave is better but the whistle is still there. Beginning to look like a bad one to sort.
I would have liked to change C42 and C34 but they are very difficult to get to and testing the removed capacitors reveals that though the values are elevated, signifying that they are slightly leaky, they should be OK in a transistor set with low voltages.

Thinking cap on, check the remaining electrolytics as they are decouplers and emitter bypasses, they are fine despite being Hunts. Read the instructions (well, circuit diagram) seems a good idea.
Now this reveals that there are components listed that are not fitted! Particularly C51 which is a 0.04uf capacitor decoupling the negative rail to the first 4 transistors. There is a 50uf already on this rail but the sheet says that C51 was also fitted to later sets.
So this is an early one, why did Murphy have to put an extra decoupler on that rail with later production? They did nothing if not necessary, never wasted money.

I fitted one and...........Whistles Gone! Volume back up to what I would expect, loads of stations on Medium Wave, job done.

Problem solved, a quick check on the tuning being in track, reassemble and clean and there is another old set back in working order.

Anyone want a few old Hunts and Plesseys, pre-used?
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Old 5th May 2018, 6:22 am   #2
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Default Re: Portable Ekco with attitude repaired.

Hi Sam
Nice write up and useful hints on the repair of an issue with instability.
I could find no information on this radio in the Radio Museum.
It would be nice to see some photos of it in there and the service information if you have it.

If you can't add them to the Radio Museum yourself, you can email them to me if you like and I will propose it as a new model.

Cheers
Mike
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Old 5th May 2018, 7:08 am   #3
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Default Re: Portable Ekco with attitude repaired.

My take on it is this...Murphy would not have sold an unstable set! It's very likely that when the set was new and those decouplers were in first-class condition, it wasn't unstable since the capacitors at that time were able to bypass any RF that crept into the I.F stages. As the set aged, the ESR went up (maybe only after a few years) causing instability or maybe some sets were only marginal, bordering on instability and after only a short while were going unstable. This resulted in Murphy adding the .04 as an additional RF filter in later production to avoid nuisance failures.
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Old 5th May 2018, 9:26 am   #4
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Default Re: Portable Ekco with attitude repaired.

I've not come across an Ekco-Murphy before....Murphy B385?

Lawrence.
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Old 5th May 2018, 10:09 am   #5
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Default Re: Portable Ekco with attitude repaired.

I thought that the Murphy here might be the one associated with the well known laws of inanimate objects.....

http://www.murphys-laws.com/murphy/murphy-laws.html
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Old 5th May 2018, 10:21 am   #6
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Default Re: Portable Ekco with attitude repaired.

Murphy B385 had a zip outer case and a 0.04uf capacitor (C51) supply decoupler on the schematic, and two batteries.

Lawrence.
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Old 5th May 2018, 10:35 am   #7
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Default Re: Portable Ekco with attitude repaired.

Yes, that fits. Unlike the carrying case, which isn't leather - I think they called it "neohide" - and shrinks. When I first met these in the late '60s getting them in or out of the case wasn't nearly such a struggle.

Paul
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Old 5th May 2018, 12:24 pm   #8
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Default Re: Portable Murphy with attitude repaired.

Well shoot me. Of course its a Murphy.
I started to enter a thread about a nasty Ekco, changed my mind and forgot to edit. Blame it on age related lunacy. Or the hot weather, finally. Another fail in cut and paste.
Got someone's attention anyway.
Perhaps the mods would change the title for me. Please.
I've got my coat and hat.

The instability probably arises from changes over time in the wound components but as the cores are tiny and locked. I consider it prudent to leave them alone.
Murphy obviously realised that the stability of the front end was marginal hence the revision and fitting of C51 cap. The trader sheet is from 1963, 4 years after the launch in 1959 so the change must have occurred sometime before 1963.
I will have a look at the Murphy works sheet and see if the change is noted there too.

I never thought about the case shrinking, its more likely than the set expanding. Same result, I'll leave it off I think.
If Paul remembers these from the late '60s they must of been in production for a long time. The later ones have the Mullard range of transistors.
They must be one of the last radios constructed on a chassis and tag boards, pcb construction was well advanced in the '60s.
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Old 5th May 2018, 1:37 pm   #9
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Default Re: Portable Murphy with attitude repaired.

There is no date on the manufacturer's sheets as to when the modification was made, but it must have been quite early in production.
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Old 5th May 2018, 5:34 pm   #10
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Default Re: Portable Murphy with attitude repaired.

Quote:
Originally Posted by Boater Sam View Post
If Paul remembers these from the late '60s they must of been in production for a long time...
I met two or three of them in 1968/9, but they weren't by any means new: it's just that the cases weren't nearly so tight as they are now! According to Radio! Radio!, which generally seems right on such matters, the very similar B485 was released in February '61, so B385 production will have ended before then.
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Old 7th May 2018, 10:49 pm   #11
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Default Re: Portable Murphy with attitude repaired.

Nice repair and enjoyable write-up, Sam, well done.
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Old 9th Aug 2018, 5:21 pm   #12
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Default Re: Portable Murphy with attitude repaired.

I had a BUSH TR106 that howled like a werewolf. That turned out to be a (completely) open circuit 100uF de- coupling capacitor in the IF section.

Well done Sam. I wish I saw more vintage transistor sets.
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Old 13th Aug 2018, 5:13 pm   #13
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Default Re: Portable Murphy with attitude repaired.

Hi Sam
Your quote is on the right tract I seem to remember that Hunts used a old RAF Building in the village of Eaton on tern . Located between Telford and Mkt Drayton . Some young ladies that I know worked there in the late 1950's. Might have been a bit better than a stable but not much.
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Old 14th Aug 2018, 9:19 am   #14
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Default Re: Portable Murphy with attitude repaired.

A good and interesting write up. Well done for finding that fault.
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Old 14th Aug 2018, 9:41 am   #15
Boater Sam
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Default Re: Portable Murphy with attitude repaired.

There are those that consider that I have not found the fault at all!

But as it now conforms to the circuit diagram and works properly I think I will accept that Murphy knew that there was a possible sensitivity to oscillation and that they solved the manufacturing fault for me.
Sam.
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