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Old 1st Apr 2024, 12:49 pm   #1
David Simpson
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Default Ekco u76

Controversy - maybe, Ruffle a few old feathers - maybe.
Kindly given this set by a VR Chum. Thanks to "Ellie" for PDF's of documentation. As with "Trader" sheets & Ekco's own Circuit diagrams for the A22 I worked on last year - slight difference in component ID's.
The set was in very good nick, and all the valves tested fine for their age. The bakelite cabinet polished up a dream. I like the lovely serpentine sides.
Folk might remember my past views on AC/DC Sets. First thing I did was remove the controversial "two wire flex" & its modern 3 pin plug. Fitted new 3 core cable & took E to chassis via a 0.1 p/e cap. Also fitted fuses in the V5 feed & heater dropper feed from the mains switch. Replaced associated perished v/r wiring.
Powered up on Variac via an Isol. T/F, and also from my DC PSU. Fine on all Bands using just the internal loop aerials.
But, and its a big But - would not use or recommend use on Domestic Mains, for 21st Century safety reasons. Likewise - to earth the chassis for PAT purposes - merely trips the domestic RCD. And so it jolly well should !

Regards, David
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Old 1st Apr 2024, 1:59 pm   #2
David Simpson
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Default Re: Ekco u76

More pictures.
Forgot to mention - changed R21 & R23 b/t/s resistors & tidied up the heater dropper.
Talking of Ekco A22's & U76's - "Radio Radio" tells us that they both cost £14 back in 1947. Nowadays an A22 is worth hundreds and the U76 a few tens of quid. Incidentally, no other bakelite set in R-R has such nice big bakelite knobs set into such lovely sides. My all-time favourite bakelite set has always been the Ferranti 145, but this comes a close second.
Just a final point - ordinary table top sets mostly take about 150 to 170mA from the mains. Many times, when removing 3 pin plugs - what do I find - a heffing 13A BS1362 fuse ! 1A ones are hard to find but I wonder if there are still 0.5A ones available in that 1" size these days ? I've use both in the past in BS1363 type plugs.

Regards, David
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Old 1st Apr 2024, 4:49 pm   #3
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Default Re: Ekco u76

Feathers duly ruffled!

If the set's in good condition with no accessible live parts it's no more dangerous to use now than it was 75 years ago. Less so if it's fed from an RCD plug or the household supply is RCD protected.

Not sure about that earth to chassis via 0.1uF either- sounds like a recipe for letting in mains borne interference.
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Old 1st Apr 2024, 5:31 pm   #4
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Default Re: Ekco u76

I also can't see the point of a 3 core cable where the earth connection effectively isn't doing anything.

It would actually have passed a PAT test unmodified, but will now fail because it's been modified and needs to comply with current regs - it's lost its grandfather rights.
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Old 1st Apr 2024, 8:53 pm   #5
David Simpson
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Default Re: Ekco u76

In the U76, Neutral floats at 6.3V(pilot light) & a 33ohm resistor above chassis potential after the on/off switch. Also, Ekco themselves have taken in their Earth connection via a 0.1uF capacitor.
Looking in through the U76's wide-slotted back panel - - plenty of room for little Jonny or little Jenny to poke through a desert spoon or something even larger metallic & make contact with the heater dropper or the HT smoothing choke which are within an inch's distance ! No way safe in either the 20th century or the 21st. U76's and their AC/DC kin are in no way "totally enclosed" or "double insulated" by any stretch of the imagination.
Yep - nice to look at, and no doubt the prize possession of some VR folk who have restored them. Nothing wrong with those same folk powering them up on 240V DC or via a mains Isol. T/F. Openly flogging one from a shop, as "working" - not a chance, legally, without a PAT Cert. Ask a BVWS auctioneer to flog one with a 3 pin plug on it - - snipperty snip! If I pass this U76 on to someone else - I'll point out the missing 3 pin plug - that'll be their choice to fit. And, I'll point out the label info. In fact, in the past, I've never flogged an AC/DC set - just given them away to folk as a "display item". Hopefully to be placed on a shelf 6' off the floor.

Regards, David
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Old 2nd Apr 2024, 10:16 am   #6
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Default Re: Ekco u76

I completely agree that live chassis radios should always be sold to the general public as static display items. It's then up to them should they decide to power them up. I would never recommend operating a live chassis set when there are young children around.

I know removing the mains plug has become standard practice, but I'm not convinced that it has any legal effect.
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Old 2nd Apr 2024, 11:23 am   #7
David Simpson
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Default Re: Ekco u76

Just thought I'd post a picture of Ekco's Circuit Diagram.
Although it's raised long discussed safety questions, actually it was just an AFD Jape(as some might have suspected). No malice or disrespect to any VR enthusiast. Just happened that I'd finished working on the nice looking set & had placed it on my wee display shelf - on the 1st April.
Now returning to re-purposing an AVO 1388B, nearly finished.

Regards, David

Last edited by Cobaltblue; 2nd Apr 2024 at 8:12 pm. Reason: Rule B8
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Old 2nd Apr 2024, 8:07 pm   #8
Ed_Dinning
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Default Re: Ekco u76

Hi folks, a 0.1uF cap is a bit large as an "earth isolating" cap and may give problems with the leakage breaker.
Typical "equivalent " cap values on modern equipment suggest a Y cap of about 4n7 would be more suitable.
There would then be the problem of PAT testin g and "modifications"

Ed
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Old 2nd Apr 2024, 9:39 pm   #9
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Default Re: Ekco u76

I agree with Paul. It seems a bit strange to have an earth wire down to the chassis via a 0.1 cap. The only thing that would make sense to me would be to not use the chassis as a neutral return, then you could connect the earth to it. It would then provide protection against earth fault.
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Old 2nd Apr 2024, 11:50 pm   #10
David Simpson
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Default Re: Ekco u76

Removing the Pilot Light & it's 33ohm shunt, and connecting switched Neutral & the incoming Earth straight to chassis makes everything tickerty-boo PAT-wise and the mains RCD doesn't drop out. In fact - the ideal remedy, safety-wise. Yep, slightly alters the spread of heater voltages via the dropper, and the voltage presented to V5's anode, but the set works fine. I tried it. However, no pilot light & no back light behind the glass tuning dial(not that there was much anyway). So where to safely source a voltage for a wee PL Bulb whose wee edison screw retainer is firmly clipped to the front metal earthed structure? Thought of a diddy ES 110V or 240V Neon with a safety multiplier, but thought it unsafe & too much faffing about.
So put everything back together as per original CD. Seeing as it worked fine from my DC HT PSU, or from an Isol.T/F - which is what I recommend for AC/DC sets anyway. If this set ever goes to someone else, who is a VR buff, then they can chose to retain the Earth connection or make their own alterations.
This set's redeeming features are it's lovely bakelite good looks & it's signal reception quality from the rear mounted loop aerials.

Regards, David

PS. What started out as a bit of "Jock-urality", April 1st-wise, from the North of Scotland - now a drawing out thread. But hey, not to worry.
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Old 3rd Apr 2024, 10:31 am   #11
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Default Re: Ekco u76

Quote:
Originally Posted by David Simpson View Post

PS. What started out as a bit of "Jock-urality", April 1st-wise, from the North of Scotland - now a drawing out thread. But hey, not to worry.
Maybe it doesn't apply N of the border, but looking at the time of posting #1, 49 minutes after midday, by tradition the joke's on you
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Old 3rd Apr 2024, 10:59 am   #12
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Default Re: Ekco u76

There have actually been semi-serious proposals for England and Scotland to use different time zones.

Back on topic now please.
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Old 3rd Apr 2024, 11:52 am   #13
David Simpson
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Default Re: Ekco u76

Yep. I agree Paul.
One final note, which no doubt many AC/DC buffs already ken - these sets take a fair bit longer to "warm up", and subsequently to tune in to a desired station. One thing I observed with this set, whilst slowly turning up the Variac, at about 200V - stations can indeed be picked up, all be it at lower volume. But hey-leave it a bit longer & max volume doesn't drop off that much. Our mains, being from an 11KV/480V split phase T/F about 70m away - gives a jolly good 240V, so dropper tapping duly sat at that. So hats off to Ekco for making such a versatile wee set.
I'll throw this in, although it's O/T and thoroughly debated many times Forum-wise - - our 16mm sq. u/g cable from the T/F is "straight concentric"(just L & N - no Earth conductor) so the whole caboodle from the T/F is PME - with the N conductor also connected to the Earth Terminal on the incoming "Cut-Out"( supplier's main fuse holder). So in fact, U76 circuitry-wise, N is E !
I guess Paul, now's the time to close the thread.

Regards, David
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