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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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10th Dec 2022, 5:08 pm | #1 |
Nonode
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,384
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Barker 534
Hi folks, I've just completed restoration of a Barker 534 that I got at RWB. Not the most sophisticated beast, but I like it and, best of all, it was cheap! It seems rarer than the ubiquitous Barker 88 albeit the 534 has a single Class A 6V6 output valve as opposed to the push-pull pair in the 88. I couldn't find a service sheet for the radio anywhere so I drew out the circuit freehand along with the valve electrode measurements, trimmer identifications and tuning cord diagram. See attached PDF. The radio appeared to be unmolested (just how I like 'em) except for fitment of a brown and blue twin flex. I like my radios earthed so I replaced it with a 3-core mains lead. I had a look at the valves and it was a mixture of Marconi and other octals: U50, 6V6GT, DH63, KTW63, 6K8GT. I'm guessing it probably started out with the other types rather than Marconi. I tested them all and rejected the U50 which was low emission and fitted a decent 5Y3G. All the other valves tested nigh-on 100% so I left them in. I nearly rejected the 6V6GT since I was getting fluctuating readings on the VCM163 until I realised the last valve I'd tested was a magic eye and, after removing the anode load resistor from the VCM163, I hadn't tightened down the shorting strip properly on the anode link terminals . Next I set about reforming the smoothers. All reformed satisfactorily except for the 8uF reservoir which started to reform then went o/c. The other (16uF) cap in the same can was fine so I simply added a tag strip below decks and soldered in a new 10uF 450v radial. The 25uF cathode decoupler on the 6V6GT wouldn't reform so I replaced it. The 0.01uF grid coupler on the 6V6GT was showing a tiny amount of leakage on the Avometer so I replaced it as a precaution. The 0.05uF dc blocker on the tone control was very leaky so I replaced it along with the 0.001uF 6V6GT anode filter cap which tested OK on the Avometer but whose failure could have destroyed the output transformer. The resistors that I tested all remained within 20% so I left them alone. Once I powered up everything worked and the valve electrode readings were normal. Next I tackled the broken tuning cord. Having cursed for a couple of hours I finally worked out the best way to tackle it so I included that in the attached PDF. The scale now read spot on and the sensitivity was excellent so I left the alignment alone. The cabinet is reasonably presentable so I will probably leave as-is. Photo to follow once I get the chassis back in. Jerry
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10th Dec 2022, 9:23 pm | #2 |
Octode
Join Date: Nov 2003
Location: Bath, Somerset, UK.
Posts: 1,805
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Re: Barker 534
That is a nicely proportioned chassis, Jerry. I rather prefer that squarer profile. Too many chassis have a narrower aspect that leaves one feeling as though one is working through a letterbox. There is plenty of space to get around everything.
Neil
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preserving the recent past, for the distant future. |
11th Dec 2022, 2:53 pm | #3 |
Nonode
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,384
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Re: Barker 534
Thanks Neil - I know what you mean and it makes a pleasant change not having to do keyhole surgery on a set and getting burnt fingers as a reward..... A couple of images attached. Jerry
P.S. Mods - if Paul wishes to add my hand-drawn service sheet to the library then feel free! Last edited by cathoderay57; 11th Dec 2022 at 3:01 pm. |
12th Dec 2022, 9:55 am | #4 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,763
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Re: Barker 534
Hmm ! that dial looks like an Etronic not sure about the spelling ,could that be just a badge name. Mick
Last edited by vinrads; 12th Dec 2022 at 10:18 am. |
12th Dec 2022, 10:54 am | #5 |
Heptode
Join Date: Jan 2006
Location: Cornwall, UK.
Posts: 506
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Re: Barker 534
It does look like the Etronic RA640 with left and right swapped:
https://www.radiomuseum.org/r/etronic_ra640.html |
12th Dec 2022, 2:39 pm | #6 |
Nonode
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,384
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Re: Barker 534
Good spot. The circuits are very similar indeed, even down to most of the component values. No magic eye or IF trap on mine though, and on mine the tone control returns to chassis as opposed to the HT line. Wish I'd spotted it - would have saved time drawing out the circuit...... The most useful thing I've picked up is that an indirectly heated rectifier is used, leading to a significantly higher HT. So I'll probably replace the 5Y3G with a 5Z4G. Cheers, Jerry
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12th Dec 2022, 7:59 pm | #7 |
Heptode
Join Date: Apr 2003
Location: Newton Abbot, Devon, UK.
Posts: 761
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Re: Barker 534
It's quite a handsome beast, isn't it? I wonder what it cost when new, and how pleased the original owner was with it?
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