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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 12th Apr 2006, 11:25 am   #1
David G4EBT
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Default Ekco A22 - restoration hints and tips?

My son has hankered after a round Ekco and has managed to acquire an A22, which he hasn't yet received. Cosmeticaly it's in good shape, and the person who's selling it him says it doesn't work, (why am I not surprised?!), but there's a faint hum from the speaker, so I guess that where there's life, there's hope!

The dial (which I assume is perspex) has a crack. Does anyone know if this is just a "window" over the actual dial, or are the dial markings printed on it? Is it just a flat circular piece of perspex, or is it moulded to a shape?

I seem to recall that at an NEC fair a gentleman called Clive Simpson supplied replacement dials, but I've no details of where he is or if he still does this.

I know it's a rather daft thing to say when I haven't even seen the set and started any diagnostic work, (rather like a doctor being expected to diagnose and ailment without the patient being present), but are there any stock faults particular to this set to look out for, other than the general range of faults which arise on sets of this vintage (leaky caps, electrolytics, valve failure etc).

I've printed off the "Trader Sheet" from the BVWS CD (Thanks again Paul), and the circuit looks fairly conventional, albeit the circular chassis is rather novel.

Any hints and tips would be greatly appreciated.

Thanks for reading.

David,
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Old 12th Apr 2006, 3:44 pm   #2
Paul_RK
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Default Re: Ekco A22 - restoration hints and tips?

Hello David,

It's a while since either of my A22s last came out of its case, but as I recall the tuning scale is flat or very nearly so, and I'm pretty sure (unfortunately) that the markings are printed directly on the rear of it.

No special electronic problems that I can think of: the circuit is indeed a pretty standard short superhet, and the arrangement of most of the minor parts around the outside of the circular chassis makes access and replacement agreeably easy. One of my sets had a failed output transformer on arrival, but I couldn't say whether it's a fault to which they're particularly prone at all. Of the valves, the EBL31 is a little unusual, but was used in quite a few other models as well - several Pyes if memory serves - and shouldn't be especially hard to come by: fortunately it's unloved by the audiophile contingent so far as I'm aware

Good luck with the set... I'm afraid I can't help on a likely source of replacement dials, but someone may well know something.

Paul
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Old 12th Apr 2006, 6:17 pm   #3
sparkie
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Default Re: Ekco A22 - restoration hints and tips?

Chap with the repro dials is Clive Mason, and he lives in Sedgley, West Midlands. He's a BVWS member, so could be contactable through the society, I don't I'm afraid have his phone no, although he may be in the last BVWS members list.

These dials can shrink, and I've seen them go 'dished' (concave) all around the rim of the speaker - never quite worked out why some do this and some don't. Steve
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Old 12th Apr 2006, 7:52 pm   #4
Hoveradio
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Default Re: Ekco A22 - restoration hints and tips?

Hi,Check out this link to Clive Mason.You can contact him via the web page.
http://www.acd-systems.co.uk/valveaudiorepairs.com/
Regards John.
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Old 12th Apr 2006, 9:17 pm   #5
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Default Re: Ekco A22 - restoration hints and tips?

Hi David
I have both black and brown versions of the A22. If I remember right (all my radios are packed away at the moment) the black one has a perspex dial, as Paul says they are flat and printed/painted on the back.
The brown one was given to me some time ago- the dial is definitely celluloid on this particular one and had shrunk/dished considerably (also the black and brown ones have different colour scales). Though a bit scruffy, it hadn't seen any repairs yet still worked well. Probably still does!
Trevor
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Old 13th Apr 2006, 2:43 pm   #6
Panrock
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Default Re: Ekco A22 - restoration hints and tips?

These A22s are the best-performing round Ekcos. Dials commonly show signs of the backing pain lifting. Don't be tempted to try to repair it with similar paint, or you'll probably see the repaired areas as blotches when the dial light shines through.

The rubber wiring on these sets is a particular safety hazard and should be thoroughly checked. The red in particular is often perished and dangerous - this can carry a high voltage.

Steve
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Old 14th Apr 2006, 1:46 pm   #7
David G4EBT
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Default Ekco A22 Valve line-up (output valve)?

Me again,

Thanks for all the helpful advice re my earlier post seeking tips on restoring the A22 which my son has now acquired. Apart from a new mains tranformer having been bodged in, it otherwise seems to have not been got at, but needs a new dial cord, bulb, dial and speaker grille.

Luckily, Clive Mason is able to supply new dials and one's on its way to me.

I've given the set a "test drive" (via a lamp "surge limitter" of course!), and it does work, (albeit some hum needs sorting out).

One oddity is that whereas the valve line-up on the trader sheet shows an EBL31 for the ouput stage, the one fitted is nothing like an EBL31. It has a metalised coating, and maddeningly, the markings have chipped off.

Whereas the EBL31 as I recall is quite a large tall valve, the one fitted is the same size as the ECH35 and EF39. The valvholder and connections all look original, so I don't think anyone's modded the set to fit a different (cheaper?) valve. I may be wrong, but don't think the EBL31 has a direct equivalent.

So, does anyone know if Ekco changed the output valve at some stage please? (The rest of the line-up is as per the trader sheet - ECH35, EF39, AZ31.

The original transformer had a 5v tapping for the 6.3V scale-lamp, rather than using 6.3V. The replacement tranny doesn't. Any idea why only 5V for the scale lamp? (IE to under-run the lamp, or give a dimmer glow or whatever. It seems a needless complication - there must be a reason!).

Many thanks in advance for any thoughts.

David.
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Old 14th Apr 2006, 5:28 pm   #8
Aerodyne
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Default Re: Ekco A22 Valve line-up (output valve)?

On my circuit the 5V winding powers the heaters of the rectifier, the 6.3V winding powers the receiving valve heaters plus the dial lamps.
I think you are correct in that the EBL31 has no direct equivalent - certainly none I know of - so perhaps the wrong bottle has been fitted by someone who may also have altered the lamps supplies?
-Tony
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Old 14th Apr 2006, 10:57 pm   #9
Hoveradio
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Default Re: Ekco A22 Valve line-up (output valve)?

Hi David,Glad to hear that you have had success with the dial from Clive Mason.
EBL31 valves are certainly larger than ef39's etc.They do have a top cap and the ones I have seen have a red coating on the lower part of the valve.Maybe you could post a picture of the valve that is fitted.It's likely that someone on the forum could identify it for you.
The AZ31 rectifier should be fed with a separate 4V winding off the transformer.This is connected to the h.t. line so be aware if you are going to measure it.If 5V is being supplied then you will have to change the rectifier for an appropriate 5V valve.
Regards John.
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Old 14th Apr 2006, 11:20 pm   #10
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Default Re: Ekco A22 Valve line-up (output valve)?

While there are no octal direct equivalents of an EBL31, the side contact EBL1 and the B7 pin PDD2 are very close electrically, so perhaps one of these is fitted via an octal adaptor or changed base on the chassis. During the late 1940s and early 1950s shortages of valves sometimes caused repairers to fit close electrical equivalents - if I remember rightly an EBL1 isn't much bigger than an EF39...
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Old 15th Apr 2006, 12:11 pm   #11
David G4EBT
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Talking Re: Ekco A22 Valve line-up (output valve)?

John, (Hoveradio) wrote:

>EBL31 valves are certainly larger than ef39's etc.They do have a top cap >and the ones I have seen have a red coating on the lower part of the valve.

Yes, that's as I guessed.

>Maybe you could post a picture of the valve that is fitted.It's likely that >someone on the forum could identify it for you.

It's so scruffy that I don't think it would add anything. There are some faint markings ??R55 then 10E/11401. It has the Mil ^ marking too, so I guess it's a CV valve, but the CV equiv of the EBL31 is listed only as CV2926. Funny thing is that the set does work, after a fashion.

Commonsense must rule over frugality, and a replacement EBL31 must beckon!

>The AZ31 rectifier should be fed with a separate 4V winding off the >transformer.This is connected to the h.t. line so be aware if you are going >to measure it.

True - I'm to young to die, and too old for nasty jolts!

The AZ31 is indeed fed from a separate 4V, albeit the transformer isn't the original drop through one. My earlier query re the dial-light is that the Trader Sheet says the 6.3V winding for the other valves is tapped so as to provide 5V to the 6.3V 0.3A dial lamp.

That seemed a puzzling thing to do and a needless complexity, but I guess they must have had their reasons. IE, to under-run the dial light to either dim it or prolong its life? Surley a resistor would have done the same task easier?
Just puzzled - no big deal.

Does conventional wisdom indicate that it's best to routinely replace ALL paper caps, or just certain ones (ie, those carrying the highest voltages? I guess there are mixed views - some say if it ain't broke don't fix it - others may say why wait for the big bang.

Views will obviously differ if it's a commercial complete restoration, or simply to add to one's own collection. (I use the term "commercial" loosely, meaning that money changes hands, rather than that there are rich pickings to be made from honest toil in this game!!). Look upon it as a "callling".

Right, I'll now try to re-string the drive cord. Should be fun.

Thanks for all the help and advice guys.

David
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