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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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27th Feb 2017, 3:18 pm | #1 |
Hexode
Join Date: Oct 2015
Location: Sunderland, Tyne and Wear, UK.
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Ekco A22 capacitor value
Hi all,
I’m currently restoring an Ekco A22 and seem to have an inconsistency in one of the capacitor values. The a.f. coupling capacitor to the EBL31 (Trader C24, manufacturer’s C30) is stated to be 0.05uF but my set has a 0.005uF component installed. Has anyone else come across the lower value in their own sets? There aren’t any obvious signs that it has been replaced in the past. I realise it probably doesn’t matter a great deal but I’m re-stuffing the waxies on this set and probably won’t be able to change it again later on. Cheers Liam |
27th Feb 2017, 4:41 pm | #2 |
Rest in Peace
Join Date: Mar 2011
Location: Basildon, Essex, UK.
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Re: Ekco A22 capacitor value
Sounds like human error when the set was assembled.
Mike |
27th Feb 2017, 5:08 pm | #3 |
Pentode
Join Date: Jan 2013
Location: Nottingham, Notts. UK.
Posts: 228
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Re: Ekco A22 capacitor value
I've come across values different to that stated on the schematic for a set on a few occasions but not by a factor of 10.
In this case though the reduction in value won't have any significant effect so I'm guessing it could be cost cutting, shortage of the correct value or human error as Mike suggests. |
27th Feb 2017, 5:13 pm | #4 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,766
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Re: Ekco A22 capacitor value
I've restored three and as found, they were all .05µF per the original Ekco Datasheet.
If you're stuffing the waxies, I guess you'll be stuffing the upright cathode bypass cap (25µF 25V). No great chore. By far the nicest of the round Ekcos and the easiest to restore, with most components on the tag-board on outside of the rim of the chassis. Good luck with the restoration Liam.
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David. BVWS Member. G-QRP Club member 1339. |
27th Feb 2017, 5:16 pm | #5 |
Guest
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Re: Ekco A22 capacitor value
Having had a look at the trader sheet I wold plump for the higher value, makes more sense for audio.
Last edited by Guest; 27th Feb 2017 at 5:17 pm. Reason: spelling |
27th Feb 2017, 5:42 pm | #6 |
Hexode
Join Date: Oct 2015
Location: Sunderland, Tyne and Wear, UK.
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Re: Ekco A22 capacitor value
Thanks all. I'll go for 0.05. Might have to find a narrower type to fit inside the tube. I agree the A22 is a nice set to work on. The round construction is very practical and not just for show. Fingers crossed the EBL31 is ok!
Cheers Liam |
27th Feb 2017, 5:43 pm | #7 |
Pentode
Join Date: Jan 2013
Location: Nottingham, Notts. UK.
Posts: 228
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Re: Ekco A22 capacitor value
I would say that, considering the high input impedance of the output valve (many MOhms), going for the higher or lower value will have no significant effect on the audio quality. In either case the low frequency roll-off is going to be well below 20Hz.
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27th Feb 2017, 6:18 pm | #8 | ||
Guest
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Re: Ekco A22 capacitor value
Quote:
Quote:
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27th Feb 2017, 6:41 pm | #9 |
Heptode
Join Date: May 2011
Location: Letchworth Garden City, Hertfordshire, UK.
Posts: 693
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Re: Ekco A22 capacitor value
Looks like the C30 I removed from mine is 0.05uF. Hard to see a decimal point, despite cleaning all the goo off.
Go carefully with component replacement. On my A22, found that a lot of internal fittings suffered from metal fatigue. I wasn't being too rough, but a few of the tag strip eyelets turned from closed O shape into open U shapes when de-soldering old component legs. Also, some of the P clips holding the wiring loom around the outside of the chassis split in two when unscrewed. Good Luck! SR |
27th Feb 2017, 6:48 pm | #10 |
Rest in Peace
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Location: Harlaxton, Lincolnshire, UK.
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Re: Ekco A22 capacitor value
The manufacturers manual confirms it is indeed 0.05uF.
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27th Feb 2017, 7:32 pm | #11 | |||
Pentode
Join Date: Jan 2013
Location: Nottingham, Notts. UK.
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Re: Ekco A22 capacitor value
Quote:
Anyway using the formula 1/2pi*R*C for the -3dB roll off frequency and substituting 1M (volume pot) for R gives: 32Hz for a value of 0.005uF for C24 and 3.2Hz for a value of 0.05uF. Both should be acceptable in this radio I would have thought. |
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27th Feb 2017, 8:10 pm | #12 |
Guest
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Re: Ekco A22 capacitor value
I used an online time constant calculator and did the reciprocal, near enough IF the calculator or my inputs where 10X out, which seems to be the case here. OOPS
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27th Feb 2017, 9:16 pm | #13 |
Rest in Peace
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Re: Ekco A22 capacitor value
I do not think the fittings were damaged by fatique. Much more likely to be season cracking.
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5th Mar 2017, 6:05 pm | #14 |
Hexode
Join Date: Oct 2015
Location: Sunderland, Tyne and Wear, UK.
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Re: Ekco A22 capacitor value
A quick followup question on the A22. Does anyone know how to remove the switched volume pot on this set?
The switch on mine measures o/c and I'd like to try opening it. Do I need to unscrew the fastening around the spindle shown in the attached photo? I don't really want to force it till I know for certain. |
5th Mar 2017, 6:18 pm | #15 |
Dekatron
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Location: Chesterfield, Derbyshire, UK.
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Re: Ekco A22 capacitor value
Yes that is the fixing nut , try a bit of heat on it if it is stuck , Mick.
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5th Mar 2017, 7:06 pm | #16 |
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Re: Ekco A22 capacitor value
OC measured mains switches often respond to (with the thing plugged in) a few cycles of on/off. This burns off the oxide layer.
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5th Mar 2017, 7:55 pm | #17 |
Hexode
Join Date: Sep 2010
Location: Stourbridge, West Midlands, UK.
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Re: Ekco A22 capacitor value
I love my A22, but wish the audio sounded better, it sounds very flat.
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6th Mar 2017, 4:33 am | #18 |
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Re: Ekco A22 capacitor value
What? You haven't got surROUND sound?
Lack of top, no treble, could be low HT if you have checked everything else. |
6th Mar 2017, 11:45 am | #19 | |
Hexode
Join Date: Oct 2015
Location: Sunderland, Tyne and Wear, UK.
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Re: Ekco A22 capacitor value
Quote:
Liam |
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6th Mar 2017, 3:08 pm | #20 |
Guest
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Re: Ekco A22 capacitor value
Do it with the valves out (saves the poor heaters), leave the pilot lamp in for indication.
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