UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Closed Thread
 
Thread Tools
Old 27th Feb 2017, 3:18 pm   #1
Voxophone
Hexode
 
Voxophone's Avatar
 
Join Date: Oct 2015
Location: Sunderland, Tyne and Wear, UK.
Posts: 340
Default 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
Voxophone is offline  
Old 27th Feb 2017, 4:41 pm   #2
crackle
Rest in Peace
 
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
Default Re: Ekco A22 capacitor value

Sounds like human error when the set was assembled.

Mike
crackle is offline  
Old 27th Feb 2017, 5:08 pm   #3
DigitalNoMore
Pentode
 
Join Date: Jan 2013
Location: Nottingham, Notts. UK.
Posts: 228
Default 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.
DigitalNoMore is offline  
Old 27th Feb 2017, 5:13 pm   #4
David G4EBT
Dekatron
 
David G4EBT's Avatar
 
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
Default 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.
__________________
David.
BVWS Member.
G-QRP Club member 1339.
David G4EBT is offline  
Old 27th Feb 2017, 5:16 pm   #5
Guest
Guest
 
Posts: n/a
Default 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
 
Old 27th Feb 2017, 5:42 pm   #6
Voxophone
Hexode
 
Voxophone's Avatar
 
Join Date: Oct 2015
Location: Sunderland, Tyne and Wear, UK.
Posts: 340
Default 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
Voxophone is offline  
Old 27th Feb 2017, 5:43 pm   #7
DigitalNoMore
Pentode
 
Join Date: Jan 2013
Location: Nottingham, Notts. UK.
Posts: 228
Default 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.
DigitalNoMore is offline  
Old 27th Feb 2017, 6:18 pm   #8
Guest
Guest
 
Posts: n/a
Default Re: Ekco A22 capacitor value

Quote:
I would say that, considering the high input impedance of the output valve (many MOhms)
There is the 1M volume pot to ground (ground ish anyway) 0.05 is 20Hz (not noticable) 0.005 200Hz (most noticable).
Quote:
Might have to find a narrower type to fit inside the tube
It has a low voltage across it, a slim 63V job will do admirably.
 
Old 27th Feb 2017, 6:41 pm   #9
Stuart R
Heptode
 
Stuart R's Avatar
 
Join Date: May 2011
Location: Letchworth Garden City, Hertfordshire, UK.
Posts: 690
Default 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
Stuart R is offline  
Old 27th Feb 2017, 6:48 pm   #10
ukcol
Rest in Peace
 
ukcol's Avatar
 
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,944
Default Re: Ekco A22 capacitor value

The manufacturers manual confirms it is indeed 0.05uF.
Attached Thumbnails
Click image for larger version

Name:	A22audio.jpg
Views:	105
Size:	48.4 KB
ID:	138275  
ukcol is offline  
Old 27th Feb 2017, 7:32 pm   #11
DigitalNoMore
Pentode
 
Join Date: Jan 2013
Location: Nottingham, Notts. UK.
Posts: 228
Default Re: Ekco A22 capacitor value

Quote:
Originally Posted by merlinmaxwell View Post
Quote:
I would say that, considering the high input impedance of the output valve (many MOhms)
There is the 1M volume pot to ground (ground ish anyway) 0.05 is 20Hz (not noticable) 0.005 200Hz (most noticable).
Quote:
Might have to find a narrower type to fit inside the tube
It has a low voltage across it, a slim 63V job will do admirably.
That'll teach me to look at a schematic before posting! The 1M pot will indeed affect the low frequency roll off.

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.
DigitalNoMore is offline  
Old 27th Feb 2017, 8:10 pm   #12
Guest
Guest
 
Posts: n/a
Default 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
 
Old 27th Feb 2017, 9:16 pm   #13
TrevorG3VLF
Rest in Peace
 
TrevorG3VLF's Avatar
 
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
Default Re: Ekco A22 capacitor value

I do not think the fittings were damaged by fatique. Much more likely to be season cracking.
TrevorG3VLF is offline  
Old 5th Mar 2017, 6:05 pm   #14
Voxophone
Hexode
 
Voxophone's Avatar
 
Join Date: Oct 2015
Location: Sunderland, Tyne and Wear, UK.
Posts: 340
Default 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.
Attached Thumbnails
Click image for larger version

Name:	DSC_0363_01.JPG
Views:	119
Size:	149.7 KB
ID:	138651  
Voxophone is offline  
Old 5th Mar 2017, 6:18 pm   #15
vinrads
Dekatron
 
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,737
Default Re: Ekco A22 capacitor value

Yes that is the fixing nut , try a bit of heat on it if it is stuck , Mick.
vinrads is online now  
Old 5th Mar 2017, 7:06 pm   #16
Guest
Guest
 
Posts: n/a
Default 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.
 
Old 5th Mar 2017, 7:55 pm   #17
crusher19860138
Hexode
 
Join Date: Sep 2010
Location: Stourbridge, West Midlands, UK.
Posts: 434
Default Re: Ekco A22 capacitor value

I love my A22, but wish the audio sounded better, it sounds very flat.
crusher19860138 is offline  
Old 6th Mar 2017, 4:33 am   #18
Boater Sam
Banned
 
Join Date: Dec 2013
Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
Posts: 3,897
Default 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.
Boater Sam is offline  
Old 6th Mar 2017, 11:45 am   #19
Voxophone
Hexode
 
Voxophone's Avatar
 
Join Date: Oct 2015
Location: Sunderland, Tyne and Wear, UK.
Posts: 340
Default Re: Ekco A22 capacitor value

Quote:
Originally Posted by merlinmaxwell View Post
OC measured mains switches often respond to (with the thing plugged in) a few cycles of on/off. This burns off the oxide layer.
Thanks. I'll give it a go and see how it works out. I'm pretty close to powering up now. Just need a couple more caps and the top connector re-glueing on the EBL31.

Liam
Voxophone is offline  
Old 6th Mar 2017, 3:08 pm   #20
Guest
Guest
 
Posts: n/a
Default Re: Ekco A22 capacitor value

Do it with the valves out (saves the poor heaters), leave the pilot lamp in for indication.
 
Closed Thread

Thread Tools



All times are GMT +1. The time now is 9:48 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.