Ferguson 356A. Resistor Identification - UK Vintage Radio Repair and Restoration Discussion Forum

CrackBangPop · 3rd May 2018, 10:07 pm

Hi,

New to the site, first post!

First of all I'm new to all this, and don't have much electrical/radio knowledge but I'm fine with replacing a resitor or two.

I have a Ferguson 356a, not worth much and not a great radio I know, but I'd still like to get it running. Anyway it was tested and working upon receiving it, then set aside for a while.

I decided to give the a case clean so removed the back and immediately noticed a resistor with a broken lead, a 500ohm resistor, green, black, brown. But when I check the service sheet for the radio, there is no 500ohm resistor listed and wondered if the sheet is wrong or maybe somebody put in the wrong resistor and that's why it has a broken lead! Although it all looks original and untouched.

It runs from pin 9 of valve 2 (EBF80) according to the service sheet. I'm not 100% confident in myself following the circuit diagram so I'm wondering if anyone here could identify what it's actually meant to be.

image attached and can provide more if needed, I've read the rules and see I'm not allowed to post service sheets, I hope the cropped circiut diagram is ok.

Thanks in advance,

Marc.

Boater Sam · 3rd May 2018, 10:36 pm

Reckon it's C28, a capacitor.
The rounded ends are the give away.

'LIVEWIRE?' · 3rd May 2018, 10:43 pm

Are you sure that isn't a capacitor? (C28 is connected between pin 9, which is earthed as you can see from the diagram, and the secondary of the I.F. Transformer. C28 is part of the filter circuit following the detector. The green, black, & brown bands would then indicate 500pf. This assumes you haven't actually measured the component at 500 ohms. (Boater Sam has just put it more succinctly!)

Nuvistor · 3rd May 2018, 10:43 pm

Yes I agree with you Sam, it appears to be C28.

dazzlevision · 3rd May 2018, 10:54 pm

It’s a Dubilier capacitor. See photo 4 in post 1 here: https://www.vintage-radio.net/forum/...ad.php?t=98964

CrackBangPop · 3rd May 2018, 11:40 pm

Oh wow, well that explains my confusion. I wasn't aware of such capacitors! I did think it was a little unusual how the ends are rounded but the stripes like a resistor threw me off.

I still have a lot to learn..

Thanks all for the replies!

HamishBoxer · 4th May 2018, 10:05 am

possibly .01 or 001uF cap.

ms660 · 4th May 2018, 10:34 am

Doesn't look like C28 to me, looks more like C23 (500pF) Check out pin 2 of the EBF80 to the IF transformer, pin 2 is g1, hence C23 on t'other end....The IF amp is a reflex job (IF/AF)

Lawrence.

Station X · 4th May 2018, 10:39 am

Agreed. It's connected to pin 9 which has a strap to the chassis and you can see a broken wire on what is presumably L6. The value is 500pF.

dazzlevision · 4th May 2018, 10:55 am

Agreed, C23. The green, black, brown colour code is for 500pF.

HamishBoxer · 4th May 2018, 11:53 am

Of course Green = 5!

CrackBangPop · 4th May 2018, 8:05 pm

Thanks again, so we're settling on C23 then. I did think it was goiNg to the 1st IF (L5/L6) before I posted since the broken lead is on what the service sheet says is 1st IF. So when it was first said that it may be C28 and going to second IF, I thought great, I know even less than I thought I did!

Also do I need any specific type of cap to replace this with? I'm mainly seeing poly or radial silver mica 500pf caps for sale, the silver mica seem easier to get hold off.

ms660 · 5th May 2018, 9:15 am

Silvered mica will be ok to use.

The connections to the EBF80 can easily be confused when tracing out because there are three transformer windings connected to it, in this case g1 is IF in and AF in.

Lawrence.

dazzlevision · 5th May 2018, 9:45 am

A close tolerance (usually 1%) Silvered Mica type may well prove expensive (if you have to buy one). A much cheaper axial leaded Polyester film 10% 250Vdc working type will be fine, as it is just a decoupling capacitor on the AGC line.

G8UWM-MildMartin · 5th May 2018, 12:33 pm

470pF may be easier to find. Ceramic would also be OK.

CrackBangPop · 5th May 2018, 3:11 pm

Ah that's good to know thanks, so whatever I can find cheapest that's the cloest value.

I was also planning on changing the cap on the output transformer, it's a 0.002uf 1000v waxy paper cap but I can't seem to find any, all I can find at 1000v are 0.0022uf, would that be ok?

Also, could anyone recommend any books or links on the basics of how valve radios work? There's lots of information on the internet but I can't seem to find anything that just goes over all the basic parts, what they do, how and why etc.

Thanks again,

Marc.

ms660 · 5th May 2018, 3:35 pm

0.0022uf is fine, no problem.

What does what.....have a look through this lot:

https://www.vintage-radio.com/repair...ion/index.html

Lawrence.

3rd May 2018, 10:07 pm	#1
CrackBangPop Retired Dormant Member Join Date: May 2018 Location: North Yorkshire, UK. Posts: 4	Ferguson 356A. Resistor Identification Hi, New to the site, first post! First of all I'm new to all this, and don't have much electrical/radio knowledge but I'm fine with replacing a resitor or two. I have a Ferguson 356a, not worth much and not a great radio I know, but I'd still like to get it running. Anyway it was tested and working upon receiving it, then set aside for a while. I decided to give the a case clean so removed the back and immediately noticed a resistor with a broken lead, a 500ohm resistor, green, black, brown. But when I check the service sheet for the radio, there is no 500ohm resistor listed and wondered if the sheet is wrong or maybe somebody put in the wrong resistor and that's why it has a broken lead! Although it all looks original and untouched. It runs from pin 9 of valve 2 (EBF80) according to the service sheet. I'm not 100% confident in myself following the circuit diagram so I'm wondering if anyone here could identify what it's actually meant to be. image attached and can provide more if needed, I've read the rules and see I'm not allowed to post service sheets, I hope the cropped circiut diagram is ok. Thanks in advance, Marc. Attached Thumbnails

3rd May 2018, 10:36 pm	#2
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Ferguson 356A.Resistor Identification Reckon it's C28, a capacitor. The rounded ends are the give away.

3rd May 2018, 10:43 pm	#3
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Ferguson 356A. Resistor Identification Are you sure that isn't a capacitor? (C28 is connected between pin 9, which is earthed as you can see from the diagram, and the secondary of the I.F. Transformer. C28 is part of the filter circuit following the detector. The green, black, & brown bands would then indicate 500pf. This assumes you haven't actually measured the component at 500 ohms. (Boater Sam has just put it more succinctly!)

3rd May 2018, 10:43 pm	#4
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: Ferguson 356A. Resistor Identification Yes I agree with you Sam, it appears to be C28. __________________ Frank

3rd May 2018, 10:54 pm	#5
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,621	Re: Ferguson 356A. Resistor Identification It’s a Dubilier capacitor. See photo 4 in post 1 here: https://www.vintage-radio.net/forum/...ad.php?t=98964

3rd May 2018, 11:40 pm	#6
CrackBangPop Retired Dormant Member Join Date: May 2018 Location: North Yorkshire, UK. Posts: 4	Re: Ferguson 356A. Resistor Identification Oh wow, well that explains my confusion. I wasn't aware of such capacitors! I did think it was a little unusual how the ends are rounded but the stripes like a resistor threw me off. I still have a lot to learn.. Thanks all for the replies!

4th May 2018, 10:05 am	#7
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: Ferguson 356A. Resistor Identification possibly .01 or 001uF cap. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

4th May 2018, 10:34 am	#8
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Ferguson 356A. Resistor Identification Doesn't look like C28 to me, looks more like C23 (500pF) Check out pin 2 of the EBF80 to the IF transformer, pin 2 is g1, hence C23 on t'other end....The IF amp is a reflex job (IF/AF) Lawrence. Last edited by ms660; 4th May 2018 at 10:44 am. Reason: explanation

4th May 2018, 10:39 am	#9
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Ferguson 356A. Resistor Identification Agreed. It's connected to pin 9 which has a strap to the chassis and you can see a broken wire on what is presumably L6. The value is 500pF. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

4th May 2018, 10:55 am	#10
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,621	Re: Ferguson 356A. Resistor Identification Agreed, C23. The green, black, brown colour code is for 500pF.

4th May 2018, 11:53 am	#11
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: Ferguson 356A. Resistor Identification Of course Green = 5! __________________ G8JET BVWS Archivist and Member V.M.A.R.S

4th May 2018, 8:05 pm	#12
CrackBangPop Retired Dormant Member Join Date: May 2018 Location: North Yorkshire, UK. Posts: 4	Re: Ferguson 356A. Resistor Identification Thanks again, so we're settling on C23 then. I did think it was goiNg to the 1st IF (L5/L6) before I posted since the broken lead is on what the service sheet says is 1st IF. So when it was first said that it may be C28 and going to second IF, I thought great, I know even less than I thought I did! Also do I need any specific type of cap to replace this with? I'm mainly seeing poly or radial silver mica 500pf caps for sale, the silver mica seem easier to get hold off.

5th May 2018, 9:15 am	#13
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Ferguson 356A. Resistor Identification Silvered mica will be ok to use. The connections to the EBF80 can easily be confused when tracing out because there are three transformer windings connected to it, in this case g1 is IF in and AF in. Lawrence.

5th May 2018, 9:45 am	#14
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,621	Re: Ferguson 356A. Resistor Identification A close tolerance (usually 1%) Silvered Mica type may well prove expensive (if you have to buy one). A much cheaper axial leaded Polyester film 10% 250Vdc working type will be fine, as it is just a decoupling capacitor on the AGC line.

5th May 2018, 12:33 pm	#15
G8UWM-MildMartin Heptode Join Date: Jan 2004 Location: Stockport, Greater Manchester, UK. Posts: 827	Re: Ferguson 356A. Resistor Identification 470pF may be easier to find. Ceramic would also be OK.

5th May 2018, 3:11 pm	#16
CrackBangPop Retired Dormant Member Join Date: May 2018 Location: North Yorkshire, UK. Posts: 4	Re: Ferguson 356A. Resistor Identification Ah that's good to know thanks, so whatever I can find cheapest that's the cloest value. I was also planning on changing the cap on the output transformer, it's a 0.002uf 1000v waxy paper cap but I can't seem to find any, all I can find at 1000v are 0.0022uf, would that be ok? Also, could anyone recommend any books or links on the basics of how valve radios work? There's lots of information on the internet but I can't seem to find anything that just goes over all the basic parts, what they do, how and why etc. Thanks again, Marc.

5th May 2018, 3:35 pm	#17
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Ferguson 356A. Resistor Identification 0.0022uf is fine, no problem. What does what.....have a look through this lot: https://www.vintage-radio.com/repair...ion/index.html Lawrence.