Ferguson 382U Firefly not playing ball - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

Simon Gittins · 10th Apr 2019, 8:12 pm

Not the cause of radio silence but have you used a Class X capacitor for that orange one in the 1st picture going from switched live to chassis? If the replacement isn't rated for use across the mains it could go bang!

You could just leave it out whilst testing. The capacitors to the sockets should be Class Y but again they don't need changing until you have the set working.

PJL · 10th Apr 2019, 8:53 pm

Unfortunately, the pictures are still too difficult to follow, not helped by you leaving the old parts in place and snipping one end!

You should be using capacitors that are rated for at least 250V and preferably 400V. I am not sure about the disc ceramics you have used but there seem to be some grey sleeved ones and I remember those being 63V?

I suspect the original image files you are using are better resolution and detail is being lost by the attachment. Maybe you could PM me the originals?

Peter

el gringo · 11th Apr 2019, 8:53 am

Hi Simon/Peter,

Thanks for looking, just checked and both of the orange ones are > 250V rated and the grey ones are apparently marked "500v.

( happy to send images min PMs, dies anyone know how to do this? )

Pete

Station X · 11th Apr 2019, 9:58 am

Images cannot be attached to PM's. You'll need to use email.

jonnybear · 11th Apr 2019, 10:08 am

Quote:

Originally Posted by el gringo

Thanks for looking, just checked and both of the orange ones are > 250V rated and the grey ones are apparently marked "500v.

Hi Pete
The voltage marked on the capacitors ie 250v is a DC rating, If a capacitor is used in AC circuit or across the OP transformer this voltage needs to be trebled at lest, to be on the safe side.
John

Simon Gittins · 11th Apr 2019, 10:21 am

If the capacitor I mentioned in post 41 is rated at 250V DC then it's not suitable for use across the mains.

General information on capacitor replacement:
https://www.vintage-radio.net/forum/...ad.php?t=18962

Information on Class X and Class Y capacitors:
https://vintage-radio.net/forum/showthread.php?t=56159

I wonder whether the DSO that you have could be used to pin down the fault to a particular stage. I'm not familiar with DSOs but if you post details of the one you have someone may be able to advise.

Re the pictures; four overlapping ones of the chassis may give better results.

ms660 · 11th Apr 2019, 10:39 am

I would replace with a suitable type or remove the replacement mains bypass capacitor shown in the photo PDQ before it explodes, I would also replace the Hunts 0.02uF that's shown in the photo, it's the coupling capacitor to the audio amplifier, they are prone to going electrically leaky, if it goes leaky the bias voltage on the grid can be seriously reduced, that can lead to increased distortion.

Lawrence

Herald1360 · 11th Apr 2019, 10:43 am

Which could be the least of the problems it causes!

el gringo · 11th Apr 2019, 10:45 am

Ah okay point taken re cap DC voltage rating!

Very interesting posts on X and Y rated capacitors! Looks like I'm gonna be replacing those for sure..

Will attach four overlapping pics too..

ms660 · 11th Apr 2019, 10:50 am

Quote:

Originally Posted by Herald1360

Which could be the least of the problems it causes!

I don't get that....

Lawrence.

Nuvistor · 11th Apr 2019, 10:59 am

I took it to mean that the increased Ia through the valve could damage the valve, output TX etc.

el gringo · 11th Apr 2019, 11:22 am

5 overlapping images ( they seem to be fairly heavily reduced! )

Pete

ms660 · 11th Apr 2019, 11:28 am

Quote:

Originally Posted by Nuvistor

I took it to mean that the increased Ia through the valve could damage the valve, output TX etc.

If that's what he was meaning (we don't know for sure yet) he would be wrong.

Lawrence.

Nuvistor · 11th Apr 2019, 11:51 am

Hi Lawrence,
Just checked the photos and circuit, is the 0.02 you refer to connected between the triode grid and V/C C51 on the maker's circuit?

ms660 · 11th Apr 2019, 11:52 am

It was indeed, that's the fella (the capacitor).

Lawrence.

PJL · 11th Apr 2019, 2:16 pm

I can see C22 (0.005) that is the grey sleeved small capacitor. Are you sure this is 250V or higher?
Where is C21 (0.005)? It seems to be missing.

PJL · 11th Apr 2019, 2:44 pm

And C47 hidden in the waveband switch is a Hunts and will need replacing. This is only used for FM so ignore this for now, just work with MW.

el gringo · 11th Apr 2019, 3:10 pm

Thanks PJL - was about to ask about C47 too ( just seen it lurking between the two wafers ) I'm not at all sure about the AC rating for that small grey cap? it's printed value appears to be "500v". For C21, I've got a longish thin red cap going from pin 1 of V2 to ground, is that it?

Quote:

Originally Posted by jonnybear

The voltage marked on the capacitors ie 250v is a DC rating, If a capacitor is used in AC circuit or across the OP transformer this voltage needs to be trebled at lest, to be on the safe side.

Thanks Jonny - I really only ever worked on low voltage stuff when I was an Engineer, so this is def kinda new to me!

Pete

PJL · 11th Apr 2019, 3:27 pm

OK, so C21 is an original ceramic capacitor? Should be OK although they do sometimes break in two if you move them about too much. It is not possible to see Pin 1 in your picture so can you confirm both C21 and C22 (critical for RF) are connected to pin 1.

Just to be sure we are on the same page, we are working off trader 1299.

el gringo · 11th Apr 2019, 3:43 pm

Hi yes it is the original. Both C21 and C22 ( the replacement grey one ) are connected to pin 1 of V2.

Pete

10th Apr 2019, 8:12 pm	#41
Simon Gittins Heptode Join Date: Jan 2006 Location: Cornwall, UK. Posts: 506	Re: Ferguson 382U Firefly not playing ball Not the cause of radio silence but have you used a Class X capacitor for that orange one in the 1st picture going from switched live to chassis? If the replacement isn't rated for use across the mains it could go bang! You could just leave it out whilst testing. The capacitors to the sockets should be Class Y but again they don't need changing until you have the set working.

10th Apr 2019, 8:53 pm	#42
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Ferguson 382U Firefly not playing ball Unfortunately, the pictures are still too difficult to follow, not helped by you leaving the old parts in place and snipping one end! You should be using capacitors that are rated for at least 250V and preferably 400V. I am not sure about the disc ceramics you have used but there seem to be some grey sleeved ones and I remember those being 63V? I suspect the original image files you are using are better resolution and detail is being lost by the attachment. Maybe you could PM me the originals? Peter

11th Apr 2019, 8:53 am	#43
el gringo Tetrode Join Date: Mar 2019 Location: Surrey, UK. Posts: 77	Re: Ferguson 382U Firefly not playing ball Hi Simon/Peter, Thanks for looking, just checked and both of the orange ones are > 250V rated and the grey ones are apparently marked "500v. ( happy to send images min PMs, dies anyone know how to do this? ) Pete

11th Apr 2019, 9:58 am	#44
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,286	Re: Ferguson 382U Firefly not playing ball Images cannot be attached to PM's. You'll need to use email. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

11th Apr 2019, 10:21 am	#46
Simon Gittins Heptode Join Date: Jan 2006 Location: Cornwall, UK. Posts: 506	Re: Ferguson 382U Firefly not playing ball If the capacitor I mentioned in post 41 is rated at 250V DC then it's not suitable for use across the mains. General information on capacitor replacement: https://www.vintage-radio.net/forum/...ad.php?t=18962 Information on Class X and Class Y capacitors: https://vintage-radio.net/forum/showthread.php?t=56159 I wonder whether the DSO that you have could be used to pin down the fault to a particular stage. I'm not familiar with DSOs but if you post details of the one you have someone may be able to advise. Re the pictures; four overlapping ones of the chassis may give better results.

11th Apr 2019, 10:39 am	#47
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Ferguson 382U Firefly not playing ball I would replace with a suitable type or remove the replacement mains bypass capacitor shown in the photo PDQ before it explodes, I would also replace the Hunts 0.02uF that's shown in the photo, it's the coupling capacitor to the audio amplifier, they are prone to going electrically leaky, if it goes leaky the bias voltage on the grid can be seriously reduced, that can lead to increased distortion. Lawrence Last edited by ms660; 11th Apr 2019 at 10:44 am. Reason: addition

11th Apr 2019, 10:43 am	#48
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Ferguson 382U Firefly not playing ball Which could be the least of the problems it causes! __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

11th Apr 2019, 10:45 am	#49
el gringo Tetrode Join Date: Mar 2019 Location: Surrey, UK. Posts: 77	Re: Ferguson 382U Firefly not playing ball Ah okay point taken re cap DC voltage rating! Very interesting posts on X and Y rated capacitors! Looks like I'm gonna be replacing those for sure.. Will attach four overlapping pics too..

11th Apr 2019, 10:59 am	#51
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: Ferguson 382U Firefly not playing ball I took it to mean that the increased Ia through the valve could damage the valve, output TX etc. __________________ Frank

11th Apr 2019, 11:22 am	#52
el gringo Tetrode Join Date: Mar 2019 Location: Surrey, UK. Posts: 77	Re: Ferguson 382U Firefly not playing ball 5 overlapping images ( they seem to be fairly heavily reduced! ) Pete Attached Thumbnails

11th Apr 2019, 11:51 am	#54
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: Ferguson 382U Firefly not playing ball Hi Lawrence, Just checked the photos and circuit, is the 0.02 you refer to connected between the triode grid and V/C C51 on the maker's circuit? __________________ Frank

11th Apr 2019, 11:52 am	#55
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Ferguson 382U Firefly not playing ball It was indeed, that's the fella (the capacitor). Lawrence.

11th Apr 2019, 2:16 pm	#56
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Ferguson 382U Firefly not playing ball I can see C22 (0.005) that is the grey sleeved small capacitor. Are you sure this is 250V or higher? Where is C21 (0.005)? It seems to be missing.

11th Apr 2019, 2:44 pm	#57
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Ferguson 382U Firefly not playing ball And C47 hidden in the waveband switch is a Hunts and will need replacing. This is only used for FM so ignore this for now, just work with MW.

11th Apr 2019, 3:27 pm	#59
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Ferguson 382U Firefly not playing ball OK, so C21 is an original ceramic capacitor? Should be OK although they do sometimes break in two if you move them about too much. It is not possible to see Pin 1 in your picture so can you confirm both C21 and C22 (critical for RF) are connected to pin 1. Just to be sure we are on the same page, we are working off trader 1299.

11th Apr 2019, 3:43 pm	#60
el gringo Tetrode Join Date: Mar 2019 Location: Surrey, UK. Posts: 77	Re: Ferguson 382U Firefly not playing ball Hi yes it is the original. Both C21 and C22 ( the replacement grey one ) are connected to pin 1 of V2. Pete