RA17 gone bang - UK Vintage Radio Repair and Restoration Discussion Forum

lightning · 27th Apr 2022, 2:20 pm

l turned on my Racal RA17 last week and after a few minutes working normally there was a fairly loud bang from inside the cabinet followed by a quantity of smoke.

Short of sabotage by the Russians, what should l be looking for? l took the top cover off but everything is inside metal cans, all you can see is the valves really.

The radio is now dead. l assume it's blown a fuse somewhere, it's gone back into the spare room in disgrace along with the dusty "that looks a good idea" jogging machine and cheap electric bike that won't charge.

vosperd · 27th Apr 2022, 2:36 pm

The HT smoothing capacitor C198 and C206 is good candidate. Mounted horizontally under the chassis. If not there is a good chance there will be some other visible evidence.
Don m5aky

paulsherwin · 27th Apr 2022, 2:46 pm

If the smoother has gone bang it will have blown the end out - it should be very obvious. There may be gunk all over the place too.

HamishBoxer · 27th Apr 2022, 3:08 pm

Mains suppression cap across the mains input ?

Radio Wrangler · 27th Apr 2022, 3:13 pm

I wouldn't delay. The guck from exploded or leaky capacitors can be corrosive. It'll be a smaller job done sooner rather than later.

David

lightning · 27th Apr 2022, 3:56 pm

Thank you for the advice.

l'll get on to it this evening.

Kevin Hoyland · 2nd May 2022, 9:29 am

Hello and good morning Do you have a up date and some photos.
Thank You.
Kevin.

Cruisin Marine · 2nd May 2022, 10:14 pm

That stuff can be a nightmare to remove in nooks and crannies- might be worth using a compressor if need be, before it dry's too.

FrankB · 4th May 2022, 2:47 am

If those caps under the chassis blew up, there is a good chance any other caps by the same mfgr. are going bad also. Might as well replace them while you are in the set.
it will save heartache at a later date.

Craig Sawyers · 4th May 2022, 10:13 am

The main smoother is a dual Plessey unit. These are usually exceptionally reliable.

It depends on how much restoration has been done - if nothing, prime candidates are umpteen Hunts paper capacitors which can be anything from OK, to short or open circuit.

Or a valve has gone west. It could be the GZ34 rectifier gone pop or shorted.

Send some close up pics, and we'll have a good look.

Consider joining the Racal RA17 groups on .io

Craig

27th Apr 2022, 2:20 pm	#1
lightning Heptode Join Date: Nov 2008 Location: Stockport, Cheshire, UK. Posts: 712	RA17 gone bang l turned on my Racal RA17 last week and after a few minutes working normally there was a fairly loud bang from inside the cabinet followed by a quantity of smoke. Short of sabotage by the Russians, what should l be looking for? l took the top cover off but everything is inside metal cans, all you can see is the valves really. The radio is now dead. l assume it's blown a fuse somewhere, it's gone back into the spare room in disgrace along with the dusty "that looks a good idea" jogging machine and cheap electric bike that won't charge.

27th Apr 2022, 2:36 pm	#2
vosperd Hexode Join Date: Oct 2007 Location: Bristol, UK. Posts: 446	Re: RA17 gone bang The HT smoothing capacitor C198 and C206 is good candidate. Mounted horizontally under the chassis. If not there is a good chance there will be some other visible evidence. Don m5aky

27th Apr 2022, 2:46 pm	#3
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,965	Re: RA17 gone bang If the smoother has gone bang it will have blown the end out - it should be very obvious. There may be gunk all over the place too.

27th Apr 2022, 3:08 pm	#4
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: RA17 gone bang Mains suppression cap across the mains input ? __________________ G8JET BVWS Archivist and Member V.M.A.R.S

27th Apr 2022, 3:13 pm	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,899	Re: RA17 gone bang I wouldn't delay. The guck from exploded or leaky capacitors can be corrosive. It'll be a smaller job done sooner rather than later. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

27th Apr 2022, 3:56 pm	#6
lightning Heptode Join Date: Nov 2008 Location: Stockport, Cheshire, UK. Posts: 712	Re: RA17 gone bang Thank you for the advice. l'll get on to it this evening.

2nd May 2022, 9:29 am	#7
Kevin Hoyland Heptode Join Date: Feb 2009 Location: Rotherham, South Yorkshire, UK. Posts: 559	Re: RA17 gone bang Hello and good morning Do you have a up date and some photos. Thank You. Kevin.

2nd May 2022, 10:14 pm	#8
Cruisin Marine Octode Join Date: Jul 2018 Location: Worthing, West Sussex, UK. Posts: 1,002	Re: RA17 gone bang That stuff can be a nightmare to remove in nooks and crannies- might be worth using a compressor if need be, before it dry's too.

4th May 2022, 2:47 am	#9
FrankB Heptode Join Date: Oct 2005 Location: Olympia, Washington, USA. Posts: 664	Re: RA17 gone bang If those caps under the chassis blew up, there is a good chance any other caps by the same mfgr. are going bad also. Might as well replace them while you are in the set. it will save heartache at a later date.

4th May 2022, 10:13 am	#10
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,991	Re: RA17 gone bang The main smoother is a dual Plessey unit. These are usually exceptionally reliable. It depends on how much restoration has been done - if nothing, prime candidates are umpteen Hunts paper capacitors which can be anything from OK, to short or open circuit. Or a valve has gone west. It could be the GZ34 rectifier gone pop or shorted. Send some close up pics, and we'll have a good look. Consider joining the Racal RA17 groups on .io Craig __________________ Doomed for a certain term to walk the night