Switch conundrum - UK Vintage Radio Repair and Restoration Discussion Forum

Valvepower · 16th Sep 2013, 8:29 pm

Hi There,

Don’t know if anyone can help? But I need to reassemble the switch mechanism of the pot in the attached picture.

I’ve included a picture of the switch parts etc., Which I feel are all there and accounted for.

It seems fairly straight forward, but I’m foxed by the position of the spring and any advice would be appreciated, so I’m after any instructions or a guide to reassemble the switch mechanism or a faulty pot or switch mechanism I can carefully dissemble, noting the way it was assembled

The previous owner decided to deassemble the switch to clean the contacts, as they felt there were arcing, but was unable to reassemble it, so it got put away until I got my hands on it - all be it in pieces.

I’m not sure of the manufacturer of the pot, but I feel it may be manufactured by Dubilier in the 70's. The pot is a replacement pot fitted to a Quad 22 preamplifier and therefore the pot needs to be fixed as Quad sadly no longer supplies this pot.

P.s I feel the original fault was a faulty ‘Rifa’ capacitor as I can see some ‘blackening’ of the innards of the capacitor, plus it smells ‘burnt’

Thanks in advance
Terry.

Lucien Nunes · 16th Sep 2013, 11:53 pm

I'm fairly sure I have opened one of those in the distant past, and my suggestion is that the two switch blades pivot on the two closest pins in their end holes. The two pegs on the white plastic link project through the middle holes of the blades and the short slots in the paxolin, while the spring spans between the hole in the white operating lever and that in the plastic link. As the lever moves past midway the spring snaps the link across. The projection of the main black housing that passes through the long slot in the paxolin prevents one switch blade contacting the other fixed pin when off. Whether there is a preferred direction for the coil of the spring to face I am not sure, although the shape of the interior of the housing might decide this for you.

vidjoman · 17th Sep 2013, 11:19 am

The Rifa cap is actually (or should be) a resistor + capacitor and is a suppressor. I would have thought it has been changed (probably if the pot was changed) as I recall the 22 had the small box suppressor with flying leads wired across the switch.

vinrads · 17th Sep 2013, 5:29 pm

Don't know about the switch, but I must complement you on the excellent pictures, Mick.

Philips210 · 17th Sep 2013, 8:30 pm

Hi Terry I have found a single gang pot with a similar double pole switch.

In the past, I have stripped and repaired many pots but this type looks more of a challenge to open without damaging it. The black plastic housing appears to be heat flanged around the paxolin contact panel. I would think the paxolin panel could be prised out of the housing but getting it reassembled could be a problem.
I have this spare switch in the attached pics if it is any use.

Regards
Symon.

Leon Crampin · 17th Sep 2013, 11:50 pm

The switch and pot are made by Plessey.

Leon.

Philips210 · 18th Sep 2013, 8:56 am

Hi

I have found on several occasions this type of switch suffers an odd delay in it's operation. When rotating the pot fully anti-clockwise to the off position, the switch doesn't open straight away. I have found the delay, in some cases, can be as much as seconds for the switch to click open.

Regards
Symon.

vidjoman · 18th Sep 2013, 9:53 am

I have had these switches apart, but some time ago now.
From what I remember - the last part to fit is the pot metal cover. I think the original owner took it apart 'the wrong way round'. The paxolin panel has to be fixed to the black plastic - put it down on the bench on it's solder contacts (use blu-tack or some way to stop it moving), fit the contact bars, then the small rectangular plastic actuator, then the spring and the upper plastic part. Finally fit the metal cover.
As you can see from Symon's picture in post 5 - they were originally riveted. And as he mentions they are often sluggish in operation, which I put down to grease holding it back. I don't think I would grease it as slow operation could lead to arcing of the contacts.
Think I've remembered it correctly - it's been a few years since I did one of those. Replaced a lot with the Japanese pot/switch that Quad used to send as replacements.

Valvepower · 18th Sep 2013, 2:22 pm

Hi All,

Firstly many thanks for all the replies to this thread and the reassembly descriptions.

I’ll have a go at reassembling the one I have here but Symon, I may well take you up on your offer of a replacement switch as this may be a better long term bet. I’ll contact Symon via a PM later today.

Thanks Mick, for the kind comments regarding the photo. I’ll contact you via a PM later today to let you know the model and make of camera.

Regards the Rifa capacitors and yes, they were replacement parts, presumably fitted by Quad when the pot was replaced. Yes, the 22 had the small box suppressor with flying leads, as I have a faulty one on the odds ends box. I know there is a thread on the forum concerning the premature failure of the Rifa parts; you can add this one to the list!

Ah, it’s a Plessey pot. I vaguely remember RS supplied Plessey pots (in nice cardboard boxes) at one time, this was before they used AB in bags … I may be wrong but it was a long time ago!

Regards
Terry.

Valvepower · 24th Sep 2013, 8:31 pm

Hi,

Thanks to Symon I’ve received the switch – thanks.

Regarding the switch I recon I have three options:

1/ Strip down the pot and switch in the Quad and fit the switch

2/ Dissemble the switch to see how it was assembled

3/ Inspect – as best I can – the way the switch is assembled (without disassembling it!) and work out a way of reassembling the switch in the Quad using your (assembled) switch as guide as to placing the switch components back in the correct way using the correct method.

I’ll let you know how I get on.

Regards
Terry.

16th Sep 2013, 8:29 pm	#1
Valvepower Octode Join Date: Aug 2008 Location: Rayleigh near Southend-On-Sea, Essex, UK. Posts: 1,879	Switch conundrum Hi There, Don’t know if anyone can help? But I need to reassemble the switch mechanism of the pot in the attached picture. I’ve included a picture of the switch parts etc., Which I feel are all there and accounted for. It seems fairly straight forward, but I’m foxed by the position of the spring and any advice would be appreciated, so I’m after any instructions or a guide to reassemble the switch mechanism or a faulty pot or switch mechanism I can carefully dissemble, noting the way it was assembled The previous owner decided to deassemble the switch to clean the contacts, as they felt there were arcing, but was unable to reassemble it, so it got put away until I got my hands on it - all be it in pieces. I’m not sure of the manufacturer of the pot, but I feel it may be manufactured by Dubilier in the 70's. The pot is a replacement pot fitted to a Quad 22 preamplifier and therefore the pot needs to be fixed as Quad sadly no longer supplies this pot. P.s I feel the original fault was a faulty ‘Rifa’ capacitor as I can see some ‘blackening’ of the innards of the capacitor, plus it smells ‘burnt’ Thanks in advance Terry. Attached Thumbnails

16th Sep 2013, 11:53 pm	#2
Lucien Nunes Rest in Peace Join Date: Apr 2008 Location: London, UK. Posts: 2,508	Re: Switch conundrum I'm fairly sure I have opened one of those in the distant past, and my suggestion is that the two switch blades pivot on the two closest pins in their end holes. The two pegs on the white plastic link project through the middle holes of the blades and the short slots in the paxolin, while the spring spans between the hole in the white operating lever and that in the plastic link. As the lever moves past midway the spring snaps the link across. The projection of the main black housing that passes through the long slot in the paxolin prevents one switch blade contacting the other fixed pin when off. Whether there is a preferred direction for the coil of the spring to face I am not sure, although the shape of the interior of the housing might decide this for you. Last edited by Lucien Nunes; 17th Sep 2013 at 12:01 am.

17th Sep 2013, 11:19 am	#3
vidjoman Dekatron Join Date: Jun 2013 Location: East Sussex, UK. Posts: 3,326	Re: Switch conundrum The Rifa cap is actually (or should be) a resistor + capacitor and is a suppressor. I would have thought it has been changed (probably if the pot was changed) as I recall the 22 had the small box suppressor with flying leads wired across the switch.

17th Sep 2013, 5:29 pm	#4
vinrads Dekatron Join Date: Feb 2009 Location: Chesterfield, Derbyshire, UK. Posts: 3,760	Re: Switch conundrum Don't know about the switch, but I must complement you on the excellent pictures, Mick. Last edited by AC/HL; 17th Sep 2013 at 7:54 pm. Reason: Cameras discussions are off-topic for this Forum

17th Sep 2013, 8:30 pm	#5
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,573	Re: Switch conundrum Hi Terry I have found a single gang pot with a similar double pole switch. In the past, I have stripped and repaired many pots but this type looks more of a challenge to open without damaging it. The black plastic housing appears to be heat flanged around the paxolin contact panel. I would think the paxolin panel could be prised out of the housing but getting it reassembled could be a problem. I have this spare switch in the attached pics if it is any use. Regards Symon. Attached Thumbnails

17th Sep 2013, 11:50 pm	#6
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,870	Re: Switch conundrum The switch and pot are made by Plessey. Leon.

18th Sep 2013, 8:56 am	#7
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,573	Re: Switch conundrum Hi I have found on several occasions this type of switch suffers an odd delay in it's operation. When rotating the pot fully anti-clockwise to the off position, the switch doesn't open straight away. I have found the delay, in some cases, can be as much as seconds for the switch to click open. Regards Symon.

18th Sep 2013, 9:53 am	#8
vidjoman Dekatron Join Date: Jun 2013 Location: East Sussex, UK. Posts: 3,326	Re: Switch conundrum I have had these switches apart, but some time ago now. From what I remember - the last part to fit is the pot metal cover. I think the original owner took it apart 'the wrong way round'. The paxolin panel has to be fixed to the black plastic - put it down on the bench on it's solder contacts (use blu-tack or some way to stop it moving), fit the contact bars, then the small rectangular plastic actuator, then the spring and the upper plastic part. Finally fit the metal cover. As you can see from Symon's picture in post 5 - they were originally riveted. And as he mentions they are often sluggish in operation, which I put down to grease holding it back. I don't think I would grease it as slow operation could lead to arcing of the contacts. Think I've remembered it correctly - it's been a few years since I did one of those. Replaced a lot with the Japanese pot/switch that Quad used to send as replacements.

18th Sep 2013, 2:22 pm	#9
Valvepower Octode Join Date: Aug 2008 Location: Rayleigh near Southend-On-Sea, Essex, UK. Posts: 1,879	Re: Switch conundrum Hi All, Firstly many thanks for all the replies to this thread and the reassembly descriptions. I’ll have a go at reassembling the one I have here but Symon, I may well take you up on your offer of a replacement switch as this may be a better long term bet. I’ll contact Symon via a PM later today. Thanks Mick, for the kind comments regarding the photo. I’ll contact you via a PM later today to let you know the model and make of camera. Regards the Rifa capacitors and yes, they were replacement parts, presumably fitted by Quad when the pot was replaced. Yes, the 22 had the small box suppressor with flying leads, as I have a faulty one on the odds ends box. I know there is a thread on the forum concerning the premature failure of the Rifa parts; you can add this one to the list! Ah, it’s a Plessey pot. I vaguely remember RS supplied Plessey pots (in nice cardboard boxes) at one time, this was before they used AB in bags … I may be wrong but it was a long time ago! Regards Terry.

24th Sep 2013, 8:31 pm	#10
Valvepower Octode Join Date: Aug 2008 Location: Rayleigh near Southend-On-Sea, Essex, UK. Posts: 1,879	Re: Switch conundrum Hi, Thanks to Symon I’ve received the switch – thanks. Regarding the switch I recon I have three options: 1/ Strip down the pot and switch in the Quad and fit the switch 2/ Dissemble the switch to see how it was assembled 3/ Inspect – as best I can – the way the switch is assembled (without disassembling it!) and work out a way of reassembling the switch in the Quad using your (assembled) switch as guide as to placing the switch components back in the correct way using the correct method. I’ll let you know how I get on. Regards Terry.