Type of Switch? - UK Vintage Radio Repair and Restoration Discussion Forum

Andrew B · 24th Oct 2016, 10:57 pm

Hi All.

I have spent quite a time looking through "auction sites" looking for this type of rotary switch. Is there a special name for them or are they just very uncommon?
https://www.vintage-radio.net/forum/...pictureid=3559

Thanks
Andrew

Station X · 24th Oct 2016, 11:07 pm

Bridging Rotary Switch.

M0FYA Andy · 25th Oct 2016, 9:27 am

Was this type of switch ever available as a stock item, or were they only a bespoke item for a production run? So a problem to replace or to find for a one-off 'home-brew' design.
Andy

Andrew B · 25th Oct 2016, 10:59 am

I have hunted high and low for them, I want to make an ATU that progressively shorts the unused turns to ground. I have looked at the possibility of >hacking< some switches around. Someone out there must make them !!

ms660 · 25th Oct 2016, 11:22 am

Can't see any picture when I click on that the link, just a dark blank screen....

EDIT: Ignore above, can see it now.

Lawrence.

Station X · 25th Oct 2016, 11:28 am

I've had a quick look at some homebrew ATU designs in old RSGB and ARRL books, but none of them use this type of switch. Ordinary switches, croc clips on the coils and Roller Coasters appear to have been the norm. This makes me think this type of switch may not have been on general sale.

Skywave · 25th Oct 2016, 11:52 am

I'm a little bit confused by the drawing of that switch. I can see and understand that the contact drawn as the horizontal arrow on the right always makes contact with the central-sectored rotor. What I don't understand is the contact that is shown as connected to what appears to be the spindle of the switch. Is that meant to signify that that spindle should be earthed?

Anyway, having said all that, I reckon that that switch is a 'one-off special'. But you might be able to meet your need by modifying the type of rotary switch that is used to select one coil from a range of other coils: commonly used as a 'band select' switch. That type of switch selects one coil and short-circuits all the others to avoid unwanted resonances. Alternatively, it might be possible to achieve the required result with a multi-wafer rotary switch that has various and different selection arrangements per wafer.

Going off on a tangent and depending on the required switch's application, perhaps an arrangement of electronic switches may be configurable and suitable.

Al.

M0FYA Andy · 25th Oct 2016, 11:52 am

I can't see why you need this type of switch, surely as you tap up the coil all the turns below the tap are shorted to ground anyway?
Having said that, how many positions would you require? I have recently dismantled one of the Tuning Units for the BC-375 transmitter. (Don't worry, it was already partly robbed when I got it, I wouldn't dismantle a good one). One of the switches removed is of this configuration, four positions with no connection and then three with connections, so 'three taps worth'.
Also a nice switch with six contacts, but simply switching around them.
Both are high-quality well-spaced ceramic transmitting types.
If either are of any use for your project let me know.

Andy

ms660 · 25th Oct 2016, 12:20 pm

Not sure how many contacts you need but an old "Fireball" tv tuner normally has 8 fitted and has 13 rotary positions, the biscuit contacts can be shorted out to suit, ok for low power and if you have the room....Just a thought:

https://www.vintage-radio.net/forum/...ead.php?t=6316

Lawrence.

Top Cap · 25th Oct 2016, 1:16 pm

As mentioned by Skywave, the only off-the-shelf shorting switch I know of is Farnell 146041 but only allows one un-shorted position at a time. You would need the mechanism 146033. I used these for a test box making sensitive measurements on fuzes to safeguard against unwanted explosions

Still in use today as a safe continuity tester, a commercial equivalent was many hundreds of pounds to buy.

Andrew B · 25th Oct 2016, 1:40 pm

As luck would have it, I have found a switch manufacturer less than 5 miles from me www.nsfcontrols.co.uk who advertise all sorts of switches of the rotary variety.

I sent the technical department an email, a description and the circuit diagram of a Yaesu FC-500 ATU. It seems that many commercial ATU'a "ground out" or "add" parts of the tuning coil together in order to achieve the range of inductance.

https://www.vintage-radio.net/forum/...pictureid=3560

It should be possible to switch the coil with just 1 wafer "making" (adding) additional turns. I can't believe that only a tiny percentage of rotary switches are "bridging"

Andrew B · 25th Oct 2016, 4:42 pm

Hmm, they weren't much help AT ALL, however, digging in my junk box I found a switch that with help from my dremel, will probably do the job............ now all I need is a trip to the model shop to buy some 3/32" brass pipe to make the rivets

Ed_Dinning · 25th Oct 2016, 7:55 pm

Hi Andrew, these type of switches were often made up for experimental purposes using a Plessey switch kit, once commonly found in most dev labs and very useful for this type of job, It contains all the wafers, contacts and rings needed for a wide variety of configurations. The best bit are the small eyelet pliers used to close the eyelets on the contacts.
They occasionally appear on e-bay, I managed to get one a few years ago

Ed

Andrew B · 25th Oct 2016, 11:07 pm

Yes, Thanks ED, strangely enough, this switch I have was made by NSF (who just replied to my email with lots of drivel

Quote:

Hi Andrew,
Unfortunately I don't think that it will be that simple.
As a manufacturer all our products are subject to Minimum order quantities and we have a £100 minimum order amount.
I suspect that is more than you are expecting to pay for your bits and pieces.
The ceramic wafers themselves are expensive items to make and we do not carry stock.

I think that you said that you have tried the distributors, but I think that might still be your most viable option.
Regards,
Karen

Karen Carpenter
COMMERCIAL ADMINISTRATOR
NSF Controls Ltd, Ingrow Bridge Works, Keighley, West Yorkshire, BD21 5EF, UK
Registered in England No. 3378269

Says it all really, they probably buy the switches ready-made from China, put a company logo on them and mark up the price as well!!

I should be able to make the rivets/eyelet things out of some annealed copper tube from the local model shop (3/32" OD) or 2.32mm, I can spin up a little mandrel from piano wire/HSS stock that should make a neat job of buttoning up the eyelets that secure the contacts to the wafer. I have plenty of the periphery contacts and the rotary "contactor bit" in the middle looks set to meet my dremel.

I am going to more or less copy the Yaesu design above as I have enough wafers and quite a few push on/push off switches laid about, including an old SWR meter that will follow the same fate.

Thanks for everyones feedback so far.

Andrew

ChristianFletcher · 26th Oct 2016, 11:00 am

Not the same thing, but I once constructed something similar using a normal rotary switch and a bank of relays to do the switching. I used diode logic to program the switch control sequences.

I also once built a high powered decade resistance box, but used one multi turn encoder and a microcontroller to pull in various resistor values. I remember at the time it was much cheaper given the cost of the switches.

ms660 · 26th Oct 2016, 11:36 am

An old type barrel switch is within the realms of DIY:

http://www.americanradiohistory.com/...ical%20hole%22

Brass grub screws could be used for the turret contacts, they can be linked to give progressive shorting of the ATU coil.

Lawrence.

Skywave · 26th Oct 2016, 12:50 pm

Andrew: re the drawing in your post #1. That drawing looks incorrect to me. I say that because as it is drawn, there a three contacts on the left of the switch and one on the right that will always make contact with the central rotor selector, irrespective of the position of that rotor. However, if those contacts were drawn so that they were not in contact with that central rotor, but only made contact with the extended segment that is shown in the lower part of the drawing, to me, that would make a lot more sense. And I still don't understand why there is a contact shown to (presumably) the central spindle of the switch.

Can you enlighten me on these points, please?

Al.

Station X · 26th Oct 2016, 1:03 pm

It makes a bit more sense if you look at the complete picture.

https://www.vintage-radio.net/forum/...pictureid=3560

Skywave · 26th Oct 2016, 2:03 pm

Ah! The complete picture reveals what I suspected: the switches are drawn in a misleading fashion - well, misleading to me! Thank you, Graham.

So it seems that the 'pointed contacts' that are shown making a point contact with the shaped rotor do not make a permanent contact at all with that rotor and that it is only the extended section of the rotor that makes such contacts, depending on the position of the switch.
It is also apparent (now) that the contact that is shown pointing to the centre of the rotor is the 'draughtman's' attempt to indicate that that connection is always joined to the rotor, irrespective of the rotor's position.

Now not only does all of that now makes sense

, but it has also given me food for thought . . .

Al.

Station X · 26th Oct 2016, 2:07 pm

It looks to me as if some of the switch wafers in that circuit do not need to be of the bridging type at all.

24th Oct 2016, 11:07 pm	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Type of Switch? Bridging Rotary Switch. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

25th Oct 2016, 9:27 am	#3
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: Type of Switch? Was this type of switch ever available as a stock item, or were they only a bespoke item for a production run? So a problem to replace or to find for a one-off 'home-brew' design. Andy

25th Oct 2016, 10:59 am	#4
Andrew B Heptode Join Date: May 2015 Location: Bradford, West Yorkshire, UK. Posts: 512	Re: Type of Switch? I have hunted high and low for them, I want to make an ATU that progressively shorts the unused turns to ground. I have looked at the possibility of >hacking< some switches around. Someone out there must make them !! __________________ worried about the electrons entering the circuit and the smoke leaving Andrew

25th Oct 2016, 11:22 am	#5
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Type of Switch? Can't see any picture when I click on that the link, just a dark blank screen.... EDIT: Ignore above, can see it now. Lawrence.

25th Oct 2016, 11:28 am	#6
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Type of Switch? I've had a quick look at some homebrew ATU designs in old RSGB and ARRL books, but none of them use this type of switch. Ordinary switches, croc clips on the coils and Roller Coasters appear to have been the norm. This makes me think this type of switch may not have been on general sale. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

24th Oct 2016, 10:57 pm	#1
Andrew B Heptode Join Date: May 2015 Location: Bradford, West Yorkshire, UK. Posts: 512	Type of Switch? Hi All. I have spent quite a time looking through "auction sites" looking for this type of rotary switch. Is there a special name for them or are they just very uncommon? https://www.vintage-radio.net/forum/...pictureid=3559 Thanks Andrew __________________ worried about the electrons entering the circuit and the smoke leaving Andrew Last edited by Andrew B; 24th Oct 2016 at 11:06 pm.

25th Oct 2016, 11:52 am	#7
Skywave Rest in Peace Join Date: Jun 2006 Location: Chard, South Somerset, UK. Posts: 7,457	Re: Type of Switch? I'm a little bit confused by the drawing of that switch. I can see and understand that the contact drawn as the horizontal arrow on the right always makes contact with the central-sectored rotor. What I don't understand is the contact that is shown as connected to what appears to be the spindle of the switch. Is that meant to signify that that spindle should be earthed? Anyway, having said all that, I reckon that that switch is a 'one-off special'. But you might be able to meet your need by modifying the type of rotary switch that is used to select one coil from a range of other coils: commonly used as a 'band select' switch. That type of switch selects one coil and short-circuits all the others to avoid unwanted resonances. Alternatively, it might be possible to achieve the required result with a multi-wafer rotary switch that has various and different selection arrangements per wafer. Going off on a tangent and depending on the required switch's application, perhaps an arrangement of electronic switches may be configurable and suitable. Al.

25th Oct 2016, 11:52 am	#8
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: Type of Switch? I can't see why you need this type of switch, surely as you tap up the coil all the turns below the tap are shorted to ground anyway? Having said that, how many positions would you require? I have recently dismantled one of the Tuning Units for the BC-375 transmitter. (Don't worry, it was already partly robbed when I got it, I wouldn't dismantle a good one). One of the switches removed is of this configuration, four positions with no connection and then three with connections, so 'three taps worth'. Also a nice switch with six contacts, but simply switching around them. Both are high-quality well-spaced ceramic transmitting types. If either are of any use for your project let me know. Andy

25th Oct 2016, 12:20 pm	#9
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Type of Switch? Not sure how many contacts you need but an old "Fireball" tv tuner normally has 8 fitted and has 13 rotary positions, the biscuit contacts can be shorted out to suit, ok for low power and if you have the room....Just a thought: https://www.vintage-radio.net/forum/...ead.php?t=6316 Lawrence.

25th Oct 2016, 1:16 pm	#10
Top Cap Octode Join Date: Mar 2006 Location: Watford, Hertfordshire, UK. Posts: 1,270	Re: Type of Switch? As mentioned by Skywave, the only off-the-shelf shorting switch I know of is Farnell 146041 but only allows one un-shorted position at a time. You would need the mechanism 146033. I used these for a test box making sensitive measurements on fuzes to safeguard against unwanted explosions Still in use today as a safe continuity tester, a commercial equivalent was many hundreds of pounds to buy. __________________ Whether the Top Cap is Grid or Anode - touching it will give you a buzz either way!

25th Oct 2016, 1:40 pm	#11
Andrew B Heptode Join Date: May 2015 Location: Bradford, West Yorkshire, UK. Posts: 512	Re: Type of Switch? As luck would have it, I have found a switch manufacturer less than 5 miles from me www.nsfcontrols.co.uk who advertise all sorts of switches of the rotary variety. I sent the technical department an email, a description and the circuit diagram of a Yaesu FC-500 ATU. It seems that many commercial ATU'a "ground out" or "add" parts of the tuning coil together in order to achieve the range of inductance. https://www.vintage-radio.net/forum/...pictureid=3560 It should be possible to switch the coil with just 1 wafer "making" (adding) additional turns. I can't believe that only a tiny percentage of rotary switches are "bridging" __________________ worried about the electrons entering the circuit and the smoke leaving Andrew

25th Oct 2016, 4:42 pm	#12
Andrew B Heptode Join Date: May 2015 Location: Bradford, West Yorkshire, UK. Posts: 512	Re: Type of Switch? Hmm, they weren't much help AT ALL, however, digging in my junk box I found a switch that with help from my dremel, will probably do the job............ now all I need is a trip to the model shop to buy some 3/32" brass pipe to make the rivets __________________ worried about the electrons entering the circuit and the smoke leaving Andrew

25th Oct 2016, 7:55 pm	#13
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Type of Switch? Hi Andrew, these type of switches were often made up for experimental purposes using a Plessey switch kit, once commonly found in most dev labs and very useful for this type of job, It contains all the wafers, contacts and rings needed for a wide variety of configurations. The best bit are the small eyelet pliers used to close the eyelets on the contacts. They occasionally appear on e-bay, I managed to get one a few years ago Ed

26th Oct 2016, 11:00 am	#15
ChristianFletcher Heptode Join Date: Dec 2003 Location: South Yorkshire, UK. Posts: 900	Re: Type of Switch? Not the same thing, but I once constructed something similar using a normal rotary switch and a bank of relays to do the switching. I used diode logic to program the switch control sequences. I also once built a high powered decade resistance box, but used one multi turn encoder and a microcontroller to pull in various resistor values. I remember at the time it was much cheaper given the cost of the switches. __________________ Every Silver Lining Has Its Cloud https://youtube.com/channel/UCvBpiuUUnErJlNBm6DWb3Ww

26th Oct 2016, 11:36 am	#16
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Type of Switch? An old type barrel switch is within the realms of DIY: http://www.americanradiohistory.com/...ical%20hole%22 Brass grub screws could be used for the turret contacts, they can be linked to give progressive shorting of the ATU coil. Lawrence.

26th Oct 2016, 12:50 pm	#17
Skywave Rest in Peace Join Date: Jun 2006 Location: Chard, South Somerset, UK. Posts: 7,457	Re: Type of Switch? Andrew: re the drawing in your post #1. That drawing looks incorrect to me. I say that because as it is drawn, there a three contacts on the left of the switch and one on the right that will always make contact with the central rotor selector, irrespective of the position of that rotor. However, if those contacts were drawn so that they were not in contact with that central rotor, but only made contact with the extended segment that is shown in the lower part of the drawing, to me, that would make a lot more sense. And I still don't understand why there is a contact shown to (presumably) the central spindle of the switch. Can you enlighten me on these points, please? Al.

26th Oct 2016, 1:03 pm	#18
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Type of Switch? It makes a bit more sense if you look at the complete picture. https://www.vintage-radio.net/forum/...pictureid=3560 __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

26th Oct 2016, 2:03 pm	#19
Skywave Rest in Peace Join Date: Jun 2006 Location: Chard, South Somerset, UK. Posts: 7,457	Re: Type of Switch? Ah! The complete picture reveals what I suspected: the switches are drawn in a misleading fashion - well, misleading to me! Thank you, Graham. So it seems that the 'pointed contacts' that are shown making a point contact with the shaped rotor do not make a permanent contact at all with that rotor and that it is only the extended section of the rotor that makes such contacts, depending on the position of the switch. It is also apparent (now) that the contact that is shown pointing to the centre of the rotor is the 'draughtman's' attempt to indicate that that connection is always joined to the rotor, irrespective of the rotor's position. Now not only does all of that now makes sense , but it has also given me food for thought . . . Al. Last edited by Skywave; 26th Oct 2016 at 2:12 pm.

26th Oct 2016, 2:07 pm	#20
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Type of Switch? It looks to me as if some of the switch wafers in that circuit do not need to be of the bridging type at all. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.