Multiple Terminal Wafer Switch Repair - UK Vintage Radio Repair and Restoration Discussion Forum

David Dunlop · 3rd Jan 2018, 11:28 pm

Has anyone ever attempted this type of work?

I have a Main Set Receiver for a Wireless Set No. 52 Cdn, within which the Mode of Operation Switch has a broken Mid-Section Terminal Wafer. From what I have been able to determine, these types of switches were designed to be disassembled in order to replace any terminal wafer that gets damaged, rather than replacing the entire switch assembly.

Not a bad idea considering in this case I would be faced with only 6 terminals to solder/unsolder, compared to 23 to replace the entire switch.

The second challenge I see is finding the correct Mid-Section Terminal Wafer. The contact layouts vary significantly from wafer to wafer and switch to switch. I will likely have to pirate one from an otherwise perfectly good switch.

Sigh!

David

Refugee · 4th Jan 2018, 1:25 am

I rebuilt a wafer with epoxy and bits chopped from copper pipe.
The set has been working well since.

FrankB · 4th Jan 2018, 2:49 am

if the switch was made with phenolic wafers, and it was just the wafer broken, I had 100% success with repairing them with epoxy, preferably non-conductive type.
The HeathKit TT1 tube tester I got had 2 broken switches in it and the epoxy repair has only held up for 40+ years now. And that tester is my "Daily Driver".
Sure saves a lot of work.
I also have a huge box of salvaged wafers, phenolic & ceramic I keep for making my own custom switches, and for ones damaged beyond repair.
Be aware that some replacement wafers have slightly different sized spacing between the switch positions, and the screws that hold them together and the actuating shaft can be different sizes.

David Dunlop · 4th Jan 2018, 4:06 am

Thanks, Gentlemen.

I will have to take a closer look at the damage to see if any bits of the wafer are missing, or if I am lucky enough to have a clean break that can be repositioned in place. My initial look suggested the break went right up to the central shaft assembly. Two wires still connected to the free floating bit of wafer and one free wire.

David

Refugee · 4th Jan 2018, 12:05 pm

The one I did had a bit missing.
It was like dentistry but the crown was made of copper.

60 oldjohn · 4th Jan 2018, 2:08 pm

Hi David, I have these used wafers and some new ones, if you can make use of any I will send you one. size is 39mm bolt hole centres and large ones 49mm. I can take more pictures if it will help.

John.

Ed_Dinning · 4th Jan 2018, 9:05 pm

Hi David, as you can see from John's pictures there are quite a few varieties of wafer available. That said, it is still possible to re-purpose old ones and parts are always worth keeping.
If it was a Plessey switch, they used to make a switch kit, so it was possible to build your own wafers.

Ed

G6Tanuki · 4th Jan 2018, 9:20 pm

Quote:

Originally Posted by Ed_Dinning

If it was a Plessey switch, they used to make a switch kit, so it was possible to build your own wafers.

Was that the same as the RS "Maka-Switch" kit? I remember using a lot of them to make up odd switch assemblies - as well as the phenolic wafers there was a series of mains-rated on/off switches that could be fitted to the end of the spindle that also carried multiway phenolic wafers.

If ceramic wafers for your switch would be acceptable, could be worth looking here:

http://www.electro-nc.com/crl.cfm

and http://www.electro-nc.com/cat_am.shtml

"Electroswitch" took over the 'Centralab' company who were the big provider of such switches to the continental USA/Canada for decades. You may find your failed switch is a Centralab in disguise!

David Dunlop · 5th Jan 2018, 5:59 am

Thanks for the offer, John. I will take some measurements this weekend and post a photo of what this wee beastie looks like.

David

Ed_Dinning · 5th Jan 2018, 9:15 pm

Hi, no the Plessey kit had wafers, contacts, centre rings and even a jig so you could make up shorting type wafers for use in coil packs.
They do occasionally appear on ebay.

Ed

David Dunlop · 10th Jan 2018, 1:22 am

Hello John. Sorry for the delay in getting back to you. I stumbled across a complete switch assembly on the weekend and will be able to swap out the middle wafer assy in the receiver.

Thought of a full switch replacement, then I took a close look at the set and decided the wafer swap was more sensible.

Best regards,

David

3rd Jan 2018, 11:28 pm	#1
David Dunlop Pentode Join Date: Oct 2013 Location: Winnipeg, Canada Posts: 116	Multiple Terminal Wafer Switch Repair Has anyone ever attempted this type of work? I have a Main Set Receiver for a Wireless Set No. 52 Cdn, within which the Mode of Operation Switch has a broken Mid-Section Terminal Wafer. From what I have been able to determine, these types of switches were designed to be disassembled in order to replace any terminal wafer that gets damaged, rather than replacing the entire switch assembly. Not a bad idea considering in this case I would be faced with only 6 terminals to solder/unsolder, compared to 23 to replace the entire switch. The second challenge I see is finding the correct Mid-Section Terminal Wafer. The contact layouts vary significantly from wafer to wafer and switch to switch. I will likely have to pirate one from an otherwise perfectly good switch. Sigh! David

4th Jan 2018, 1:25 am	#2
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: Multiple Terminal Wafer Switch Repair I rebuilt a wafer with epoxy and bits chopped from copper pipe. The set has been working well since.

4th Jan 2018, 2:49 am	#3
FrankB Heptode Join Date: Oct 2005 Location: Olympia, Washington, USA. Posts: 664	Re: Multiple Terminal Wafer Switch Repair if the switch was made with phenolic wafers, and it was just the wafer broken, I had 100% success with repairing them with epoxy, preferably non-conductive type. The HeathKit TT1 tube tester I got had 2 broken switches in it and the epoxy repair has only held up for 40+ years now. And that tester is my "Daily Driver". Sure saves a lot of work. I also have a huge box of salvaged wafers, phenolic & ceramic I keep for making my own custom switches, and for ones damaged beyond repair. Be aware that some replacement wafers have slightly different sized spacing between the switch positions, and the screws that hold them together and the actuating shaft can be different sizes.

4th Jan 2018, 4:06 am	#4
David Dunlop Pentode Join Date: Oct 2013 Location: Winnipeg, Canada Posts: 116	Re: Multiple Terminal Wafer Switch Repair Thanks, Gentlemen. I will have to take a closer look at the damage to see if any bits of the wafer are missing, or if I am lucky enough to have a clean break that can be repositioned in place. My initial look suggested the break went right up to the central shaft assembly. Two wires still connected to the free floating bit of wafer and one free wire. David

4th Jan 2018, 12:05 pm	#5
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: Multiple Terminal Wafer Switch Repair The one I did had a bit missing. It was like dentistry but the crown was made of copper. Attached Thumbnails

4th Jan 2018, 2:08 pm	#6
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,990	Re: Multiple Terminal Wafer Switch Repair Hi David, I have these used wafers and some new ones, if you can make use of any I will send you one. size is 39mm bolt hole centres and large ones 49mm. I can take more pictures if it will help. John. Attached Thumbnails

4th Jan 2018, 9:05 pm	#7
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Multiple Terminal Wafer Switch Repair Hi David, as you can see from John's pictures there are quite a few varieties of wafer available. That said, it is still possible to re-purpose old ones and parts are always worth keeping. If it was a Plessey switch, they used to make a switch kit, so it was possible to build your own wafers. Ed

5th Jan 2018, 5:59 am	#9
David Dunlop Pentode Join Date: Oct 2013 Location: Winnipeg, Canada Posts: 116	Re: Multiple Terminal Wafer Switch Repair Thanks for the offer, John. I will take some measurements this weekend and post a photo of what this wee beastie looks like. David

5th Jan 2018, 9:15 pm	#10
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Multiple Terminal Wafer Switch Repair Hi, no the Plessey kit had wafers, contacts, centre rings and even a jig so you could make up shorting type wafers for use in coil packs. They do occasionally appear on ebay. Ed

10th Jan 2018, 1:22 am	#11
David Dunlop Pentode Join Date: Oct 2013 Location: Winnipeg, Canada Posts: 116	Re: Multiple Terminal Wafer Switch Repair Hello John. Sorry for the delay in getting back to you. I stumbled across a complete switch assembly on the weekend and will be able to swap out the middle wafer assy in the receiver. Thought of a full switch replacement, then I took a close look at the set and decided the wafer swap was more sensible. Best regards, David