470K & 1 Meg Switched Pots no longer made. - UK Vintage Radio Repair and Restoration Discussion Forum

David G4EBT · 13th Dec 2022, 10:04 am

There was a recent thread entitled "DAC90A with broken DPDT switch help" to which I responded:

https://www.vintage-radio.net/forum/...d.php?t=195903

I'd suggested that Bowood Electronic might be worth a try as for some years they'd been the only firm that I knew of who were able to supply switched log 470K pots as replacements for the 500k Bush DAC90A volume control, and 1 Meg log pots as used by other vintage radios:

https://www.bowood-electronics.co.uk...-log-switched/

Bowood Electronics is a small family firm at Chesterfield run by Will and his wife Janet, who for many years worked for Bardwell's in Sheffield. They will be familiar to rally goers in the South Yorks area, often seen at radio rallies over the years. Their website is well worth a browse.

When I checked the stock at Bowood I noted that both 470K and 1 Meg were out of stock, and had been for a while.

At post #7 of the above thread I suggested that the only other option would be to try Blore Edwards, who will tailor-make switched and unswitched pots with any type of track, and will make a 500K log pot with double pole mains switch, though you'd need to specify all the parameters of what you need as they make them to order. That does have the advantage that you can specify a 6.34mm (1/4") spindle, which will be metal, like the original on the DAC90A, rather than a 6mm plastic shaft that most pots have these days, but I guess it would probably cost more than most DAC90A restorers would be willing to pay, (though I know at least one who has done).

I dropped an email to Will at Bowood:

Quote:

"Hi Will,

I see that for a while now you've been out of stock of 1 Mg and 470K switched log potentiometers, which are used from time to time by vintage radio restorers. Are you able to give me any indications when these might be back in stock please?"

End quote.

I've just received his response, which does at least provide a 'work-around':

Quote:

"Yes, if you can give me any indication where I can buy them. These have been discontinued with all my suppliers. With very little demand for high value switched pots it’s unlikely they will ever be produced again. All tv’s, modern radio’s etc are all digital and don’t use potentiometers. You might get lucky on the surplus market or anyone with some old stock".

Good luck with your search.

"The only thing I can offer you would be a 470K linear switched pot and an identical 470K log unswitched pot, the tracks are easily interchangeable, the only problem you will find is that when you have swapped the tracks if turn the control right back just before it clicks off there is still some resistance there, this means you won't be able to turn the volume completely off until you switch off. Kind Regards, Will".

End quote.

The DAC90A is a very commonplace radio, and hardly a day passes on the forum when '90As pop up in one thread or another, with the volume control being one of several known points of failure. That being so, maybe the BVWS could consider getting a batch made by Blore Edwards for sale as a service to to BVWS members only, as they do with the range of capacitors that they stock. I dare say that an order of perhaps 25 would bring the cost down to an acceptable price with a margin towards BVWS operating costs.

Just a thought.

vidjoman · 13th Dec 2022, 10:17 am

There are 500k and 1m LOG pots available from the US. They only have a single pole switch, are 24mm dia and have a long shaft.
Available from - https://www.tubesandmore.com/product...eters_0?page=2
No connection with them but I've had parts from them in the past. Check out the POST & PACKING etc. as it can be an additional cost to make it prohibitive. Haven't ordered anything for a couple of years. Ordered valves and they arrived well packed and promptly.

Craig Sawyers · 13th Dec 2022, 10:57 am

Blore Edwards have them https://www.blore-ed.com/product-pag...-potentiometer

Ignore the huge minimum order charge, and email them. They sell small orders if you just contact them.

Lots of options. Shaft size and length. Metal or nylon shaft, Bush size. Switch form. Linear, log, reverse log.

And 470k and 1M are standard values. And 2M and 5M too.

Craig

David G4EBT · 13th Dec 2022, 2:26 pm

Yes, I mentioned Blore Edwards at post #7 in the thread in my post above Craig, and the specification criteria, suggesting that the person who wanted the pot might wish to give Brett Cryer at Blore Edwards a call, which might save the rigmarole of going through all the ordering criteria.

I wrote:

Quote:

It looks like the only source would be Blore Edwards Ltd, who will make a 500K log pot with double pole mains switch, though you'd need to specify all the parameters of what you need as thy make them to order. That does have the advantage that you can specify a 6.34mm (1/4") spindle, which will be metal, like the original on the DAC90A, rather than a 6mm wibbly-wobbly plastic shaft that most pots have these days.

What the DAC90A requires is a 'TYPE AR-45 - Single gang with AR MAINS switch'

Specification criteria:

R = Resistance value L = Law (linear, logarithmic or reverse logarithmic)
A = Shaft length from the mounting face (FMF)
B = Bush type, 1/4"(6.35mm), 3/8"(9.5mm) or M10
C = Length of flat if requested
D = Diameter of spindle 3.18mm, 4mm, 6mm or 6.35mm (other diameters are available on request)
E = Depth of flat (5.54mm is standard)
F = Angle of flat (measured from extreme CCW position)
G = Terminal option (solder or PCB)
H = Mains variation (see Mains Switch Contact Arrangement for part numbers)

Unquote.

I rather suspect the the price for a one-off might be more than most impecunious '90A restorers will be willing to pay, but as I mentioned, I do know one forum member who did. Anyone who needs one, will need to do the 'leg-work'. (If the said forum member who bought one from B.E. is reading this, he might wish to let us know how much it cost!)

Craig Sawyers · 13th Dec 2022, 7:02 pm

I must admit I did not follow the links David

And I did not read far enough down your mail either

Oops!

Craig

Pamphonica · 13th Dec 2022, 7:28 pm

From memory, my custom pots from Blore Edwards, including a fiendish twin antilog 1Meg were all under a tenner each including postage, but this was a few years back. Try asking for Brett Cryer. He has been exceptionally helpful in the past. Worth a phone call.

David G4EBT · 13th Dec 2022, 9:10 pm

Quote:

Originally Posted by Craig Sawyers

I must admit I did not follow the links David

And I did not read far enough down your mail either

Oops!

Craig

That's to be expected Craig - I forget to add the warning: 'Reading this might induce drowsiness'!!

joebog1 · 13th Dec 2022, 10:22 pm

May I be cheeky ? Craig.

It might induce education too!!

Joe ducks

Nuvistor · 14th Dec 2022, 12:18 am

Quote:

Originally Posted by vidjoman

There are 500k and 1m LOG pots available from the US. They only have a single pole switch, are 24mm dia and have a long shaft.
Available from - https://www.tubesandmore.com/product...eters_0?page=2
No connection with them but I've had parts from them in the past. Check out the POST & PACKING etc. as it can be an additional cost to make it prohibitive. Haven't ordered anything for a couple of years. Ordered valves and they arrived well packed and promptly.

Careful with that switch, it’s rated at 125VAC.

JonSnell · 14th Dec 2022, 1:45 pm

Current production through RS
https://uk.rs-online.com/web/p/potentiometers/0387880
https://uk.rs-online.com/web/p/potentiometers/7456781
Hanging a 680k between pin 1 and pin 2 (wiper) will roughly mimmick Log.

FrankB · 21st Dec 2022, 11:42 am

You might try Mark Oppat here in the States. He has a good stash of snap together control parts and can make up pots to spec.
Contact info; moppat at comcast.net (Use correct symbol and remove spaces).
I have purchased from him over the years and is a good chap.

13th Dec 2022, 10:04 am	#1
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,763	470K & 1 Meg Switched Pots no longer made. There was a recent thread entitled "DAC90A with broken DPDT switch help" to which I responded: https://www.vintage-radio.net/forum/...d.php?t=195903 I'd suggested that Bowood Electronic might be worth a try as for some years they'd been the only firm that I knew of who were able to supply switched log 470K pots as replacements for the 500k Bush DAC90A volume control, and 1 Meg log pots as used by other vintage radios: https://www.bowood-electronics.co.uk...-log-switched/ Bowood Electronics is a small family firm at Chesterfield run by Will and his wife Janet, who for many years worked for Bardwell's in Sheffield. They will be familiar to rally goers in the South Yorks area, often seen at radio rallies over the years. Their website is well worth a browse. When I checked the stock at Bowood I noted that both 470K and 1 Meg were out of stock, and had been for a while. At post #7 of the above thread I suggested that the only other option would be to try Blore Edwards, who will tailor-make switched and unswitched pots with any type of track, and will make a 500K log pot with double pole mains switch, though you'd need to specify all the parameters of what you need as they make them to order. That does have the advantage that you can specify a 6.34mm (1/4") spindle, which will be metal, like the original on the DAC90A, rather than a 6mm plastic shaft that most pots have these days, but I guess it would probably cost more than most DAC90A restorers would be willing to pay, (though I know at least one who has done). I dropped an email to Will at Bowood: Quote: "Hi Will, I see that for a while now you've been out of stock of 1 Mg and 470K switched log potentiometers, which are used from time to time by vintage radio restorers. Are you able to give me any indications when these might be back in stock please?" End quote. I've just received his response, which does at least provide a 'work-around': Quote: "Yes, if you can give me any indication where I can buy them. These have been discontinued with all my suppliers. With very little demand for high value switched pots it’s unlikely they will ever be produced again. All tv’s, modern radio’s etc are all digital and don’t use potentiometers. You might get lucky on the surplus market or anyone with some old stock". Good luck with your search. "The only thing I can offer you would be a 470K linear switched pot and an identical 470K log unswitched pot, the tracks are easily interchangeable, the only problem you will find is that when you have swapped the tracks if turn the control right back just before it clicks off there is still some resistance there, this means you won't be able to turn the volume completely off until you switch off. Kind Regards, Will". End quote. The DAC90A is a very commonplace radio, and hardly a day passes on the forum when '90As pop up in one thread or another, with the volume control being one of several known points of failure. That being so, maybe the BVWS could consider getting a batch made by Blore Edwards for sale as a service to to BVWS members only, as they do with the range of capacitors that they stock. I dare say that an order of perhaps 25 would bring the cost down to an acceptable price with a margin towards BVWS operating costs. Just a thought. __________________ David. BVWS Member. G-QRP Club member 1339.

13th Dec 2022, 10:17 am	#2
vidjoman Dekatron Join Date: Jun 2013 Location: East Sussex, UK. Posts: 3,326	Re: 470K & 1 Meg Switched Pots no longer made. There are 500k and 1m LOG pots available from the US. They only have a single pole switch, are 24mm dia and have a long shaft. Available from - https://www.tubesandmore.com/product...eters_0?page=2 No connection with them but I've had parts from them in the past. Check out the POST & PACKING etc. as it can be an additional cost to make it prohibitive. Haven't ordered anything for a couple of years. Ordered valves and they arrived well packed and promptly.

13th Dec 2022, 10:57 am	#3
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,991	Re: 470K & 1 Meg Switched Pots no longer made. Blore Edwards have them https://www.blore-ed.com/product-pag...-potentiometer Ignore the huge minimum order charge, and email them. They sell small orders if you just contact them. Lots of options. Shaft size and length. Metal or nylon shaft, Bush size. Switch form. Linear, log, reverse log. And 470k and 1M are standard values. And 2M and 5M too. Craig __________________ Doomed for a certain term to walk the night

13th Dec 2022, 2:26 pm	#4
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,763	Re: 470K & 1 Meg Switched Pots no longer made. Yes, I mentioned Blore Edwards at post #7 in the thread in my post above Craig, and the specification criteria, suggesting that the person who wanted the pot might wish to give Brett Cryer at Blore Edwards a call, which might save the rigmarole of going through all the ordering criteria. I wrote: Quote: It looks like the only source would be Blore Edwards Ltd, who will make a 500K log pot with double pole mains switch, though you'd need to specify all the parameters of what you need as thy make them to order. That does have the advantage that you can specify a 6.34mm (1/4") spindle, which will be metal, like the original on the DAC90A, rather than a 6mm wibbly-wobbly plastic shaft that most pots have these days. What the DAC90A requires is a 'TYPE AR-45 - Single gang with AR MAINS switch' Specification criteria: R = Resistance value L = Law (linear, logarithmic or reverse logarithmic) A = Shaft length from the mounting face (FMF) B = Bush type, 1/4"(6.35mm), 3/8"(9.5mm) or M10 C = Length of flat if requested D = Diameter of spindle 3.18mm, 4mm, 6mm or 6.35mm (other diameters are available on request) E = Depth of flat (5.54mm is standard) F = Angle of flat (measured from extreme CCW position) G = Terminal option (solder or PCB) H = Mains variation (see Mains Switch Contact Arrangement for part numbers) Unquote. I rather suspect the the price for a one-off might be more than most impecunious '90A restorers will be willing to pay, but as I mentioned, I do know one forum member who did. Anyone who needs one, will need to do the 'leg-work'. (If the said forum member who bought one from B.E. is reading this, he might wish to let us know how much it cost!) __________________ David. BVWS Member. G-QRP Club member 1339.

13th Dec 2022, 7:02 pm	#5
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,991	Re: 470K & 1 Meg Switched Pots no longer made. I must admit I did not follow the links David And I did not read far enough down your mail either Oops! Craig __________________ Doomed for a certain term to walk the night

13th Dec 2022, 7:28 pm	#6
Pamphonica Nonode Join Date: Mar 2008 Location: Virginia Water, Surrey, UK. Posts: 2,877	Re: 470K & 1 Meg Switched Pots no longer made. From memory, my custom pots from Blore Edwards, including a fiendish twin antilog 1Meg were all under a tenner each including postage, but this was a few years back. Try asking for Brett Cryer. He has been exceptionally helpful in the past. Worth a phone call. __________________ Jeremy, G8MLK, BVWTVM Friend, VMARS, BVWS Secretary. www.pamphonic.co.uk www.bttt.org.uk

13th Dec 2022, 10:22 pm	#8
joebog1 Banned Join Date: Jun 2015 Location: Mareeba, North Queensland, Australia Posts: 2,704	Re: 470K & 1 Meg Switched Pots no longer made. May I be cheeky ? Craig. It might induce education too!! Joe ducks

14th Dec 2022, 1:45 pm	#10
JonSnell Hexode Join Date: Oct 2019 Location: Weymouth, Dorset, UK. Posts: 476	Re: 470K & 1 Meg Switched Pots no longer made. Current production through RS https://uk.rs-online.com/web/p/potentiometers/0387880 https://uk.rs-online.com/web/p/potentiometers/7456781 Hanging a 680k between pin 1 and pin 2 (wiper) will roughly mimmick Log. __________________ Valve equipment repairs since 1968 https://jonsnell.co.uk

21st Dec 2022, 11:42 am	#11
FrankB Heptode Join Date: Oct 2005 Location: Olympia, Washington, USA. Posts: 664	Re: 470K & 1 Meg Switched Pots no longer made. You might try Mark Oppat here in the States. He has a good stash of snap together control parts and can make up pots to spec. Contact info; moppat at comcast.net (Use correct symbol and remove spaces). I have purchased from him over the years and is a good chap.