Volume control - UK Vintage Radio Repair and Restoration Discussion Forum

hillmanie · 27th Sep 2019, 10:07 pm

Hi folks
One of my fixer uppers came DOA as listed. On the face of it this might seem an easier fix, needing only to check the continuity, plug - cable - mains switch - transformer primary. Found first beak in the combined switch/volume control, double pole, the Live terminal. Looks the same as the ubiquitous ones of yesteryear. I seem to remember this as a common fault as I think the internal switch contacts were skinny and arced at ON and OFF. In those days being even more penny pinching than now I used to unclip the switch section and brighten the contacts. I may well do so again if they're not burned out as new same type replacements are seemingly unbtainable and an s/h eBay one is dear enough not to risk something could fail soon after. To continue the testing I thought of shorting out the offending pair with the precaution of swapping the live and neutral wires first so the Live remains switched.
Does the forum think that this is too great a departure from safe practice even in the short term?
I'm looking at another option to replace the two pots with smaller modern knurled types I see a-plenty, but thinks maybe they're battery only and won't take the 250v. Contacted an Eastern gentleman purveyor as to the specs on these but without result
Any advice much thanked
TT

ColinTheAmpMan1 · 28th Sep 2019, 6:22 pm

If you let us all know what the item is (make, type) and what the specification of the switched pot is (apart from the 250VAC requirement. Resistance, log/lin) we might have a chance to rummage through our junk-boxes). A photo of the pot with some indication of physical dimensions would also be useful if you're wanting originality.
You might be pleasantly surprised at what we might come up with, but we are just treading water so far.
Colin.

John10b · 28th Sep 2019, 6:41 pm

As Colin said you may be pleasantly surprised at what is available, take a look at Blore-ed.com, they may have just what you want.
Cheers
John

hillmanie · 28th Sep 2019, 6:42 pm

Quote:

Originally Posted by ColinTheAmpMan1

If you let us all know what the item is (make, type) and what the specification of the switched pot is (

Colin.

.................................................. ......................................
Great offer Colin, thanks. I'll get the model no, of the tape recorder easily but won't be able I fear to learn any spec info by reference to the pot itself. Will certainly take a pic which will be in my Album as I haven't yet learned how to get it from there to a posting
Rgds
TT

hillmanie · 3rd Oct 2019, 10:11 pm

Quote:

Originally Posted by John10b

As Colin said you may be pleasantly surprised at what is available, take a look at Blore-ed.com,.
Cheers
John

----------------------------------------------------------------------------
Hi
Re open circuit in Live contacts of volume control, thanks for the inputs folks. I have uploaded two pics 027 and 028 to my album. Some explaining seems to be in order here. My first posting wasn't intended as a request for a replacement for the V. control but to seek reassurance on shorting out the o/c contacts. That this resulted in offers of such replacement is a measure of the generosity of members. I can't see that the pics are much help and I'll look harder to find meaningful marks. The shaft is approx 5 cm long. Meanwhile I'll get on with (awaits) swapping the wires so that the Live is switched. Am considering drilling a small hole and injecting contact cleaner whilst flicking it. Will let it dry out fully after of course
I did check out the Brod lead John as suggested. An impressing stock but nothing like my pot I fear, all rather modern looking. I noticed too the item prices reflect the quality, since I've bought on average three old r/corders for the price of one of his items.
Rgds
TT

hillmanie · 3rd Oct 2019, 10:32 pm

PS
The recorder is a Ferguson 3218
Rgds
TT

ColinTheAmpMan1 · 4th Oct 2019, 2:56 pm

Could you provide a link to your photos in your album, please? I have no knowledge of the recorder that you mention, so I don't know what the value of the pot is supposed to be, either. The value will be stamped on the metal body of the pot somewhere, together with an "A" or "B" indication of the law. I have a switched 1M log pot which might be correct, as volume pots usually have a log law, but it only has a short (1cm) shaft with a "D" cross-section.

It should be perfectly OK to short out the failed switch on the pot, so long as the LINE remains switched. It isn't ideal, of course, but it will function, even if electrical safety is marginally compromised.

It is quite simple to append pictures to posts; check out the FAQ page for how to do it. Select "Reading and Posting Messages", followed by "Attachments and Images". Good Luck.

Colin.

'LIVEWIRE?' · 4th Oct 2019, 3:30 pm

The easiest way to add attachments (Pictures) to a post is to click the 'Go Advanced' box under the 'Quick Reply' box, then follow the instructions given therein.

AC/HL · 4th Oct 2019, 3:37 pm

Or use the post reply button an the left which combines the two. Broad as long.

hillmanie · 4th Oct 2019, 8:43 pm

Thank you Colin et al. Have confirmed the ID details (label is a bit unclear). On closer scrutiny It seems to read Ferguson 3218. Also re attachments I must be losing it as it's not rocket science. Heretofore I only read the Album instructions and on making access public.
You're correct about the markings as when I loosed it I found on the back 8-4 1 megohm (the symbol) LIN (ear?) Looks like I've uploaded the two pics but they're not opening ?
For the least disturbance I'll short the contact and switch the Live and get on with a few unfinished tasks not least of which is replacing the Philips liquified belt
Rgds
TT

hillmanie · 4th Oct 2019, 8:45 pm

Correction - thought the pics didn't render but I was wrong
TT

Sideband · 5th Oct 2019, 7:39 am

Looks to be a perfectly normal 1 meg pot with switch. You can dismantle those quite easily. Take the control out completely (making a note of where everything goes) and you should find the switch will come off after straightening out the fixing tabs. A squirt of Servisol may well free up the contacts. Most times I've been able to sort these out with little effort. There isn't much current involved even taking the switch-on surge into account so unless something shorted (if there is a capacitor across the mains) then the switches don't really have a hard life.

You may not even need to remove the pot. If there is a gap between the three pot connections and the metal case, just squirt some Servisol in there and work the switch a few times and that should free up the sticky switch (if that is what the trouble is). You don't need to let it dry out (in fact Servisol shouldn't dry out completely as it leaves a lubricating film behind.

hillmanie · 5th Oct 2019, 1:52 pm

Thanks again. Not really a gap, which is why I previously mentioned I'd drill a small squirt hole. Re arcing, there's isn't a cap. across the contacts in this case
TT

Station X · 5th Oct 2019, 2:07 pm

I describe how I fixed the switch associated with a similar pot in this post:-

https://www.vintage-radio.net/forum/...0&postcount=36

ColinTheAmpMan1 · 5th Oct 2019, 2:07 pm

Quote:

Originally Posted by Sideband

Take the control out completely (making a note of where everything goes) and you should find the switch will come off after straightening out the fixing tabs. A squirt of Servisol may well free up the contacts. Most times I've been able to sort these out with little effort. There isn't much current involved even taking the switch-on surge into account so unless something shorted (if there is a capacitor across the mains) then the switches don't really have a hard life.

You may not even need to remove the pot. If there is a gap between the three pot connections and the metal case, just squirt some Servisol in there and work the switch a few times and that should free up the sticky switch (if that is what the trouble is). You don't need to let it dry out (in fact Servisol shouldn't dry out completely as it leaves a lubricating film behind.

I agree up to a point, but not all switched pots are constructed the same. The 1M switched pot that I mentioned has a black plastic switch section which looks to be riveted to the pot body. I have often seen switches that can be removed by bending some tabs, but not all are like that.

Your suggestion that squirting Servisol into a slot where the three pot connections are is likely to clean/lube the potentiometer itself, rather than the switch, which is usually in a separate (though not sealed) section.

Problems with drilling a small hole in the switch section are (a) damaging the innards of the switch and (b) allowing swarf into the switch, both of which might just worsen the problem.

Colin.

vidjoman · 5th Oct 2019, 4:01 pm

Looks easy enough to take off the chassis as it has wires going to it. No need to even remove the wires. The photo seems to show the tabs that can be carefully bent back to get to the switch. Just make sure the switch goes back in the same position on the pot and check that the switch operates correctly before refixing the tabs.

27th Sep 2019, 10:07 pm	#1
hillmanie Pentode Join Date: May 2019 Location: Galway, Republic of Ireland. Posts: 208	Volume control Hi folks One of my fixer uppers came DOA as listed. On the face of it this might seem an easier fix, needing only to check the continuity, plug - cable - mains switch - transformer primary. Found first beak in the combined switch/volume control, double pole, the Live terminal. Looks the same as the ubiquitous ones of yesteryear. I seem to remember this as a common fault as I think the internal switch contacts were skinny and arced at ON and OFF. In those days being even more penny pinching than now I used to unclip the switch section and brighten the contacts. I may well do so again if they're not burned out as new same type replacements are seemingly unbtainable and an s/h eBay one is dear enough not to risk something could fail soon after. To continue the testing I thought of shorting out the offending pair with the precaution of swapping the live and neutral wires first so the Live remains switched. Does the forum think that this is too great a departure from safe practice even in the short term? I'm looking at another option to replace the two pots with smaller modern knurled types I see a-plenty, but thinks maybe they're battery only and won't take the 250v. Contacted an Eastern gentleman purveyor as to the specs on these but without result Any advice much thanked TT

28th Sep 2019, 6:22 pm	#2
ColinTheAmpMan1 Octode Join Date: Jan 2012 Location: Wimbledon, London, UK. Posts: 1,465	Re: Volume control If you let us all know what the item is (make, type) and what the specification of the switched pot is (apart from the 250VAC requirement. Resistance, log/lin) we might have a chance to rummage through our junk-boxes). A photo of the pot with some indication of physical dimensions would also be useful if you're wanting originality. You might be pleasantly surprised at what we might come up with, but we are just treading water so far. Colin.

28th Sep 2019, 6:41 pm	#3
John10b Nonode Join Date: Nov 2016 Location: Aberaeron, Ceredigion, Wales, UK. Posts: 2,887	Re: Volume control As Colin said you may be pleasantly surprised at what is available, take a look at Blore-ed.com, they may have just what you want. Cheers John

3rd Oct 2019, 10:32 pm	#6
hillmanie Pentode Join Date: May 2019 Location: Galway, Republic of Ireland. Posts: 208	Re: Volume control PS The recorder is a Ferguson 3218 Rgds TT

4th Oct 2019, 2:56 pm	#7
ColinTheAmpMan1 Octode Join Date: Jan 2012 Location: Wimbledon, London, UK. Posts: 1,465	Re: Volume control Could you provide a link to your photos in your album, please? I have no knowledge of the recorder that you mention, so I don't know what the value of the pot is supposed to be, either. The value will be stamped on the metal body of the pot somewhere, together with an "A" or "B" indication of the law. I have a switched 1M log pot which might be correct, as volume pots usually have a log law, but it only has a short (1cm) shaft with a "D" cross-section. It should be perfectly OK to short out the failed switch on the pot, so long as the LINE remains switched. It isn't ideal, of course, but it will function, even if electrical safety is marginally compromised. It is quite simple to append pictures to posts; check out the FAQ page for how to do it. Select "Reading and Posting Messages", followed by "Attachments and Images". Good Luck. Colin.

4th Oct 2019, 3:30 pm	#8
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Volume control The easiest way to add attachments (Pictures) to a post is to click the 'Go Advanced' box under the 'Quick Reply' box, then follow the instructions given therein.

4th Oct 2019, 3:37 pm	#9
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Volume control Or use the post reply button an the left which combines the two. Broad as long.

4th Oct 2019, 8:43 pm	#10
hillmanie Pentode Join Date: May 2019 Location: Galway, Republic of Ireland. Posts: 208	Re: Volume control Thank you Colin et al. Have confirmed the ID details (label is a bit unclear). On closer scrutiny It seems to read Ferguson 3218. Also re attachments I must be losing it as it's not rocket science. Heretofore I only read the Album instructions and on making access public. You're correct about the markings as when I loosed it I found on the back 8-4 1 megohm (the symbol) LIN (ear?) Looks like I've uploaded the two pics but they're not opening ? For the least disturbance I'll short the contact and switch the Live and get on with a few unfinished tasks not least of which is replacing the Philips liquified belt Rgds TT Attached Thumbnails

4th Oct 2019, 8:45 pm	#11
hillmanie Pentode Join Date: May 2019 Location: Galway, Republic of Ireland. Posts: 208	Re: Volume control Correction - thought the pics didn't render but I was wrong TT

5th Oct 2019, 7:39 am	#12
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,578	Re: Volume control Looks to be a perfectly normal 1 meg pot with switch. You can dismantle those quite easily. Take the control out completely (making a note of where everything goes) and you should find the switch will come off after straightening out the fixing tabs. A squirt of Servisol may well free up the contacts. Most times I've been able to sort these out with little effort. There isn't much current involved even taking the switch-on surge into account so unless something shorted (if there is a capacitor across the mains) then the switches don't really have a hard life. You may not even need to remove the pot. If there is a gap between the three pot connections and the metal case, just squirt some Servisol in there and work the switch a few times and that should free up the sticky switch (if that is what the trouble is). You don't need to let it dry out (in fact Servisol shouldn't dry out completely as it leaves a lubricating film behind. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman..... Last edited by Sideband; 5th Oct 2019 at 7:46 am.

5th Oct 2019, 1:52 pm	#13
hillmanie Pentode Join Date: May 2019 Location: Galway, Republic of Ireland. Posts: 208	Re: Volume control Thanks again. Not really a gap, which is why I previously mentioned I'd drill a small squirt hole. Re arcing, there's isn't a cap. across the contacts in this case TT

5th Oct 2019, 2:07 pm	#14
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Volume control I describe how I fixed the switch associated with a similar pot in this post:- https://www.vintage-radio.net/forum/...0&postcount=36 __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

5th Oct 2019, 4:01 pm	#16
vidjoman Dekatron Join Date: Jun 2013 Location: East Sussex, UK. Posts: 3,326	Re: Volume control Looks easy enough to take off the chassis as it has wires going to it. No need to even remove the wires. The photo seems to show the tabs that can be carefully bent back to get to the switch. Just make sure the switch goes back in the same position on the pot and check that the switch operates correctly before refixing the tabs.