Roberts R505 volume - UK Vintage Radio Repair and Restoration Discussion Forum

Martin Bush · 21st Jan 2016, 1:15 pm

Hi

I am trying to do what should be a minor job of cleaning the volume switch on my Roberts r505.

However despite a bucket load of servisol and twiddling I'm not making any improvement.

The switch is not noisy. What happens is you turn it through three quarters and the volume remains almost constant. The. Towards the top end it jumps up to full whack.

Any ideas? Is it a case of replacing the pot? I did post about this a while ago and have had a really good go at the pot, but I fear it will use all my switch cleaner and be no better.

I have attached a photo in case anyone thinks they can spot anything...

Martin

paulsherwin · 21st Jan 2016, 1:21 pm

The carbon track is probably cracked. If you can get access, try rubbing the track with a soft pencil.

Replacement is the best solution, but it may be difficult to find a suitable pot.

Martin Bush · 21st Jan 2016, 1:27 pm

Thanks Paul.

I it is quite a compact pot and held together with tiny rivets. I've no hope of getting in.

Silly question... Can I swap it for the tone pot?

paulsherwin · 21st Jan 2016, 1:43 pm

Can you drill the rivets out?

I don't think the two pots are interchangeable, though I don't have a circuit handy.

Martin Bush · 21st Jan 2016, 1:47 pm

I could but I doubt my capabilities to reassemble it later.

I will seek the circuit and probably look for a replacement pot ultimately.

Martin Bush · 21st Jan 2016, 1:52 pm

The circuit appears to say that they are both 100k log. They look the same...

paulsherwin · 21st Jan 2016, 1:55 pm

If that is true then you can indeed swap them over, but a log law pot is unusual for a tone control. No harm in trying though.

Martin Bush · 21st Jan 2016, 2:14 pm

I'll give it a go and report back.

60 oldjohn · 21st Jan 2016, 2:18 pm

If you swap them and volume seems to be all at one end of adjustment you could add a 47k resistor from slider to earthy end of pot, then it should act as the original Log pot.

John.

Martin Bush · 21st Jan 2016, 2:31 pm

Thanks John. I will give it a go. Just need to root out a resistor first

60 oldjohn · 21st Jan 2016, 2:55 pm

Try without first it may sound ok. Any resistance from 40k to 60k will do. The resistor needs to be around half the track resistance to change a Lin pot into a Log mounted between slider to earthy end of track. As you know you can make you own resistance eg two 120k resistors in parallel, use whatever you have.

John.

Martin Bush · 21st Jan 2016, 3:58 pm

Well, would you believe it, it worked...

It was a ****** to do due to how it had been soldered and twisted together, but I managed it.

I am amazed...

I do feel a bit like The Phantom now...

Herald1360 · 21st Jan 2016, 6:11 pm

I'd certainly believe it worked; congratulations on doing it successfully!

paulsherwin · 21st Jan 2016, 6:15 pm

A perfectly acceptable repair given the absence of an easily available replacement pot - not a bodge at all.

sobell1980 · 21st Jan 2016, 7:13 pm

Well done Martin. You definately need to have more faith in yourself. Great repair job. Onto the next project now!
Another wireless saved from the dump and lives on. Do you use all your radios Martin? Congratulations with the repair.
Dave.

Martin Bush · 21st Jan 2016, 7:57 pm

Thanks everyone. This one is a nice set with just one fault. I think its time to dig out a non worker now and see what I can do.

I find Roberts sets easy to take apart at least...

Do i use them all... ? I try! My other half is very much one for listening to the radio via freeview or phone, so theres little demand for real radio in our house. So when I get chance I get out as many sets as I have batteries for and give them a blast.

I sense another thread coming on...

21st Jan 2016, 1:15 pm	#1
Martin Bush Octode Join Date: Jan 2015 Location: Oxfordshire, UK. Posts: 1,911	Roberts R505 volume Hi I am trying to do what should be a minor job of cleaning the volume switch on my Roberts r505. However despite a bucket load of servisol and twiddling I'm not making any improvement. The switch is not noisy. What happens is you turn it through three quarters and the volume remains almost constant. The. Towards the top end it jumps up to full whack. Any ideas? Is it a case of replacing the pot? I did post about this a while ago and have had a really good go at the pot, but I fear it will use all my switch cleaner and be no better. I have attached a photo in case anyone thinks they can spot anything... Martin Attached Thumbnails

21st Jan 2016, 1:21 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,967	Re: Roberts r505 volume The carbon track is probably cracked. If you can get access, try rubbing the track with a soft pencil. Replacement is the best solution, but it may be difficult to find a suitable pot.

21st Jan 2016, 1:27 pm	#3
Martin Bush Octode Join Date: Jan 2015 Location: Oxfordshire, UK. Posts: 1,911	Re: Roberts r505 volume Thanks Paul. I it is quite a compact pot and held together with tiny rivets. I've no hope of getting in. Silly question... Can I swap it for the tone pot?

21st Jan 2016, 1:43 pm	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,967	Re: Roberts r505 volume Can you drill the rivets out? I don't think the two pots are interchangeable, though I don't have a circuit handy.

21st Jan 2016, 1:47 pm	#5
Martin Bush Octode Join Date: Jan 2015 Location: Oxfordshire, UK. Posts: 1,911	Re: Roberts r505 volume I could but I doubt my capabilities to reassemble it later. I will seek the circuit and probably look for a replacement pot ultimately.

21st Jan 2016, 1:52 pm	#6
Martin Bush Octode Join Date: Jan 2015 Location: Oxfordshire, UK. Posts: 1,911	Re: Roberts r505 volume The circuit appears to say that they are both 100k log. They look the same...

21st Jan 2016, 1:55 pm	#7
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,967	Re: Roberts r505 volume If that is true then you can indeed swap them over, but a log law pot is unusual for a tone control. No harm in trying though.

21st Jan 2016, 2:14 pm	#8
Martin Bush Octode Join Date: Jan 2015 Location: Oxfordshire, UK. Posts: 1,911	Re: Roberts R505 volume I'll give it a go and report back.

21st Jan 2016, 2:18 pm	#9
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Re: Roberts R505 volume If you swap them and volume seems to be all at one end of adjustment you could add a 47k resistor from slider to earthy end of pot, then it should act as the original Log pot. John.

21st Jan 2016, 2:31 pm	#10
Martin Bush Octode Join Date: Jan 2015 Location: Oxfordshire, UK. Posts: 1,911	Re: Roberts R505 volume Thanks John. I will give it a go. Just need to root out a resistor first

21st Jan 2016, 2:55 pm	#11
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Re: Roberts R505 volume Try without first it may sound ok. Any resistance from 40k to 60k will do. The resistor needs to be around half the track resistance to change a Lin pot into a Log mounted between slider to earthy end of track. As you know you can make you own resistance eg two 120k resistors in parallel, use whatever you have. John.

21st Jan 2016, 3:58 pm	#12
Martin Bush Octode Join Date: Jan 2015 Location: Oxfordshire, UK. Posts: 1,911	Re: Roberts R505 volume Well, would you believe it, it worked... It was a ****** to do due to how it had been soldered and twisted together, but I managed it. I am amazed... I do feel a bit like The Phantom now...

21st Jan 2016, 6:11 pm	#13
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Roberts R505 volume I'd certainly believe it worked; congratulations on doing it successfully! __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

21st Jan 2016, 6:15 pm	#14
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,967	Re: Roberts R505 volume A perfectly acceptable repair given the absence of an easily available replacement pot - not a bodge at all.

21st Jan 2016, 7:13 pm	#15
sobell1980 Octode Join Date: May 2011 Location: Bromyard, Herefordshire, UK. Posts: 1,241	Re: Roberts R505 volume Well done Martin. You definately need to have more faith in yourself. Great repair job. Onto the next project now! Another wireless saved from the dump and lives on. Do you use all your radios Martin? Congratulations with the repair. Dave.

21st Jan 2016, 7:57 pm	#16
Martin Bush Octode Join Date: Jan 2015 Location: Oxfordshire, UK. Posts: 1,911	Re: Roberts R505 volume Thanks everyone. This one is a nice set with just one fault. I think its time to dig out a non worker now and see what I can do. I find Roberts sets easy to take apart at least... Do i use them all... ? I try! My other half is very much one for listening to the radio via freeview or phone, so theres little demand for real radio in our house. So when I get chance I get out as many sets as I have batteries for and give them a blast. I sense another thread coming on...