Roberts R200 knobs stuck! - UK Vintage Radio Repair and Restoration Discussion Forum

JoshWard · 20th Jun 2012, 3:20 pm

Hi all,
I have found numerous threads regarding stuck knobs and have tried heating and penetrating fluid but to little avail.

I currently have a Roberts R200 on the bench which I need to get apart. All three knobs have rusty grub screws and all their heads have been sheared in the past. I cannot get a drill in there (or a junior hacksaw to cut the shafts) to drill the grub screws out, I have managed to get one knob off using heat but the other two are stuck fast.

Are there any other methods I could try?

If not I guess I will be spending all night in the workshop with a hot air gun and soldering iron

Thanks in advance,
Josh.

wireful3 · 20th Jun 2012, 5:11 pm

Josh, I assume you have left the penetrating fluid for ages. this seems to be important but if the screw heads are badly damaged it may not help.

I have a recollection of some time in the past getting the works out with the knobs in situ. I have no idea how I did this but it remains in my memory because I could not get it back in and that surprised me.

I probably used brute force along with lots of wriggling.

If you had considered cutting off the shafts with a junior hacksaw you could as a last resort use a nut-splitter approach instead and sacrifice the knobs. Obviously this is not much use unless you have replacement knobs.

JoshWard · 20th Jun 2012, 5:20 pm

Hi John,
I think I will have to go for the 'nut splitter' approach, and hope I can get another set of knobs. I will try gently drilling a hole in the centre of the knob to see if I can loosen it, or maybe a few small holes going across the top (all the knob brites are off now thanks to the hot air gun melting the glue!).

I have got nothing to lose as the knobs have got to come off to do anything with the set (I tried to get it out with the knobs on but to no avail!).

Josh.

davidgem1406 · 20th Jun 2012, 8:46 pm

As the knob brights are already off try drilling down through the top of the knob at the edge of the control shaft and in line with the grub screw. With luck this will drill away the contact point between grub screw and shaft and release the knob, without destroying either the knob or the control.

Dave

JoshWard · 26th Jun 2012, 4:42 pm

Hi Dave,
That's exactly what I did in the end and they all came off although sadly they fell apart in the process

Oh well they're off now and the chassis side of things are nearing completion. Now I've just got to find another set of knobs

Josh.

davidgem1406 · 26th Jun 2012, 10:10 pm

Hi Josh,
Shame about that but the knobs do seem to become very brittle. Finding another set may not be particularly easy, maybe a post under "Sets and Parts Wanted" my bear some fruit.
At least you have been able to get the chassis done, and I assume the cabinet.

Dave

JoshWard · 27th Jun 2012, 9:58 am

Hi Dave,
Yes I wonder if damp has anything to do with them becoming brittle and then hot/cold cycles over the years?
It's certainly been exposed to poor conditions as it has had some woodworm and of course the knobs were seized on by heavily rusted grub screws.

The chassis is performing well, cabinet is going to need a fair amount of work. Needs a new handle, catch, badge and recovering.

Josh.

Top Cap · 28th Jun 2012, 8:41 pm

Hi Josh, the R200 is worth saving if only for the fact it employs 'proper' transformers! They always seem to sound nicer than the complementary output stages with the audio stuffed through a capacitor. The knobs, ah yes, these used to be as common as muck, even Radiospares (as they were then) sold them. I would like to think that your search for these may prove to be fruitful. They used to crop up on Premier kit radios etc., so keep a good look out. This radio harks from the days when Roberts actually made their radios rather than Mullard! If you catch my drift

... Happy hunting, will keep a vigil also!

JoshWard · 29th Jun 2012, 12:59 pm

Hi Les,
Yes not putting the audio through a transformer is never quite 'right' to me although I have seen some very expensive valve Hi-Fi gear with direct coupling. I have always seen a lack of a transformer as a cost cutting measure rather than a desire to reduce component count in a signal path as some seem to see it!
Thanks to Brian Pateman I now have a set on their way. Now I just need to finish sanding back the cabinet, get a few trim parts from Roberts then it's all ready for recovering!

Josh.

20th Jun 2012, 3:20 pm	#1
JoshWard Octode Join Date: Dec 2005 Location: Near Stowmarket, Suffolk, UK. Posts: 1,962	Roberts R200 knobs stuck! Hi all, I have found numerous threads regarding stuck knobs and have tried heating and penetrating fluid but to little avail. I currently have a Roberts R200 on the bench which I need to get apart. All three knobs have rusty grub screws and all their heads have been sheared in the past. I cannot get a drill in there (or a junior hacksaw to cut the shafts) to drill the grub screws out, I have managed to get one knob off using heat but the other two are stuck fast. Are there any other methods I could try? If not I guess I will be spending all night in the workshop with a hot air gun and soldering iron Thanks in advance, Josh.

20th Jun 2012, 5:11 pm	#2
wireful3 Retired Dormant Member Join Date: Sep 2003 Location: Bristol, UK. Posts: 808	Re: Roberts R200 knobs stuck! Josh, I assume you have left the penetrating fluid for ages. this seems to be important but if the screw heads are badly damaged it may not help. I have a recollection of some time in the past getting the works out with the knobs in situ. I have no idea how I did this but it remains in my memory because I could not get it back in and that surprised me. I probably used brute force along with lots of wriggling. If you had considered cutting off the shafts with a junior hacksaw you could as a last resort use a nut-splitter approach instead and sacrifice the knobs. Obviously this is not much use unless you have replacement knobs.

20th Jun 2012, 5:20 pm	#3
JoshWard Octode Join Date: Dec 2005 Location: Near Stowmarket, Suffolk, UK. Posts: 1,962	Re: Roberts R200 knobs stuck! Hi John, I think I will have to go for the 'nut splitter' approach, and hope I can get another set of knobs. I will try gently drilling a hole in the centre of the knob to see if I can loosen it, or maybe a few small holes going across the top (all the knob brites are off now thanks to the hot air gun melting the glue!). I have got nothing to lose as the knobs have got to come off to do anything with the set (I tried to get it out with the knobs on but to no avail!). Josh.

20th Jun 2012, 8:46 pm	#4
davidgem1406 Heptode Join Date: Feb 2011 Location: Sheerness, Kent, UK. Posts: 936	Re: Roberts R200 knobs stuck! As the knob brights are already off try drilling down through the top of the knob at the edge of the control shaft and in line with the grub screw. With luck this will drill away the contact point between grub screw and shaft and release the knob, without destroying either the knob or the control. Dave

26th Jun 2012, 4:42 pm	#5
JoshWard Octode Join Date: Dec 2005 Location: Near Stowmarket, Suffolk, UK. Posts: 1,962	Re: Roberts R200 knobs stuck! Hi Dave, That's exactly what I did in the end and they all came off although sadly they fell apart in the process Oh well they're off now and the chassis side of things are nearing completion. Now I've just got to find another set of knobs Josh.

26th Jun 2012, 10:10 pm	#6
davidgem1406 Heptode Join Date: Feb 2011 Location: Sheerness, Kent, UK. Posts: 936	Re: Roberts R200 knobs stuck! Hi Josh, Shame about that but the knobs do seem to become very brittle. Finding another set may not be particularly easy, maybe a post under "Sets and Parts Wanted" my bear some fruit. At least you have been able to get the chassis done, and I assume the cabinet. Dave

27th Jun 2012, 9:58 am	#7
JoshWard Octode Join Date: Dec 2005 Location: Near Stowmarket, Suffolk, UK. Posts: 1,962	Re: Roberts R200 knobs stuck! Hi Dave, Yes I wonder if damp has anything to do with them becoming brittle and then hot/cold cycles over the years? It's certainly been exposed to poor conditions as it has had some woodworm and of course the knobs were seized on by heavily rusted grub screws. The chassis is performing well, cabinet is going to need a fair amount of work. Needs a new handle, catch, badge and recovering. Josh.

28th Jun 2012, 8:41 pm	#8
Top Cap Octode Join Date: Mar 2006 Location: Watford, Hertfordshire, UK. Posts: 1,270	Re: Roberts R200 knobs stuck! Hi Josh, the R200 is worth saving if only for the fact it employs 'proper' transformers! They always seem to sound nicer than the complementary output stages with the audio stuffed through a capacitor. The knobs, ah yes, these used to be as common as muck, even Radiospares (as they were then) sold them. I would like to think that your search for these may prove to be fruitful. They used to crop up on Premier kit radios etc., so keep a good look out. This radio harks from the days when Roberts actually made their radios rather than Mullard! If you catch my drift ... Happy hunting, will keep a vigil also! __________________ Whether the Top Cap is Grid or Anode - touching it will give you a buzz either way! Last edited by Top Cap; 28th Jun 2012 at 8:42 pm. Reason: typo

29th Jun 2012, 12:59 pm	#9
JoshWard Octode Join Date: Dec 2005 Location: Near Stowmarket, Suffolk, UK. Posts: 1,962	Re: Roberts R200 knobs stuck! Hi Les, Yes not putting the audio through a transformer is never quite 'right' to me although I have seen some very expensive valve Hi-Fi gear with direct coupling. I have always seen a lack of a transformer as a cost cutting measure rather than a desire to reduce component count in a signal path as some seem to see it! Thanks to Brian Pateman I now have a set on their way. Now I just need to finish sanding back the cabinet, get a few trim parts from Roberts then it's all ready for recovering! Josh.