RAP 646 Radio UK - UK Vintage Radio Repair and Restoration Discussion Forum

Vecher1 · 1st Apr 2021, 7:26 pm

All, Just purchased a RAP 646 I think.. No model number on back .. Its 5 tubes..
I am located in the US.. My question is How do you remove the tuning knobs?

Cannot figure that out.. Pictures to follow as I get them taken..

Thanks

Skip

paulsherwin · 1st Apr 2021, 7:46 pm

Can you clarify what this radio actually is? We can't help you otherwise. 'RAF 646' means nothing to me or to Google.

slidertogrid · 1st Apr 2021, 8:02 pm

Is It a RAP 646 ? If so the knobs are held on with grub screws, the tuning knob has a slot to access the screw but you have to line the screw up by turning the knob.

slidertogrid · 1st Apr 2021, 8:11 pm

Some pictures to clarify.

Cobaltblue · 1st Apr 2021, 8:16 pm

I have updated the title assuming it is an RAP

Cheers

Mike T

paulsherwin · 1st Apr 2021, 8:20 pm

Thanks Mike. Nice radio, Radiomuseum page: https://www.radiomuseum.org/r/rap_646.html

Vecher1 · 1st Apr 2021, 8:31 pm

YUP Here are some pictures..

[img]https://***********************/65535/51089142080_618ed2bf7a_c.jpg[/img]

[img]https://***********************/65535/51088402654_bc50cfef34_c.jpg[/img]

[img]https://***********************/65535/51088402534_3d23d86967_c.jpg[/img]

Skip

Nickthedentist · 1st Apr 2021, 9:38 pm

Doesn't the centre cap unscrew, clockwise ISTR?

Vecher1 · 1st Apr 2021, 10:10 pm

Ok was able to get knobs off All it took was loosen the set screws and pull them off.. Actually very easy

Skip

McMurdo · 2nd Apr 2021, 1:53 am

Beautiful radio, and in my neck of the woods they're rather sought after!

Radio Wrangler · 2nd Apr 2021, 2:18 am

It looks like a restyled version of the 'Muirhead' slow motion drive.

If so, the little ivory button in the middle of the knob can be grasped and unscrewed anti-clockwise with respect to the slow motion knob, and the slow motion knob will come off. You should then be able to see the workings. Loosening the grub screw via that little notch close to the panel with the thing in the correct alignment should bring the whole thing off.

Bakelite and irreplaceable, so don't drop!

David

vinrads · 2nd Apr 2021, 9:12 am

I don't remember the centre screw unscrewing, it is part of the thumb wheel it's just one unit you can see the workings once you have remover the knob, nice radio does yours have the push pull output?

Mick.

Vecher1 · 2nd Apr 2021, 9:36 pm

No. It's just 5 tubes.

Skip

paulsherwin · 2nd Apr 2021, 10:16 pm

The same model seems to have been produced in several different configurations. There was one with a tuned RF stage and one with push-pull 6V6s doing the output.

mark pirate · 3rd Apr 2021, 8:09 am

RAP used a modular chassis in a lot of models, it was a case of adding chassis sections according to the specification.
I had the large console model with push-pull 6v6 output stage, a very impressive set, but sadly the cabinet had suffered a lot of veneer loss, so was passed on to a friend who had the skills to repair the cabinet.

Mark

Vecher1 · 24th Apr 2021, 5:00 am

OK. Just started to get to this one. Took out of cabinet. Looked underneath.

Not what I expected. Lots of caps.

Before I start has anyone done a recap on this model? Anything I should know before proceeding?

Thanks, Skip.

lloydwells · 25th Apr 2021, 10:33 am

I have the console version of this to remove the tuning knob loosen the grub screw accessible through the gap in the side of the back part of the knob and pull the whole thing forwards it's two controls but all one unit easy sets to restore it'll be full of metal case paper in oil caps that rarely go wrong

Vecher1 · 12th May 2021, 2:52 pm

All, Ok started to recap.. I will take some pictures soon.. I did notice one thing.. On the volume control it has a series of resistors and a wiper on back.. never seen anything like that.. the schematic say it has 14 resistors Mine only has 12? But it looks factory..

Anyone run across this? PS the chassis really shines up nice.. Love that chrome..

Not sure on how to post pictures here..

Skip

Vecher1 · 14th Jul 2021, 11:14 pm

ALL, Does anyone have any alignment instructions for this??

Skip

cathoderay57 · 15th Jul 2021, 8:27 am

Hi Skip, I'm assuming that you have got the manufacturer's service data sheet already? However, it gives the alignment frequencies but not the procedure. Since yours is the simpler version without the RF amplifier I could probably draft up something if it would help and if nobody else can come up with one? The manufacturer's circuit doesn't provide component numbers for the coils and trimmers though, and so I'd have to do screen grabs to show which was which. I don't think that would breaking any Forum rules. Cheers, Jerry

1st Apr 2021, 7:26 pm	#1
Vecher1 Triode Join Date: Apr 2021 Location: Lansdale, Pennslyvania, USA Posts: 46	RAP 646 Radio UK All, Just purchased a RAP 646 I think.. No model number on back .. Its 5 tubes.. I am located in the US.. My question is How do you remove the tuning knobs? Cannot figure that out.. Pictures to follow as I get them taken.. Thanks Skip Last edited by Cobaltblue; 1st Apr 2021 at 8:15 pm. Reason: Updated title to RAP

1st Apr 2021, 7:46 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: RAF 646 Radio UK Can you clarify what this radio actually is? We can't help you otherwise. 'RAF 646' means nothing to me or to Google.

1st Apr 2021, 8:02 pm	#3
slidertogrid Octode Join Date: Apr 2005 Location: Peterborough, Cambridgeshire, UK. Posts: 1,898	Re: RAF 646 Radio UK Is It a RAP 646 ? If so the knobs are held on with grub screws, the tuning knob has a slot to access the screw but you have to line the screw up by turning the knob. Last edited by slidertogrid; 1st Apr 2021 at 8:13 pm.

1st Apr 2021, 8:11 pm	#4
slidertogrid Octode Join Date: Apr 2005 Location: Peterborough, Cambridgeshire, UK. Posts: 1,898	Re: RAF 646 Radio UK Some pictures to clarify. Attached Thumbnails

1st Apr 2021, 8:16 pm	#5
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,866	Re: RAP 646 Radio UK I have updated the title assuming it is an RAP Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

1st Apr 2021, 8:20 pm	#6
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: RAP 646 Radio UK Thanks Mike. Nice radio, Radiomuseum page: https://www.radiomuseum.org/r/rap_646.html

1st Apr 2021, 8:31 pm	#7
Vecher1 Triode Join Date: Apr 2021 Location: Lansdale, Pennslyvania, USA Posts: 46	Re: RAP 646 Radio UK YUP Here are some pictures.. [img]https://*********************/65535/51089142080_618ed2bf7a_c.jpg[/img] [img]https://*******************/65535/51088402654_bc50cfef34_c.jpg[/img] [img]https://*********************/65535/51088402534_3d23d86967_c.jpg[/img] Skip

1st Apr 2021, 9:38 pm	#8
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,846	Re: RAP 646 Radio UK Doesn't the centre cap unscrew, clockwise ISTR?

1st Apr 2021, 10:10 pm	#9
Vecher1 Triode Join Date: Apr 2021 Location: Lansdale, Pennslyvania, USA Posts: 46	Re: RAP 646 Radio UK Ok was able to get knobs off All it took was loosen the set screws and pull them off.. Actually very easy Skip

2nd Apr 2021, 1:53 am	#10
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,271	Re: RAP 646 Radio UK Beautiful radio, and in my neck of the woods they're rather sought after! __________________ Kevin

2nd Apr 2021, 2:18 am	#11
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,877	Re: RAP 646 Radio UK It looks like a restyled version of the 'Muirhead' slow motion drive. If so, the little ivory button in the middle of the knob can be grasped and unscrewed anti-clockwise with respect to the slow motion knob, and the slow motion knob will come off. You should then be able to see the workings. Loosening the grub screw via that little notch close to the panel with the thing in the correct alignment should bring the whole thing off. Bakelite and irreplaceable, so don't drop! David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

2nd Apr 2021, 9:12 am	#12
vinrads Dekatron Join Date: Feb 2009 Location: Chesterfield, Derbyshire, UK. Posts: 3,762	Re: RAP 646 Radio UK I don't remember the centre screw unscrewing, it is part of the thumb wheel it's just one unit you can see the workings once you have remover the knob, nice radio does yours have the push pull output? Mick.

2nd Apr 2021, 9:36 pm	#13
Vecher1 Triode Join Date: Apr 2021 Location: Lansdale, Pennslyvania, USA Posts: 46	Re: RAP 646 Radio UK No. It's just 5 tubes. Skip

2nd Apr 2021, 10:16 pm	#14
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: RAP 646 Radio UK The same model seems to have been produced in several different configurations. There was one with a tuned RF stage and one with push-pull 6V6s doing the output.

3rd Apr 2021, 8:09 am	#15
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: RAP 646 Radio UK RAP used a modular chassis in a lot of models, it was a case of adding chassis sections according to the specification. I had the large console model with push-pull 6v6 output stage, a very impressive set, but sadly the cabinet had suffered a lot of veneer loss, so was passed on to a friend who had the skills to repair the cabinet. Mark

24th Apr 2021, 5:00 am	#16
Vecher1 Triode Join Date: Apr 2021 Location: Lansdale, Pennslyvania, USA Posts: 46	Re: RAP 646 Radio UK OK. Just started to get to this one. Took out of cabinet. Looked underneath. Not what I expected. Lots of caps. Before I start has anyone done a recap on this model? Anything I should know before proceeding? Thanks, Skip.

25th Apr 2021, 10:33 am	#17
lloydwells Heptode Join Date: Aug 2016 Location: Dumfries, Scotland, UK. Posts: 549	Re: RAP 646 Radio UK I have the console version of this to remove the tuning knob loosen the grub screw accessible through the gap in the side of the back part of the knob and pull the whole thing forwards it's two controls but all one unit easy sets to restore it'll be full of metal case paper in oil caps that rarely go wrong

12th May 2021, 2:52 pm	#18
Vecher1 Triode Join Date: Apr 2021 Location: Lansdale, Pennslyvania, USA Posts: 46	Re: RAP 646 Radio UK All, Ok started to recap.. I will take some pictures soon.. I did notice one thing.. On the volume control it has a series of resistors and a wiper on back.. never seen anything like that.. the schematic say it has 14 resistors Mine only has 12? But it looks factory.. Anyone run across this? PS the chassis really shines up nice.. Love that chrome.. Not sure on how to post pictures here.. Skip

14th Jul 2021, 11:14 pm	#19
Vecher1 Triode Join Date: Apr 2021 Location: Lansdale, Pennslyvania, USA Posts: 46	Re: RAP 646 Radio UK ALL, Does anyone have any alignment instructions for this?? Skip

15th Jul 2021, 8:27 am	#20
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,384	Re: RAP 646 Radio UK Hi Skip, I'm assuming that you have got the manufacturer's service data sheet already? However, it gives the alignment frequencies but not the procedure. Since yours is the simpler version without the RF amplifier I could probably draft up something if it would help and if nobody else can come up with one? The manufacturer's circuit doesn't provide component numbers for the coils and trimmers though, and so I'd have to do screen grabs to show which was which. I don't think that would breaking any Forum rules. Cheers, Jerry