Replacing the mounting of EM84 magic eye - UK Vintage Radio Repair and Restoration Discussion Forum

brightsparkey · 16th Feb 2018, 2:56 pm

I have a radio with an EM84 tuning indicator. The indicator is not very bright, although it does function, and I wondered about replacing it as I already have one (from my bass amp project..that's another story..). However, the original is mounted in some sort of rubber mounting, and the material is in a poor state - I really suspect that it will totally disintegrate if I try to remove the old tube as bits of it have been falling off as I've been working on the chassis.

Is there a supply of these mounts from somewhere, or are they specially designed by the radio manufacturer? The set is a SABA freudenstadt, btw.

Any advice welcome.

Kevin.

paulsherwin · 16th Feb 2018, 3:04 pm

You can probably fabricate something or use a cable tie. EM84s don't run very hot.

Tractionist · 16th Feb 2018, 4:29 pm

You could try to 'stabilise' the original mount using Rust-O-leum 'Rubber Paint' i.e. prior to [and after] removing the defective valve?

Boater Sam · 17th Feb 2018, 4:00 am

Toss it and wrap the valve with self amalgamating tape.

Ed_Dinning · 17th Feb 2018, 9:39 am

Hi Kevin, if no luck PM me and I'll see what I can find in a week or so.

Ed

David G4EBT · 17th Feb 2018, 10:21 am

At least the EM84 (AKA 6E2) itself is cheap if you do need one - expect to pay a fiver from the Ukraine or two for a fiver from Hong Kong (plus post).

An EM84 driver kit for a VU meter, with PCB, valve and other bits is typically under £7.00 post free from H.K.

EM84 brings back memories of Grundig reel-to-reel tape recorders from the mid to late 50s.

As to the rubber mountings, it might help if you posted a picture Kevin.

Edward Huggins · 17th Feb 2018, 11:11 am

These EM84s seemed such an advance over the previous EM80 series. It was easy to use and one could readily see the overlap where there was too much gain/overload. My goodness, I thought these were really sophisticated at the time!

brightsparkey · 18th Feb 2018, 12:02 am

Thanks for the suggestions. I'll take some photos on Monday when I'm back with the set.

Kevin

Radio1950 · 18th Feb 2018, 8:48 am

Ahoy there!
Boater Sam has a great idea in Post #4.
Anchors aweigh!

mke

brightsparkey · 20th Feb 2018, 8:35 pm

Investigated the magic eye - point of no return reached

Removed the clip that holds the front glass - can then see that the tube is held in a clip on a plate that can be removed. The degraded material looks like some sort of foam or rubber that has gone brittle.

Removed the plate + tube and most of the foam came to pieces, revealing a plastic window that the foam is there to hold in front of the tube.

The eye looks dirty but in fact its like that on the inside (cleaning makes no odd.), so the phosphor is definately worn. I guess it spends all its working life tuned in and closed..

Removed the tube from the clip. Steel clip is adequate on its own to hold the tube itself, but the bezel will need securing somehow. Cable ties a possibility, but would be ugly. Some sort of adhesive which is temperature stable and reversible?

It turns out I have a 6E2 valve (cheap chinese) which is not quite the same characteristic as the 6E3 or EM84 (6E2==EM87) - the eye closure graph is quite different, so I'm looking at getting an NOS russian EM84, so a bit of time to work out how to solve the mounting issue.

Kevin.

brightsparkey · 13th Mar 2018, 3:13 pm

Having replaced the tube, my solution was to cut some rubber sheet used for airconditioning ducts into a rectangle with an aperture for the plastic bezel. I needed two sheets to get enough thickness. They were glued together with contact adhesive and wrapped around the tube before clipping into the holder.

The problem with this arrangement is aligning the phosphor with the aperture and the opening in the front glass - too many degrees of freedom - very fiddly, and the rubber is not inclined to move once in the clip.

After all this, the line on the tube is still at an angle even after using all the slack in the mounting screw - I suspect the actual tube is not straight inside - maybe it was a reject tube.. you can never tell their history. The replacement was a Mullard NOS tube and clearly unused.

Kevin.

Boater Sam · 13th Mar 2018, 3:24 pm

The phosphor strip is always at an angle in the tube.

brightsparkey · 13th Mar 2018, 4:31 pm

I guess it's the way of things, as usual

As far as self-amalg goes - I always find that it prefers to amalgamate anywhere but where I want it to be..

Kevin.

16th Feb 2018, 2:56 pm	#1
brightsparkey Pentode Join Date: Sep 2017 Location: Cambridge, Cambridgeshire, UK. Posts: 148	Replacing the mounting of EM84 magic eye I have a radio with an EM84 tuning indicator. The indicator is not very bright, although it does function, and I wondered about replacing it as I already have one (from my bass amp project..that's another story..). However, the original is mounted in some sort of rubber mounting, and the material is in a poor state - I really suspect that it will totally disintegrate if I try to remove the old tube as bits of it have been falling off as I've been working on the chassis. Is there a supply of these mounts from somewhere, or are they specially designed by the radio manufacturer? The set is a SABA freudenstadt, btw. Any advice welcome. Kevin.

16th Feb 2018, 3:04 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: Replacing the mounting of EM84 magic eye You can probably fabricate something or use a cable tie. EM84s don't run very hot.

16th Feb 2018, 4:29 pm	#3
Tractionist Heptode Join Date: Apr 2016 Location: Cheltenham, Gloucestershire, UK. Posts: 875	Re: Replacing the mounting of EM84 magic eye You could try to 'stabilise' the original mount using Rust-O-leum 'Rubber Paint' i.e. prior to [and after] removing the defective valve? __________________ Red to red, black to black. Throw the switch and stand well back!

17th Feb 2018, 9:39 am	#5
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Replacing the mounting of EM84 magic eye Hi Kevin, if no luck PM me and I'll see what I can find in a week or so. Ed

17th Feb 2018, 10:21 am	#6
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,761	Re: Replacing the mounting of EM84 magic eye At least the EM84 (AKA 6E2) itself is cheap if you do need one - expect to pay a fiver from the Ukraine or two for a fiver from Hong Kong (plus post). An EM84 driver kit for a VU meter, with PCB, valve and other bits is typically under £7.00 post free from H.K. EM84 brings back memories of Grundig reel-to-reel tape recorders from the mid to late 50s. As to the rubber mountings, it might help if you posted a picture Kevin. __________________ David. BVWS Member. G-QRP Club member 1339.

17th Feb 2018, 4:00 am	#4
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Replacing the mounting of EM84 magic eye Toss it and wrap the valve with self amalgamating tape.

17th Feb 2018, 11:11 am	#7
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,328	Re: Replacing the mounting of EM84 magic eye These EM84s seemed such an advance over the previous EM80 series. It was easy to use and one could readily see the overlap where there was too much gain/overload. My goodness, I thought these were really sophisticated at the time! __________________ Edward.

18th Feb 2018, 12:02 am	#8
brightsparkey Pentode Join Date: Sep 2017 Location: Cambridge, Cambridgeshire, UK. Posts: 148	Re: Replacing the mounting of EM84 magic eye Thanks for the suggestions. I'll take some photos on Monday when I'm back with the set. Kevin

18th Feb 2018, 8:48 am	#9
Radio1950 Hexode Join Date: Apr 2017 Location: Buderim, Queensland, Australia. Posts: 428	Re: Replacing the mounting of EM84 magic eye Ahoy there! Boater Sam has a great idea in Post #4. Anchors aweigh! mke

20th Feb 2018, 8:35 pm	#10
brightsparkey Pentode Join Date: Sep 2017 Location: Cambridge, Cambridgeshire, UK. Posts: 148	Re: Replacing the mounting of EM84 magic eye Investigated the magic eye - point of no return reached Removed the clip that holds the front glass - can then see that the tube is held in a clip on a plate that can be removed. The degraded material looks like some sort of foam or rubber that has gone brittle. Removed the plate + tube and most of the foam came to pieces, revealing a plastic window that the foam is there to hold in front of the tube. The eye looks dirty but in fact its like that on the inside (cleaning makes no odd.), so the phosphor is definately worn. I guess it spends all its working life tuned in and closed.. Removed the tube from the clip. Steel clip is adequate on its own to hold the tube itself, but the bezel will need securing somehow. Cable ties a possibility, but would be ugly. Some sort of adhesive which is temperature stable and reversible? It turns out I have a 6E2 valve (cheap chinese) which is not quite the same characteristic as the 6E3 or EM84 (6E2==EM87) - the eye closure graph is quite different, so I'm looking at getting an NOS russian EM84, so a bit of time to work out how to solve the mounting issue. Kevin. Attached Thumbnails

13th Mar 2018, 3:13 pm	#11
brightsparkey Pentode Join Date: Sep 2017 Location: Cambridge, Cambridgeshire, UK. Posts: 148	Re: Replacing the mounting of EM84 magic eye Having replaced the tube, my solution was to cut some rubber sheet used for airconditioning ducts into a rectangle with an aperture for the plastic bezel. I needed two sheets to get enough thickness. They were glued together with contact adhesive and wrapped around the tube before clipping into the holder. The problem with this arrangement is aligning the phosphor with the aperture and the opening in the front glass - too many degrees of freedom - very fiddly, and the rubber is not inclined to move once in the clip. After all this, the line on the tube is still at an angle even after using all the slack in the mounting screw - I suspect the actual tube is not straight inside - maybe it was a reject tube.. you can never tell their history. The replacement was a Mullard NOS tube and clearly unused. Kevin.

13th Mar 2018, 3:24 pm	#12
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Replacing the mounting of EM84 magic eye The phosphor strip is always at an angle in the tube.

13th Mar 2018, 4:31 pm	#13
brightsparkey Pentode Join Date: Sep 2017 Location: Cambridge, Cambridgeshire, UK. Posts: 148	Re: Replacing the mounting of EM84 magic eye I guess it's the way of things, as usual As far as self-amalg goes - I always find that it prefers to amalgamate anywhere but where I want it to be.. Kevin.