Magic Eyes - UK Vintage Radio Repair and Restoration Discussion Forum

david3006 · 20th Jan 2012, 1:19 pm

I know little about these items, has anyone posted a beginners guide to Magic Eyes?

I have several sets with dead MEs and have replaced one which now works. However to avoid changing one that may be OK but associated circuits may be duff, I would like an explanation of how they are set up so that I can make up a tester.

Any offers from a genius out there please!

David

PS the info may be a good thing to put up on a sticky.

Pete_kaye · 20th Jan 2012, 1:47 pm

There was link to someone who ran a website in U.S. just on this topic and included useful info and different moving images of different types of ME.

I cannot locate it right now. Google it?

SeanStevens · 20th Jan 2012, 2:08 pm

http://www.magiceyetubes.com/

??

SEAN

HamishBoxer · 20th Jan 2012, 2:42 pm

Another good site,like the test gear with four magiceyes fitted!

David

paulsherwin · 20th Jan 2012, 3:13 pm

If you want to build a tester, just take a circuit from a radio. To check deflection apply some volts to the grid (pin 4 for an EM34) - a PP3 battery will be fine. The vast majority of magic eyes fail because the fluorescent phosphor wears out - if the valve has heater and HT voltage applied and is not glowing green, this is probably the explanation. You can usually see a very faint glow from a tired magic eye if you look at it in a darkened room.

It's easy enough to test these valves in circuit. Just check all the voltages are there using a DMM. If the voltages are correct but the valve is dim or dead, it's gone to the big stockroom in the sky.

Never buy a used magic eye unless you know and trust the seller or can see it working yourself. Anything described as 'untested' is likely to be bad.

Miguel Lopez · 20th Jan 2012, 5:16 pm

And what would be the expected lifetime for magic eyes?

I pretend to put one of them (TESLA EM80) in my valve amplifier. It is used and old. I retrieved it from an old chinese radio.

I tested and it seems to be OK, but reading this I'm worry to spend time and work uselessly.

The only strange thing I noticed is that the beam (with zero grid voltage) is not straight. In the end of its lenght it get curved to the right.

About the link given before (magiceyetubes.com). I contacted Mr Howard Mariotti, the owner of the site, asking him about the EM80, and he answered me clearing my doubts. I think that is a good site about magic eyes.

Tractorfan · 20th Jan 2012, 5:42 pm

Hi,
My experience with magic eye tubes seems to be that those with the phosphor applied to the glass of the envelope (EM84, EM87) last longer than those where the phosphor is on a metal screen (EM34, EM80). It may be something to do with the cooling effect of the glass. I might be wrong, though.
In old French radios EM34s were very common, even when the rest of the set used B9A or B7G valves. I've bought a few radios that were unrestorable for a few euros and found a good magic eye therein. So it's worth having a look at tatty old radios to see what lurks inside.
Cheers, Pete

GMB · 20th Jan 2012, 6:23 pm

I would suggest that where the phosphor is coating the actual target the electrons hit it at full energy. With the EM84/87 kind the electrons have passed the final anode and as glass is not a great conductor I suggest that a lot of charge builds up and so as the electrons approach the phosphor they will be slowing right down, and this may be why it lasts much better.

I bought an EM80 when I was a child but didn't run it all that many hours. Then I fitted it as a tuning indicator to my PCR set. It has since only been run a few hundred hours I guess and already it is starting to look distinctly streaky as parts of the target don't glow so well.

I don't think I have ever encountered an EM84 or EM87 looking at all weak. They do seem the best type given a choice. Not so surprising really as they are just crude little CRTs and we all know how well they last.

paulsherwin · 20th Jan 2012, 6:41 pm

I agree that EM84s last much better than earlier types. They were standard as recording level indicators in 1960s domestic tape recorders and there are a lot of them around, both used and new.

Tractorfan · 20th Jan 2012, 6:53 pm

Hi,
I must admit, I've never seen an EM84 with "screen burn"

Cheers, Pete

kalee20 · 20th Jan 2012, 7:58 pm

The DM70 is also a magic eye that seems to last well. This has the phosphor applied to the anode, but it's a more turquoise colour than the EM34, EM80 etc - maybe it's less prone to getting 'tired'?

Tractorfan · 20th Jan 2012, 11:40 pm

Hi,
It could be due to the much lower HT current resulting in less electron bombardment plus, the "image" is a lot smaller in relation to the anode which, in this case, could be acting as a heat sink. Just a thought.
Cheers, Pete

bobbyball · 21st Jan 2012, 12:29 pm

Just to add my experiences here - I restore a lot of Continental sets and often these use the EM84 and sometimes even the EMM803 - which is like an EM84 but has an extra "box" which is used to indicate "stereo" reception with a multiplex decoder.

I have seen some truly worn out 84/803's, some so bad that there is no "indication" at all and some with very bad "screen burn". The 84 is very common still fortunately but the 803 is quite scarce now - these seem a "weaker" variety than the 84 (or 87) which seem more long lasting in comparison...

Robert

Keith · 21st Jan 2012, 4:07 pm

A last resort option for a weak EM34/EM80 type magic eye is to move the target electrode connection from the normal HT line to the reservoir capacitor (rectifier cathode). The few extra volts give a bit more brightness from the aging phosphor (albeit with a slight audio modulation of the display at high volume levels).

crackle · 29th Jan 2012, 11:49 am

Is the no signal dark area only ever 90 deg or less, it seems such a shame that it is not 180 deg. I an referring to the 6U5 types with the eye on the end of the tube, not the EM81 horizontal type.
Mike

Tractorfan · 29th Jan 2012, 12:25 pm

Hi,
I think the deflection angle is limited by the practicalities of the various electrode supports and the grid "blade" that draws the beams together and closes the gap. I don't think the voltage swing on the grid would be capable of dragging the electron stream 90° each side even if the supports allowed it. If you get my drift

.
Cheer, Pete

Leon Crampin · 29th Jan 2012, 12:54 pm

The EM71 is one of the nicest looking round eyes as the active area is a much larger proportion of the viewing area than is the case with earlier types. This is achieved by placing the cathode off centre which allows a larger display "bowl". Its short length and B8G base allow it to replace an EM34 (without the dual sensitivity feature, which is of dubious value in a radio).

I have converted a few radios which used the EM34 to an EM71 - on an adapter - at a time when these were cheaply available - regrettably prices have crept up as these devices too become scarce.

Does anyone know the difference between an EM71 and a 71A? The data is not clear.
Was there an EM72?

Leon.

Chris55000 · 27th Jul 2015, 6:54 pm

Hi!

The EM71, EM71a and EM72 were all of Lorenz manufacture with B8G (loktal) bases and separately pinned display grids (g' in British valve-base nomenclature, referred to as "gL" on the original German data!), yes there was an EM72 - this was a very unusually manufactured eye with two permanently dark sectors on its target-anode where no phosphor was applied in manufacture!

I'm curious to this day why Lorenz made an eye like this, no other British, American, Russian or Japanese valve maker has done anything like!

There's hints on assorted places of magic-eyes being made with red phosphor but I can't find evidence of this - yellow ones do exsist - some of the CM4s/EM4s were made with yellow phosphors!

Chris Williams

Mike. Watterson · 30th Jul 2015, 1:07 pm

http://www.radiomuseum.org/forum/mag..._patterns.html

The separate grid allows brightness variation.

Best to use only US & European types for replacements as they are so rare. Older types can be only 100 hours.

Use Russian and Chinese equivalents of EM80, EM81 EM85, EM87

There is a Russian type WARNING not pin compatible to replace EM34 end view types. It's not great life either, but cheap and readily available.

The side view Noval / B9A bar types are longest life.
Blue / Green phosphors seem longest life, emerald green the worst.

The Russian 1E4A-B isn't much like a DM70/DM71 but is considerably cheaper and NOS can be as late as 1981. NOS DM70 are expensive and at least 20 years older.

There are Orange and Purple "tuning indicators" but these use gas. The VFD panel is based on Magic Eye vacuum triode (no gas) and can be a wide range of colours today. Used still in some Hifi, cookers, setboxes, disc players etc.

The Tuneon was neon based.

Chris55000 · 4th Aug 2015, 7:36 am

Hi!

Just a quick note on the EM84/EM87 - altho' these have (what appears to be!) a phosphor-on-glass coating the phosphor is actually applied to a layer of transparent stannic oxide applied to the inside of the glass bulb first - if you examine one of these eyes you'll see there's a spring clip pressing against the glass - this makes the electrical connection from the phosphor/envelope coating to the target-anode plate (a thin plate with a rectangular cut-out) and thence to pin 6 of the base!

PW has a physical drawing of the EM87 in (I think!) the August 1961 issue!

Chris Williams

20th Jan 2012, 1:19 pm	#1
david3006 Tetrode Join Date: Oct 2011 Location: Holt, Norfolk, UK. Posts: 62	Magic Eyes I know little about these items, has anyone posted a beginners guide to Magic Eyes? I have several sets with dead MEs and have replaced one which now works. However to avoid changing one that may be OK but associated circuits may be duff, I would like an explanation of how they are set up so that I can make up a tester. Any offers from a genius out there please! David PS the info may be a good thing to put up on a sticky.

20th Jan 2012, 1:47 pm	#2
Pete_kaye Octode Join Date: Jun 2005 Location: Sheffield, South Yorkshire, UK. Posts: 1,227	Re: Magic Eyes There was link to someone who ran a website in U.S. just on this topic and included useful info and different moving images of different types of ME. I cannot locate it right now. Google it?

20th Jan 2012, 2:08 pm	#3
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	Re: Magic Eyes http://www.magiceyetubes.com/ ?? SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't.

20th Jan 2012, 2:42 pm	#4
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: Magic Eyes Another good site,like the test gear with four magiceyes fitted! David

20th Jan 2012, 3:13 pm	#5
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: Magic Eyes If you want to build a tester, just take a circuit from a radio. To check deflection apply some volts to the grid (pin 4 for an EM34) - a PP3 battery will be fine. The vast majority of magic eyes fail because the fluorescent phosphor wears out - if the valve has heater and HT voltage applied and is not glowing green, this is probably the explanation. You can usually see a very faint glow from a tired magic eye if you look at it in a darkened room. It's easy enough to test these valves in circuit. Just check all the voltages are there using a DMM. If the voltages are correct but the valve is dim or dead, it's gone to the big stockroom in the sky. Never buy a used magic eye unless you know and trust the seller or can see it working yourself. Anything described as 'untested' is likely to be bad.

20th Jan 2012, 5:16 pm	#6
Miguel Lopez Heptode Join Date: Dec 2011 Location: Mayabeque, Cuba Posts: 617	Re: Magic Eyes And what would be the expected lifetime for magic eyes? I pretend to put one of them (TESLA EM80) in my valve amplifier. It is used and old. I retrieved it from an old chinese radio. I tested and it seems to be OK, but reading this I'm worry to spend time and work uselessly. The only strange thing I noticed is that the beam (with zero grid voltage) is not straight. In the end of its lenght it get curved to the right. About the link given before (magiceyetubes.com). I contacted Mr Howard Mariotti, the owner of the site, asking him about the EM80, and he answered me clearing my doubts. I think that is a good site about magic eyes. __________________ When electrons move, things happen. There's nothing you can do that can't be done.

20th Jan 2012, 5:42 pm	#7
Tractorfan Dekatron Join Date: Mar 2008 Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.) Posts: 3,184	Re: Magic Eyes Hi, My experience with magic eye tubes seems to be that those with the phosphor applied to the glass of the envelope (EM84, EM87) last longer than those where the phosphor is on a metal screen (EM34, EM80). It may be something to do with the cooling effect of the glass. I might be wrong, though. In old French radios EM34s were very common, even when the rest of the set used B9A or B7G valves. I've bought a few radios that were unrestorable for a few euros and found a good magic eye therein. So it's worth having a look at tatty old radios to see what lurks inside. Cheers, Pete __________________ "Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."

20th Jan 2012, 6:23 pm	#8
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,100	Re: Magic Eyes I would suggest that where the phosphor is coating the actual target the electrons hit it at full energy. With the EM84/87 kind the electrons have passed the final anode and as glass is not a great conductor I suggest that a lot of charge builds up and so as the electrons approach the phosphor they will be slowing right down, and this may be why it lasts much better. I bought an EM80 when I was a child but didn't run it all that many hours. Then I fitted it as a tuning indicator to my PCR set. It has since only been run a few hundred hours I guess and already it is starting to look distinctly streaky as parts of the target don't glow so well. I don't think I have ever encountered an EM84 or EM87 looking at all weak. They do seem the best type given a choice. Not so surprising really as they are just crude little CRTs and we all know how well they last.

20th Jan 2012, 6:41 pm	#9
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: Magic Eyes I agree that EM84s last much better than earlier types. They were standard as recording level indicators in 1960s domestic tape recorders and there are a lot of them around, both used and new.

20th Jan 2012, 6:53 pm	#10
Tractorfan Dekatron Join Date: Mar 2008 Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.) Posts: 3,184	Re: Magic Eyes Hi, I must admit, I've never seen an EM84 with "screen burn" Cheers, Pete __________________ "Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."

20th Jan 2012, 7:58 pm	#11
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,088	Re: Magic Eyes The DM70 is also a magic eye that seems to last well. This has the phosphor applied to the anode, but it's a more turquoise colour than the EM34, EM80 etc - maybe it's less prone to getting 'tired'?

20th Jan 2012, 11:40 pm	#12
Tractorfan Dekatron Join Date: Mar 2008 Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.) Posts: 3,184	Re: Magic Eyes Hi, It could be due to the much lower HT current resulting in less electron bombardment plus, the "image" is a lot smaller in relation to the anode which, in this case, could be acting as a heat sink. Just a thought. Cheers, Pete __________________ "Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."

21st Jan 2012, 12:29 pm	#13
bobbyball Octode Join Date: Jul 2011 Location: Stockport, Greater Manchester Posts: 1,217	Re: Magic Eyes Just to add my experiences here - I restore a lot of Continental sets and often these use the EM84 and sometimes even the EMM803 - which is like an EM84 but has an extra "box" which is used to indicate "stereo" reception with a multiplex decoder. I have seen some truly worn out 84/803's, some so bad that there is no "indication" at all and some with very bad "screen burn". The 84 is very common still fortunately but the 803 is quite scarce now - these seem a "weaker" variety than the 84 (or 87) which seem more long lasting in comparison... Robert

21st Jan 2012, 4:07 pm	#14
Keith Heptode Join Date: Jan 2003 Location: Tewkesbury, Gloucestershire, UK. Posts: 693	Re: Magic Eyes A last resort option for a weak EM34/EM80 type magic eye is to move the target electrode connection from the normal HT line to the reservoir capacitor (rectifier cathode). The few extra volts give a bit more brightness from the aging phosphor (albeit with a slight audio modulation of the display at high volume levels). __________________ Keith Yates - G3XGW VMARS & BVWS member http://www.tibblestone.com/oldradios/Old_Radios.htm

29th Jan 2012, 11:49 am	#15
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: Magic Eyes Is the no signal dark area only ever 90 deg or less, it seems such a shame that it is not 180 deg. I an referring to the 6U5 types with the eye on the end of the tube, not the EM81 horizontal type. Mike

29th Jan 2012, 12:25 pm	#16
Tractorfan Dekatron Join Date: Mar 2008 Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.) Posts: 3,184	Re: Magic Eyes Hi, I think the deflection angle is limited by the practicalities of the various electrode supports and the grid "blade" that draws the beams together and closes the gap. I don't think the voltage swing on the grid would be capable of dragging the electron stream 90° each side even if the supports allowed it. If you get my drift. Cheer, Pete __________________ "Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."

29th Jan 2012, 12:54 pm	#17
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Magic Eyes The EM71 is one of the nicest looking round eyes as the active area is a much larger proportion of the viewing area than is the case with earlier types. This is achieved by placing the cathode off centre which allows a larger display "bowl". Its short length and B8G base allow it to replace an EM34 (without the dual sensitivity feature, which is of dubious value in a radio). I have converted a few radios which used the EM34 to an EM71 - on an adapter - at a time when these were cheaply available - regrettably prices have crept up as these devices too become scarce. Does anyone know the difference between an EM71 and a 71A? The data is not clear. Was there an EM72? Leon.

27th Jul 2015, 6:54 pm	#18
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,874	Re: Magic Eyes Hi! The EM71, EM71a and EM72 were all of Lorenz manufacture with B8G (loktal) bases and separately pinned display grids (g' in British valve-base nomenclature, referred to as "gL" on the original German data!), yes there was an EM72 - this was a very unusually manufactured eye with two permanently dark sectors on its target-anode where no phosphor was applied in manufacture! I'm curious to this day why Lorenz made an eye like this, no other British, American, Russian or Japanese valve maker has done anything like! There's hints on assorted places of magic-eyes being made with red phosphor but I can't find evidence of this - yellow ones do exsist - some of the CM4s/EM4s were made with yellow phosphors! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! Last edited by Chris55000; 27th Jul 2015 at 6:58 pm. Reason: Typos!

30th Jul 2015, 1:07 pm	#19
Mike. Watterson Heptode Join Date: Dec 2014 Location: Limerick, Ireland. Posts: 901	Re: Magic Eyes http://www.radiomuseum.org/forum/mag..._patterns.html The separate grid allows brightness variation. Best to use only US & European types for replacements as they are so rare. Older types can be only 100 hours. Use Russian and Chinese equivalents of EM80, EM81 EM85, EM87 There is a Russian type WARNING not pin compatible to replace EM34 end view types. It's not great life either, but cheap and readily available. The side view Noval / B9A bar types are longest life. Blue / Green phosphors seem longest life, emerald green the worst. The Russian 1E4A-B isn't much like a DM70/DM71 but is considerably cheaper and NOS can be as late as 1981. NOS DM70 are expensive and at least 20 years older. There are Orange and Purple "tuning indicators" but these use gas. The VFD panel is based on Magic Eye vacuum triode (no gas) and can be a wide range of colours today. Used still in some Hifi, cookers, setboxes, disc players etc. The Tuneon was neon based. Last edited by Mike. Watterson; 30th Jul 2015 at 1:18 pm.

4th Aug 2015, 7:36 am	#20
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,874	Re: Magic Eyes Hi! Just a quick note on the EM84/EM87 - altho' these have (what appears to be!) a phosphor-on-glass coating the phosphor is actually applied to a layer of transparent stannic oxide applied to the inside of the glass bulb first - if you examine one of these eyes you'll see there's a spring clip pressing against the glass - this makes the electrical connection from the phosphor/envelope coating to the target-anode plate (a thin plate with a rectangular cut-out) and thence to pin 6 of the base! PW has a physical drawing of the EM87 in (I think!) the August 1961 issue! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!