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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 28th Jan 2010, 10:12 pm   #1
Phil G4SPZ
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Default Magic eye valve types

I'm building a simple test rig for magic eye valves, as these can't easily be tested on typical valve testers. The common types that I've come across in British vintage radios include Y63, Y65 (classic octal shape, end-on view), EM34 (slim octal, end-on view), EM80, EM81 (B9A upright side-view) and EM84 and EM85 (B9A horizontal bar type). A number of equivalents were made, but they all boil down to the foregoing basic types.

Does anyone know of any other types used?
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Old 28th Jan 2010, 10:23 pm   #2
Leon Crampin
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Default Re: Magic eye valve types

EM71 (Loctal)
AC/ME (B7)
ME41/91 (MO)
1629 (IO)
Various side contact versions of the octal types and AC/DC derivatives.

Why build a rig?

An AVO 2 panel tester will test the whole lot. Configure the tester to test the triode as normal (you can then measure its gm and check its h-k resistance), then connect the screen grid supply of the tester to the target so the eye lights up. You can vary the "screen" voltage to check the brightness and the sensitivity of the eye at various target voltages.

Finally, operating the "C Ins" switch on the tester will open the eye.

Leon.
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Old 28th Jan 2010, 10:27 pm   #3
Phil G4SPZ
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Default Re: Magic eye valve types

Quote:
Originally Posted by Leon Crampin View Post
Why build a rig? An AVO 2 panel tester will test the whole lot...
Because I haven't got an AVO 2-panel tester! Just a Weston TV-4A/U, which won't test eyes, but thanks for the useful information and type numbers Leon.
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Old 28th Jan 2010, 10:35 pm   #4
Leon Crampin
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Default Re: Magic eye valve types

Hmm. I had a TV-7/U tester once and I still have the valve charts. All the American eyes are in there - eg:

6U5 6.3 GR5-4030 0 100 A 3 (eye open).

I think with a little creative thought, most testers can be configured to test an eye but I'm not familiar with the TV-4A/U.

Leon.

Last edited by Leon Crampin; 28th Jan 2010 at 10:41 pm.
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Old 28th Jan 2010, 10:44 pm   #5
Michael Maurice
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Default Re: Magic eye valve types

There is a UM84 and possibly UM87, also EMM80 as found in Revox F36 tape recorders. and EAM85 found in early Tandbergs and Kortings.

I've not heard of EM85 but there was EM87

Last edited by Michael Maurice; 28th Jan 2010 at 10:44 pm. Reason: addition of words
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Old 29th Jan 2010, 9:43 am   #6
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Default Re: Magic eye valve types

Don't forget the DM70. It has a 1.4 volt filament and was used in battery radios and some tape recorders. Display is upright side view.

DFWB.
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Old 29th Jan 2010, 9:57 am   #7
Ian B
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Default Re: Magic eye valve types

There's also the TV4 which has a side-contact base.

Ian Blackbourn
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Old 29th Jan 2010, 10:01 am   #8
Tim
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Default Re: Magic eye valve types

AC/ME,UM4,UM80

A good place to look is here

http://www.r-type.org/inx/inx00408.htm

I have an EM1 somewhere, and a 12XXX(can't remember exact nomenclature) with a 12 volt filament(sadly O/C new in box ) and octal base.
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Last edited by Tim; 29th Jan 2010 at 10:07 am.
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Old 29th Jan 2010, 10:17 am   #9
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Default Re: Magic eye valve types

A few useful Magic Eye sites:-

http://www.akh.se/tubes/eyes.htm

http://www.magiceyetubes.com/

http://www.solorb.com/elect/misc/magiceye/

Regards, Mick.
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Old 29th Jan 2010, 10:44 am   #10
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Default Re: Magic eye valve types

Although very uncommon there is also the Mullard TV4. It was used in a few Ekco sets including the AC97. If you find a duff one & wish to replace it you'll find they are as rare as hen's teeth and cost a small fortune.

Although you have a Weston tester I believe that some of the AVOs have two terminals and a shorting link which can be removed and replaced by a resistor which will then be in series with the triode anode and the tube can be checked under normal working conditions by varying Vg.

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Old 29th Jan 2010, 11:01 am   #11
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Default Re: Magic eye valve types

Quote:
Although very uncommon there is also the Mullard TV4. It was used in a few Ekco sets including the AC97. If you find a duff one & wish to replace it you'll find they are as rare as hen's teeth and cost a small fortune.
Oh good, I got one for a pound when Hanneys of Bath was closing down! I haven't tested it though, so I wont retire yet!
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Old 29th Jan 2010, 11:12 am   #12
Barry Lloyd
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Default Re: Magic eye valve types

Im my junk box I have an EM11. I don't remember what set it came out of (it must be at least 30 years ago!). I doubt that it's very common, though.

Barry
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Old 29th Jan 2010, 11:31 am   #13
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Default Re: Magic eye valve types

hi,one point to watch out for is that the base for em80 and em87 are different,pin3 is ht on em80 while its ground on em87.
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Old 29th Jan 2010, 11:47 am   #14
Leon Crampin
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Default Re: Magic eye valve types

If you're testing an eye on a valve tester there's no need for an anode resistor. As long as you separate out the two supplies for the anode and target (I use the screen supply for this), you can make the eye "work" just by adjusting the triode anode voltage on the tester. As the deflection electrode is directly connected to the triode anode, this is a perfectly valid check and replicates what happens in use.

You can test the triode as you would any other triode, first. Magic eye triodes usually have fairly low gms of about 1 mA/V. This figure is never given in the data, but I've tested so many this way I know what to expect.

Sadly, it's always target degradation which kills an eye - I've never seen a faulty or even low emission triode. I haven't thought of a fix for this yet...

Leon.
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Old 29th Jan 2010, 12:26 pm   #15
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Default Re: Magic eye valve types

Also there's 6X6 (UX6 base), I have one NOS.

And there's an EFM1, combining a magic eye and an AF pentode, which Philips (who else?) used in at least one of their sets.

The TV4, aforementioned, is equivalent to the A39A, and I need one for my Ever Ready 5033 radio - if I'm not going to modify it...
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Old 29th Jan 2010, 8:09 pm   #16
Phil G4SPZ
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Default Re: Magic eye valve types

Quote:
Originally Posted by Leon Crampin View Post
I had a TV-7/U tester once... I think with a little creative thought, most testers can be configured to test an eye but I'm not familiar with the TV-4A/U.
The TV-4A/U is a simple 'tube checker' rather than a valve tester, and measures total emission only, by applying around 30 volts AC to the electrodes and measuring total cathode current via a meter with a calibrated shunt.

Thanks to everyone for their suggestions. The www.magiceyetubes.com website suggested by Mick is a real mine of information and gives me practically everything I need to know. Interesting facts are that the design life of a magic eye is around 1,000 hours, and short of boosting the target potential it seems there is little that can be done to rejuvenate expired eyes.

Great stuff, thanks again,
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Old 30th Jan 2010, 8:26 am   #17
Neil Purling
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Default Re: Magic eye valve types

Speaking of magic eye tubes: Is the Russian (6E1P) EM80 clone a plug in replacement for a Mullard original? I wondered if there were any connections that were different.
I have the base connections for a genuine Mullard EM80, not a Russian 6E1P.
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Old 30th Jan 2010, 1:43 pm   #18
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Default Re: Magic eye valve types

I'm sure I read somewhere of a red (ish) magic eye, possibly in the EM8xxx series, anyone else heard of it?
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Old 30th Jan 2010, 5:51 pm   #19
Phil G4SPZ
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Default Re: Magic eye valve types

Quote:
Originally Posted by Neil Purling View Post
Is the Russian (6E1P) EM80 clone a plug in replacement for a Mullard original? I wondered if there were any connections that were different. I have the base connections for a genuine Mullard EM80, not a Russian 6E1P.
This site http://www.russiantubes.com/prop.php?t=12&p=110 gives the pin-out of the 6E1P. It's quoted as a plug-in equivalent.
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