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Old 18th Nov 2023, 11:32 am   #1
Tinker1966
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Default Christmas Milk glass bulb repair ??

Hello all - I wonder if any of you knowledgable people can help me out ??

I have some old milk glass bulbs that no longer work.

It occures to me that if the metal screw connector were removed and the glass filed away that it might leave enough room to insert a small LED or similar and then reapply the screw fitting allowing the bulb to be put back into the string of 12.

However my ideas are running ahead of my knowledge !

I have no idea if an LED of approx 20v is available that would run on AC ... or where to look for such a thing.

Can anyone help or tell me I'm mad and that it's a ridiculous idea !!

Many thanks
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Old 18th Nov 2023, 11:51 am   #2
60 oldjohn
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Default Re: Christmas Milk glass bulb repair ??

You may get some ideas from "Big Clive" on YouTube.

John.

https://www.youtube.com/results?sear...istmas+lights+

This is one that may interest you, https://www.youtube.com/watch?v=ewO-r8_d3uw
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Last edited by 60 oldjohn; 18th Nov 2023 at 12:03 pm. Reason: Added last line.
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Old 18th Nov 2023, 11:58 am   #3
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Default Re: Christmas Milk glass bulb repair ??

It's possible to do this, but it's not easy or straightforward. Firstly you need to dismantle the bulb and modify the extremely fragile glass envelope without breaking it. You then need to add series and parallel resistors and LEDs to make the fitting emulate a 20V incandescent MES bulb.

I would leave this unless you are very determined and have the right skillset and tools.
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Old 18th Nov 2023, 12:43 pm   #4
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Default Re: Christmas Milk glass bulb repair ??

I think it's certainly possible to do and it would be lovely to bring the set of lights int the 21st century.

Paul is right though, it would entail a fair bit of thought. The first thing to do is establish the resistance of a single bulb when it is lit - this is much larger than the resistance when the bulb is cold. To work this out measure the current flowing through a single (good) bulb when it is powered from 20V (240/12) either AC or DC. When you've done this we'll get a little circuit sorted out for you.


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Old 18th Nov 2023, 1:01 pm   #5
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Default Re: Christmas Milk glass bulb repair ??

I would only consider doing this if the bulb was a 'figural' bulb (Santa, snowmen etc) as these are like gold dust (like these). Ordinary 20V MES olive bulbs are still available both new and secondhand, and while not cheap at about £4 a pop the work involved in 'converting' a blown one is prohibitive.

These bulbs are normally rated at 3W 150mA.
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Old 18th Nov 2023, 2:45 pm   #6
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Default Re: Christmas Milk glass bulb repair ??

Remember that the light from a LED comes out the end and in quite a narrow angled beam, so just a single one inside the glass envelope would look extremely odd.

Putting several LEDs into the envelope so you had one pointing at the end and others pointing at the circumference to provide both axial and radial illumination could prove tricky.
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Old 18th Nov 2023, 2:51 pm   #7
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Default Re: Christmas Milk glass bulb repair ??

I think you'd have problems dissipating the heat required in anything that can be shoved up the end of a figural bulb. I assume you intend to run it in a string of otherwise intact bulbs, so you dont want to either over-run the new one or risk over-running all the others.
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Old 18th Nov 2023, 3:21 pm   #8
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Default Re: Christmas Milk glass bulb repair ??

A lot depends on the dimensions of your Milk Glass Bulb.

It is possible to buy COB LEDS in the form of long narrow strips.
These are pure LEDS and you would need to connect them to a current regulated power supply outside the bulb.

They only emit light from one side. You may have to fit them back-to-back to provide 360 degree lighting.
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Old 18th Nov 2023, 3:21 pm   #9
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Default Re: Christmas Milk glass bulb repair ??

Well yes, as per Kevin's comment.

Also, I've an idea that the cement holding the screw base to the glass will be five times stronger than the glass itself, and also impervious to heat or chemical attack. Then if you're lucky you expose the base of the glass envelope that is pinched down to a narrow end..

Probably about time the 'Xmas fairy lights' (?) thread was reopened, but it's unlikely that will help you with this particular idea!

Dave
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Old 18th Nov 2023, 4:02 pm   #10
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Default Re: Christmas Milk glass bulb repair ??

I have used Araldite to repair working bulbs where the glass is loose in its brass socket.

A couple of decades ago I added four extra bulbs to my vintage set of lights from a broken set so that the bulbs are running at 15V instead of 20V. It doesn't significantly reduce their brightness but does significantly extend their life.
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Old 18th Nov 2023, 4:02 pm   #11
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Default Re: Christmas Milk glass bulb repair ??

You might find it possible to insert a small filament lamp into the old envelope, which could be easier to match to the original string.
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Old 18th Nov 2023, 4:13 pm   #12
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Default Re: Christmas Milk glass bulb repair ??

Quote:
Originally Posted by The Philpott View Post
Probably about time the 'Xmas fairy lights' (?) thread was reopened

Dave
Done:-

https://www.vintage-radio.net/forum/...ad.php?t=54943
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Old 18th Nov 2023, 4:52 pm   #13
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Default Re: Christmas Milk glass bulb repair ??

The problem will be that there'll be nowhere for the heat to dissipate inside the globe of the old bulb - that's if you can cut it off without busting it.

I always run old Christmas lights on a reduced voltage via a Variac - no blown bulbs for years!
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Old 18th Nov 2023, 5:49 pm   #14
Tinker1966
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Default Re: Christmas Milk glass bulb repair ??

Crikey ! What a great response.

I was thinking about figural milk glass bulbs as I thought they are becoming rarer and as such more expensive.

I attach a couple of pics of one I managed to remove the screw cap from and grind the glass down thinking it might be possible to pop a small diameter Led through it.

Having read everyone’s replies I’m realising this isn’t as simple as I had naively hoped - ah well, you live and learn.

I was interested to read that the cement holding the caps is so hard - what was used ? Do we know ? The one I did came off easily but that must have been luck I think.

Thanks again for all the info - much appreciated
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Old 18th Nov 2023, 5:52 pm   #15
Tinker1966
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Default Re: Christmas Milk glass bulb repair ??

Quote:
Originally Posted by Brigham View Post
You might find it possible to insert a small filament lamp into the old envelope, which could be easier to match to the original string.
This seems likely the best option - I shall look into it
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Old 19th Nov 2023, 6:51 pm   #16
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Default Re: Christmas Milk glass bulb repair ??

Quote:
Originally Posted by Techman View Post
I always run old Christmas lights on a reduced voltage via a Variac - no blown bulbs for years!
I always put a series diode inside the mains plug.
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