Help Identify Tiny Lamp

[vidarr]

I need to replace this tiny light that goes inside a coffee/espresso machine. I tried a couple local stores and they don't know, or have, anything. It is a 120v appliance. There is also a resistor before the bulb, but it looks like someone did a repair near the light and had to MacGyver it back together with a candle and some clay. The resistor is covered and I could not clean it off without removing the bands. I need help to identify the bulb and resistor so I can replace it. Thanks.

[Armadillo]

https://www.ebay.com/itm/20pcs-Neon-Bulb-Indicator-5mm-Lampada-Lamp-Red-Neon-Light-5-mm-Neon-Light/222950531484?hash=item33e8e3219c:g:kywAAOSw43Ba4tyr:rk:7:pf:0

[ciccio]

It is a standard Neon bulb, they are everywhere.  https://en.wikipedia.org/wiki/Neon_lamp
If you cannot find  locally, they are inside any illuminated AC switch, so you can cannibalize one.
The series resistor is in the order of 100 K (for 230 V ac).
This is an axample:https://uk.rs-online.com/web/p/neon-indicator-lamps/0105017/
Best regards

[vidarr]

Thanks guys. They don't sell these here. I will have to pull one from a switch -- thanks for that tip.

[Ian.M]

Unless the glass has cracked/broken that neon bulb is probably OK.  Remove the solder blob, replace the resistor and try it . . . 

[vidarr]

How do I calculate the resistance for 120V mains power? I don't know the current. I don't have a datasheet for the lamp. There should be a "standard" size resistor most people use right?

[Armadillo]

The current is about 1.5mA and the minimum voltage across is 60V; hence the resistor should be;

= (120 - 60) / 1.5mA = 40Kohm;

Size of resistor = 90mW; Select 1/4W is OK.

How do I calculate the resistance for 120V mains power? I don't know the current. I don't have a datasheet for the lamp. There should be a "standard" size resistor most people use right?

[Armadillo]

If you want it slightly brighter then select 36Kohm @1/4W.

[soldar]

You can start with 100K and adjust down according to brightness wanted.  Ambient light makes quite a difference.

[Nusa]

First off, have you tried measuring the old resistor with your meter? If you get a reasonable reading, that may not have been the failure point.

At 120V, I'd pick 33Kohm for an NE-2H lamp, or 120Kohm for NE-2. They look the same, of course.
You don't know what you have, so I'd try 120K first. If it works, do NOT try 33K.
Pick a higher value if you think it's too bright...you presumably remember what it looked like before.

Your other option is to replace it with an LED indicator circuit. You'll lose the neon flicker, but otherwise quite adequate.

[vidarr]

I had an 89k resistor handy and it worked well. Thanks guys.

The little light looks so much better without the red plastic cover. It looks kind of cool. I have to put the cover back on though.