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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 24th May 2020, 11:22 am   #1
stevehertz
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Default Unmarked T style bulbs - rating?

I've got a packet of T style bulbs that I obviously bought for a project, used one or two then packed it away. Trouble is, no markings on bag or bulbs.

To ascertain their rating I plan to connect a DC supply and monitor current and voltage (voltage at the bulb terminals) and look for a 'reasonable' level of illumination and take the bulb rating as that being shown for V and I? I suppose I could document a small range over which the bulb seems usable. Obviously an over-bright bulb would have a limited lifespan.

Anyone think of a better way?
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Old 24th May 2020, 11:39 am   #2
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Default Re: Unmarked T style bulbs - rating?

I don't recognise the term 'T style' myself, but those look like standard G4 12V halogens. If so, the commonest ratings are 10W and 20W. Other wattages are available. Try running one at 12V for a few seconds - it should be pretty bright and hot. As usual, don't tough the glass with fingers.
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Old 24th May 2020, 11:41 am   #3
Lucien Nunes
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Default Re: Unmarked T style bulbs - rating?

Capsule T/H lamps were made for a limited number of voltages; I don't think I've had any in that power range that were not either 12 or 24V. Even a small overvoltage (e.g. 5%) will dramatically shorten the life, however a modest undervoltage will easily be seen as low illumination and colour temperature, therefore it will be easy to home-in on the correct voltage and the current will reveal the wattage, which is likely to be a round number.
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Old 24th May 2020, 11:53 am   #4
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Default Re: Unmarked T style bulbs - rating?

My first camcorder's movie light took a 6V bulb of that type, but it certainly wasn't a commonly-available item.
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Old 24th May 2020, 11:54 am   #5
stevehertz
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Default Re: Unmarked T style bulbs - rating?

Humber you're right, I'm mixing them up with Wedge 'T' style bulbs that I've also used in the recent past. On examination, the packet says, 'CA-165-20W'. So I'll apply a voltage and increase it to 12V and see if that seems about right as looking at what's available, 12V seems to be the most common.
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Old 24th May 2020, 1:38 pm   #6
paulsherwin
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Default Re: Unmarked T style bulbs - rating?

I agree with others that 12V is by far the likeliest voltage rating. They will be pretty bright at full voltage, not like a traditional panel lamp at all.

You can sacrifice one in destructive testing - take it to 12V and it should give a bright slightly warm light, take it to 24V and it should pop. Wear a visor!
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Old 24th May 2020, 1:50 pm   #7
stevehertz
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Default Re: Unmarked T style bulbs - rating?

Quote:
Originally Posted by Humber888 View Post
I don't recognise the term 'T style' myself, but those look like standard G4 12V halogens. If so, the commonest ratings are 10W and 20W. Other wattages are available. Try running one at 12V for a few seconds - it should be pretty bright and hot. As usual, don't tough the glass with fingers.
FYI, The griff on T bulbs here: https://en.wikipedia.org/wiki/Wedge_base
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Old 24th May 2020, 1:51 pm   #8
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Default Re: Unmarked T style bulbs - rating?

Thanks everyone for your input.
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Old 24th May 2020, 5:06 pm   #9
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Default Re: Unmarked T style bulbs - rating?

Simpler explanation:

What is T type light bulb?
The T type miniature light bulbs category is large and includes many applications: indicator, auto, emergency, aircraft, instrument and signal. The number after the 'T' is the diameter of the glass in 1/8 inch increments. A T4 bulb, for example, has a diameter of 4/8 or 1/2 inch.
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Old 24th May 2020, 10:51 pm   #10
Graham G3ZVT
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Default Re: Unmarked T style bulbs - rating?

This lamp has a big 6v toroidal transformer I only had a 12v bulb so it's very dim

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I use it as a night light.

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Old 25th May 2020, 8:39 pm   #11
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Default Re: Unmarked T style bulbs - rating?

One of my motorcycles has a device known as a maglita. It gives an HT spark (after a fashion) and provides a 6v LT output (after a fashion). It is so underpowered that the main headlight bulb is 6V 12W, a size quite unobtainable today. i found these capsule lamps could be sourced in 6V, and I bought some in 10W and 18W ratings. Since my bike did not have a sidecar, for which 3W could be allocated for the combined front and rear lamp, and since I had dispensed with the 3W rear light in favour of a home assembled LED device, I decided it could handle an 18W bulb, so I mounted both an 18W and 10W on a small piece of coppered PCB and fixed to a suitable base. I now have a tolerable main/dip beam. Les.
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