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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 12th May 2024, 2:43 pm   #1
mediaseller
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Default Dim Bulb Tester Alternative

Hi.

I made a dim bulb tester a few years ago and loaned it out. It came back without the bulb a while ago, so I have managed to order some incandescent bulbs from eBay.

I'm good at loosing stuff, so going forward to when we can't get the correct bulbs in the future, is there an alternative to the dim bulb tester?

Thanks in advance.
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Old 12th May 2024, 2:49 pm   #2
Radio Wrangler
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Default Re: Dim Bulb Tester Alternative

There isn't a ban on low voltage filament bulbs for vehicle applications, so twenty 5 W 12V bulbs in series could be used. Of course, this would pose a bit of a support and storage issue. Dare I suggest a small fir tree in a pot?

David
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Old 12th May 2024, 4:02 pm   #3
The Philpott
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Default Re: Dim Bulb Tester Alternative

'Terry Clip' a few of the spares you've just bought to a joist in the loft or workshop so they can't get lost; then buy a few more.

Dave
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Old 12th May 2024, 4:56 pm   #4
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Default Re: Dim Bulb Tester Alternative

Just having a thought

Could one not use a few of the 450 Volt motor start capacitors and an AC current meter with say a couple of 25uF ones first in series to give 12.5 uF. Reactive impeadance you would have 255 Ohms in series, with just one in series you would have 127 Ohms and then with the two in parallel you would have 63 Ohms in series, all assuming a resistive load of course. But if it is used to replace resistive droppers why not to power the radio under test?

Less light and heat to deal with.

Or am I missing something in my train of thought?

Adrian
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Old 12th May 2024, 5:05 pm   #5
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Default Re: Dim Bulb Tester Alternative

What would be missing is that tungsten filaments are not constany impedance, they are positive temperature coefficient thermistors.

If the set starts taking too much current, then the bulb(s) heats up and its effective resistance climbs rapidly, reducing the available current to the set. It gives a foldback chatacteristic.

David
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Old 12th May 2024, 5:09 pm   #6
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Default Re: Dim Bulb Tester Alternative

There are no plans to withdraw 15W and 25W incandescent oven bulbs that I know of. The operating temp is too high for LEDs. You could build a limiter with 4-6 of these in parallel, though it would cost more than buying a 100W GLS lamp from Tesco a decade ago.

The bulb in a lamp limiter should have an extremely long life given the pattern of use.

No doubt incandescent lamps will continue to be available from dodgy Chinese suppliers indefinitely - if they're happy to supply extremely dangerous drugs and chemicals with no questions asked, a few naughty light bulbs shouldn't be a problem.
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Old 12th May 2024, 5:20 pm   #7
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Default Re: Dim Bulb Tester Alternative

I have used old H4 car headlamp bulbs in the past as current limiters in 12 and 24 Volt applications. A visit to your local car workshop will get you plenty of these, they have two filaments, one for normal and one for dip beam.

They get replaced when the normal filament burns out, but the dip beam filament - intended to do around 4.5A at 12V - is still OK.

They are great as a safety limiter when working on transistor circuits.
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Old 12th May 2024, 5:20 pm   #8
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Default Re: Dim Bulb Tester Alternative

Can't imagine there is much demand for NOS lamps for lighting use, last time I needed some I had no problems finding them at car boots, markets and online selling sites.

David
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Old 12th May 2024, 5:23 pm   #9
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Default Re: Dim Bulb Tester Alternative

Most forum members will have a box of old incandescents if anybody is desperate for one.
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Old 12th May 2024, 5:36 pm   #10
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Default Re: Dim Bulb Tester Alternative

Quote:
Originally Posted by paulsherwin View Post
Most forum members will have a box of old incandescents if anybody is desperate for one.
Yes, but rather like valves I am finding the values I want are not in that box.

Oh, sudden thought: perhaps a few U or P series valve heaters as substitute might be a use for old worn TV pulls?
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Old 12th May 2024, 5:39 pm   #11
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Default Re: Dim Bulb Tester Alternative

The trouble with that is the power being dumped isn't visible as it is with a lamp filament.
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Old 12th May 2024, 7:11 pm   #12
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Default Re: Dim Bulb Tester Alternative

Search online for "Rough Service" lamps. These are still available.
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Old 12th May 2024, 9:42 pm   #13
Joe_Lorenz
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Default Re: Dim Bulb Tester Alternative

Dear Paul:
Quote:
Originally Posted by paulsherwin View Post
The trouble with that is the power being dumped isn't visible as it is with a lamp filament.
Oh I know that would be a somewhat funny idea - but you have just generated the inspiration to employ a RS 1026, QQE03/60 or TB3/750 as a current limiter lamp! Those make the heater current visible!

Joe
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Old 12th May 2024, 10:17 pm   #14
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Default Re: Dim Bulb Tester Alternative

If indeed Rough Service lamps are still available, these are preferable to the standard item for this particular purpose....one has to be on the lookout for cheapies or counterfeit badging without ballotini fuses though, as i've had a couple blow up.

Dave
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Old 12th May 2024, 10:33 pm   #15
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Default Re: Dim Bulb Tester Alternative

A quick look now on Ebay found quite a few 100W GLS tungsten filament lamps with BC caps available in packs of 5 and 10's and quite a few are NOS so should be of a high quality.

Christopher Capener
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Old 13th May 2024, 7:58 am   #16
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Default Re: Dim Bulb Tester Alternative

Are there not still heat-lamp bulbs available?
The advantage of lamps meant to warm things is that they absolutely can't be made "low power".
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Old 13th May 2024, 9:07 am   #17
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Default Re: Dim Bulb Tester Alternative

I agree incandescent bulb limiters are a workshop essential, both for mains and LV circuits; I made a M10 bulb limiter this year and use it all over the place. There are still several of these 60W globe bulbs left, local members would be welcome to call in for a couple. T
Having a pair means you can limit at ¼ or ½ Amps
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Old 13th May 2024, 10:00 am   #18
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Default Re: Dim Bulb Tester Alternative

One post moved to a new thread here:-

https://www.vintage-radio.net/forum/...d.php?t=210945
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Old 13th May 2024, 10:17 am   #19
Craig Sawyers
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Default Re: Dim Bulb Tester Alternative

https://www.thelightbulb.co.uk/lightbulbs/incandescent/

And

https://www.lampco.co.uk/collections/incandescent-gls

I've used both in the past

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Old 13th May 2024, 1:13 pm   #20
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Default Re: Dim Bulb Tester Alternative

Quote:
Originally Posted by GMB View Post
Are there not still heat-lamp bulbs available?
The advantage of lamps meant to warm things is that they absolutely can't be made "low power".
Those are sold in equine/farming stores and are often rated at 100 to 250W.
They are normally reflector style.
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