Teardown: Osram St151 4-22W Series Glow Starter

If you thought I had said everything I needed to say about starters back in my glow lamp article, you were wrong! When visiting a local hardware store, I came across a different type of starter, known as a series type starter.

In my first posting, all of the starters I was looking at were known as universal starters. These are often denoted as 4 to 65W starters, designed for use with just a single lamp. The other type of starter is known as a series starter, denoted for use with 4 to 22W lamps in series.

So, I decided to buy some just for fun and write about them.

The Product

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Osram is a reputable lighting company, and their St 111 universal starters are pretty ubiquitous with a white shell. The St 151 is their series starter and comes in a pale green shell, sold in pairs for a few dollars.

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The starters are made in Italy, and are designed for use in series lamp configurations schematically shown on the rear. This type of configuration is normally only seen in 230v countries, as there would not otherwise be enough voltage to light both lamps in series.

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The plastic of the can is opaque, which is unfortunate if you wanted to use it “as is” for your DIY glow lamp, but it does have a very nice shape including moulded text at the end of the cap.

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The starter is built upon a bakelite insulator base, and features a solid contact with a single hooked bimetallic strip. A parallel RF suppression capacitor is also fitted.

Why Series Starters?

Series starters are a necessity in the case of the series lamp configuration, as the starter has to be able to start its glow discharge with two starters essentially in series. Universal starters only start their discharge at about 170-190v, which means that two of them require over 340v. This doesn’t happen on most 230-240v lines, and only at the peak of the AC waveforms at the best, and thus the starter doesn’t operate correctly as the discharge isn’t strong enough to heat up the bimetallic strip and set off the inductive kick (or isn’t there).

As a result, the series starters must have a lower voltage breakdown. On testing it, it showed about 90v breakdown, almost precisely half that of the universal starters.

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This was exactly as expected, from the rationale of having a different type of starter. It also does mean that it cannot run lamps as long as the universal, as the lamp’s running voltage must be quite a bit less than the starter’s breakdown voltage, so as to preferentially draw current so the starter doesn’t then begin the starting process again. As the running voltage is proportionally related to the tube length, that’s why the series starters are used for up to 22w tubes.

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When run from DC, only one electrode glows at a time. The starting tube glows a nice orange red, unlike a salvaged St 111 (not posted about) which glowed a dim blue. I suppose if you want to build your own glow lamp, especially from USB where the inverted voltage is limited, then series starters will give you twice as many bulbs in series for the same voltage. You will need to use a clear enclosure or something to keep fingers away from the high voltage – for example, you could transplant the starter base into the Philips S10-P shells.

Conclusion

Series starters are used where tubes are run in series, and have half the voltage drop of the universal starters, so that they will fire when line voltage is applied. Their reduced voltage drop of ~90v is much closer to traditional neon bulbs, and means more bulbs in series from a single CCFL inverter – so probably well worth looking at.

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One Response to Teardown: Osram St151 4-22W Series Glow Starter

  1. blouis79 says:

    You might be interested in electronic fluoro starters. More efficient, faster, less lamp wear. The only odd thing is that none of the major lamp manufacturers seem to make them.

    http://users.tpg.com.au/pschamb/light.html

    I got some from UK by mail – cheap postage. Work great. Should hopefully last since they don’t have electrolytic caps.
    http://www.tabelek.co.uk/product-electronic-fluorescent-tube-starters.asp

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