Author Topic: Reviving a 50w MV lamp with an 80w ballast  (Read 431 times)
108CAM
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Reviving a 50w MV lamp with an 80w ballast « on: May 09, 2022, 10:39:28 PM » Author: 108CAM
I have a 50w MV lamp with very low hours however it won't start on any of my 50w ballasts. I think the mercury has condensed and bridged the starting electrode with the main electrode meaning the lamp won't strike. I was thinking of putting it inside an 80w fixture to see if the higher starting current will cause the lamp to strike. I would then let the lamp warm up a tiny bit so the mercury starts to vaporise then unplug the fixture and try it on 50w ballast.
I'm just checking to see if it's safe to do or weather it will even work in the first place
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Medved
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Re: Reviving a 50w MV lamp with an 80w ballast « Reply #1 on: May 10, 2022, 07:24:36 AM » Author: Medved
No, do not do that.
Using 80W ballast won't revive it. With the starting probe shorted, the mains is not enough to strike the discharge. When not started, there is no current, so the lamp[ sees the full mains voltage regardless of what ballast you will use (speaking about series choke ballasts here). It may start after some time once there would be some voltage spike in the mains, again regardless what ballast would be connected that time. If it happens with the 80W choke, the electrodes would be overloaded and may get destroyed (the 50W have very small overload margin).

What you may try instead is to temporarily short (just brief short) the lamp by a piece of jumper wire and so create an inductive kick voltage by that. Chances are, this extra voltage spike will eventually ignite the discharge and once ignited, the mercury will evaporate off. Then it is important to always operate the lamp with the starting probe on the upper side, so the condensed mercury won't pool there again.
Just be careful, you are dealing with mains voltage. So maybe better idea would be to wire some light switch parallel to the lamp and clicking with it a few times, so you won't be dealing with open conductors with voltages on them.
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Re: Reviving a 50w MV lamp with an 80w ballast « Reply #2 on: May 10, 2022, 06:45:30 PM » Author: 108CAM
Thanks. I'm glad I asked here first. There is a chance that one of the electrodes may have been fried during a ballast burnout as the ballast it was originally running on is shot
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Michael
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Re: Reviving a 50w MV lamp with an 80w ballast « Reply #3 on: May 12, 2022, 12:20:38 AM » Author: Michael
Or try to use a superimposed ignitor for HPS 50/70W lamps with the appropriate ballast. The 1.3kV may help to create an initial arc. But if you do this don’t hot re-strike the lamp with ignitor as then it can destroy the resistors of the starting probe or even form an arc in the outer bulb (as happened already on one dead Philips lamp with a 4kV ignitor)

I did revive may old dead lamps in that way with success. 
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Re: Reviving a 50w MV lamp with an 80w ballast « Reply #4 on: May 12, 2022, 12:23:03 AM » Author: 108CAM
Does superimposed mean the HPS ignitor is connected to the MV ballast as if it was a HPS ballast?
« Last Edit: May 12, 2022, 12:37:08 AM by 108CAM » Logged

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Re: Reviving a 50w MV lamp with an 80w ballast « Reply #5 on: August 04, 2022, 08:20:13 PM » Author: 108CAM
Or try to use a superimposed ignitor for HPS 50/70W lamps with the appropriate ballast. The 1.3kV may help to create an initial arc. But if you do this don’t hot re-strike the lamp with ignitor as then it can destroy the resistors of the starting probe or even form an arc in the outer bulb (as happened already on one dead Philips lamp with a 4kV ignitor)

I did revive may old dead lamps in that way with success.
Just bumping this up because I don't know for sure what "superimposed ignitor" means. Would still like to revive the lamp
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Re: Reviving a 50w MV lamp with an 80w ballast « Reply #6 on: August 05, 2022, 02:42:26 AM » Author: Medved
Superimposed ignitor is a type of ignitor, which essentially has a HV generator output in series with the lamp. So by that the main ballast output is connected in series with this HV generator output, so their voltages sump up, aka "superimpose". The "HV generator" is in fact the secondary winding of a step up transformer driven by a pulse from the pulse circuit. The transformer works only for narrow / high frequency pulses, for the mains frequency operating current it forms essentially a short circuit (because of its rather low inductance).
An example is here .
The main benefits are first the main ballast with its dense winding is not exposed to the HV pulses, only the wire between the ignitor and lamp is. It is way easier to make the rather small HV transformer in the ignitor to withstand the high voltages, than the whole bulky and mainly hot main ballast assembly. So beside higher reliability (the hot ballast is not exposed to high voltage, while the ignitor operates at rather low temperatures because there is not much wire resistance passing the lamp current there) it allows for really high voltage ignition pulses (7kV were quite common for HPS in the 80's here). And the rather small ignitor does not have to be physically placed with the ballast, so could be with just the lamp, so allows large distance between the lamp and the heavy ballast, without that long cable affecting the ignitor performance, the rather small and lightweight ignitor is placed with the lamp and the cable between the ballast and ignitor is going the long distance. The disadvantage is, because the HV secondary has to be of low impedance for the main operating current, its inductance is limited, so it can generate only rather narrow ignition pulses. That means the distance between the ignitor and lamp is really limited then. This could be countered by operating the ighnitor at HF AC bursts, but that then makes the "pulser" part way more complex.
Other advantage is, one ignitor type may easily serve wide range of lamps, the only limits are the maximum arc current (as it has to pass the HV transformer secondary in the ignitor, but usually the rating uses to cover rather high currents) and the peak voltage it generates (so if it is "HPS  only" with its 1.5..2.5kV range or "HPS and MH" with its 3.5..5kV range). So with just barely 2 models you may cover practically all range of lamp types in use. However the ignitor type is quite tied to the operating voltages (ballast OCV and arc voltages), but for 230V series choke markets this is not any issue, as the OCV is 230V and the arc voltages in the 70..140V range everywhere. This simplified logistics (2 ignitor types are good for dozens of lamp types) is the reason why it is the primary choice in the "230V all series choke" (Europe,...) markets, even when it is a bit more complex (it needs its own transformer...) than other types.
In the "115V" markets (North America,...), because there the lamp arc voltages vary a lot (mainly the HPS), so essentially each lamp type would require a dedicated ignitor type, so their a bit higher cost makes them way less popular (till virtually non existent) there.

Compare to that there are "semiparallel" ignitors, which are in fact a LV pulsers connected to a tap of the main ballast, using the ballast winding as the HV pulse transformer. Because the main ballast winding is a low frequency coil, this means the HV pulses could be rather wide and slow, so tolerant towards higher capacitance (so longer cable) of the connection towards the lamp. Plus the ignition energy is greater, which may help with ignition of some lamps. But the drawbacks are, because the main ballast is part of the ignitor functionality, it has to be integrated together with it and the main ballast winding gets exposed to the high voltage. Because it uses the main ballast winding in function of the HV transformer, it is cheaper to make, so became the main choice whhat is used inside of the North American pulse start ballasts. In

And to complete the list. there are "parallel" ignitors, which are 2-wire devices connected just plain parallel to the lamp. These are simple to connect, but must generate all the ignition voltage inside of them, plus expose the ballast to the ignition voltage as well. On the other hand there is no component exposed to the arc current during the runtime, it becomes quite handy for really high power lamps (700W and above), mainly when many of these use to suffice with lower striking voltages (because the rather low buffer gas pressures). This type is used mainly when low ignition voltage is sufficient, or where the ignitor output power has to be rather high (to warm up electrodes in cold cathode mode), mainly with LPS lamps.
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Re: Reviving a 50w MV lamp with an 80w ballast « Reply #7 on: August 05, 2022, 05:00:15 AM » Author: 108CAM
In simple terms do I just hook up the ignitor as if it was a HPS circuit? That's the question I need answered.
This is something I've never tried and I want to be certain that I get everything right.
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Fluro starter chimes combined with a 50hz ballast hum and blinking tubes is music to my ears.

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Re: Reviving a 50w MV lamp with an 80w ballast « Reply #8 on: August 05, 2022, 08:58:33 AM » Author: Medved
Yes, exactly...
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Re: Reviving a 50w MV lamp with an 80w ballast « Reply #9 on: September 22, 2022, 08:55:01 PM » Author: 108CAM
I finally decided to try and revive my dead 50w MV lamp by means of adding a 35w HPS ignitor to the circuit and even though the lamp struck, the mercury didn't vapourise and the lamp remained pink instead of warming up and turning white. I let it run for about 5 minutes and that's all it did. The lamp didn't even get warm to the touch and it still won't strike on it's intended gear. I'm still deciding if I want to try it again and let it run longer.
Here is what happened when I tried it.
« Last Edit: September 22, 2022, 09:19:58 PM by 108CAM » Logged

Fluro starter chimes combined with a 50hz ballast hum and blinking tubes is music to my ears.

Rest in Peace Electronic Lamp Manufacturers of Australia
1925-2002

Bring back the AJF Zodiacs!

Total incidents since joining LG: 11
Lamps accidently broken or smashed: 9
Ballast explosions/burnouts: 2

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