Emulator won't strike

I'm having a strange problem with one of my Emus. I've tried it with both a brand new HOLL-1000 lamp, and a slightly used one that works perfect in another fixture. You can see the lamp try to strike multiple times, the igniter doesn't seem to have a problem creating an arc in the lamp, but the lamp never actually holds the arc for more than a split second. It's almost like the power supply can't supply enough current to keep the arc stable.

Has anyone experienced this issue before? What did you do to resolve it? I haven't used this fixture in some time because I couldn't afford to replace the lamp for a while, but just recently got replacement lamps in, and now I'm having this problem.

Any ideas?

Jeff:dunno:
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    I realize that this is late for the first poster, but the Emu lamp PS is really not much more than a dimmer in a lot of ways, which is regulating lamp power. The four SCRs SC1 - SC4 are a basic bridge rectifier, just made up of SCRs so that it can be controlled, and the drive for that is from IC6. (This is on page 3 of the schematic). Control comes in via P13 and thermal cutout TH1, and IC4 is a multi stage voltage comparator that determines what is being commanded - shutoff, low, or high intensity. T4 determines run/off, and IC1, IC3, T3 and T1 sense lamp voltage and provide control feedback accordingly. This feeds the ignitor section (schematic page 2), and it would appear that unless power is seen from the supply (B+ line), that the comparator in IC2 will not allow the ignitor to fire. So, looks like if you are seeing an ignitor pulse that the supply is at least trying to run. The cap (unless shorted, then I think the fuse would go) would not put AC on the output, only half wave DC. If you truly see AC on the output, then likely one of SC1 through SC4 has failed. Otherwise, if feedback in the power supply has failed (IC1/IC3,etc) then it may not come up to voltage under load, not sustaining an arc. All in all, there are a pretty simple design, once you figure out what it is doing, which is what I have tried to detail here. No high voltage either, just so you stay on the card, so should be pretty easy to probe around and find the problem.

    One of mine would not lamp off, and a change of IC4 (very cheap part) cleared it right up.

    Oh, and if you think of an SCR as a controllable diode, you will pretty much have the concept . . .

    - Tim
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  • 0
    I realize that this is late for the first poster, but the Emu lamp PS is really not much more than a dimmer in a lot of ways, which is regulating lamp power. The four SCRs SC1 - SC4 are a basic bridge rectifier, just made up of SCRs so that it can be controlled, and the drive for that is from IC6. (This is on page 3 of the schematic). Control comes in via P13 and thermal cutout TH1, and IC4 is a multi stage voltage comparator that determines what is being commanded - shutoff, low, or high intensity. T4 determines run/off, and IC1, IC3, T3 and T1 sense lamp voltage and provide control feedback accordingly. This feeds the ignitor section (schematic page 2), and it would appear that unless power is seen from the supply (B+ line), that the comparator in IC2 will not allow the ignitor to fire. So, looks like if you are seeing an ignitor pulse that the supply is at least trying to run. The cap (unless shorted, then I think the fuse would go) would not put AC on the output, only half wave DC. If you truly see AC on the output, then likely one of SC1 through SC4 has failed. Otherwise, if feedback in the power supply has failed (IC1/IC3,etc) then it may not come up to voltage under load, not sustaining an arc. All in all, there are a pretty simple design, once you figure out what it is doing, which is what I have tried to detail here. No high voltage either, just so you stay on the card, so should be pretty easy to probe around and find the problem.

    One of mine would not lamp off, and a change of IC4 (very cheap part) cleared it right up.

    Oh, and if you think of an SCR as a controllable diode, you will pretty much have the concept . . .

    - Tim
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