MAC 500 Partial Strike

[Daniel Cokewell]

Hey everyone,

I have a MAC 500 that, on top of a FBER which is most likely board related, only strikes the lamp partially (I know the FBER has nothing to do with this as it was working fine before with the FBER) By this I mean that I'll send the Lamp on command locally from the fixture, the relay clicks on, and the lamp begins to arc and continues to arc the gap in the lamp without forming the brilliant white light I should have. Instead I have a dim blue electrical arc. I've changed out the ignitor, lamp, temp switch, and the capacitor in the body, basically everything in the lamp circuit except for the Mains filter. I get the 230 reading from the outermost pins of the ignitor, I've tried a new ballast in the Circuit as well. Still, doesn't want to strike. my only remaining thought is that mains filter but I have no spares on hand to test them with, might result to frankenstiening an old fixture.
ANY THOUGHTS?

 

[chawalang]

Feedback Error is a common thing, I have toured movers for months on end flashing FBER and they have worked fine.

Have you checked your leads to the base and the base as well?

Was the initial lamp new? You said you swapped lamps but it the issue remains. Could be a bad batch of lamps.

Good old cruise ships they always have some form of antiquated equipment in the rig, when I was on it was old school cybers.

 

[icewolf08]

FBER or Feedback errors on the MaC 500 are usually due to misaligned hall sensors. Simple to fix by finding the little magnet and realigning it. Usually is it one of the gobo or color wheels that cause that issue.

Things I would try to figure out your lamp issues:
1) Check all your fuses
2) Are you using the correct lamp?
3) Place a known working lamp (from another fixture) in your questionable fixture. See what happens. If it works, you have a bad lamp or batch of lamps. If the problem remains, you have an issue in the fixture.
4) Connect suspect lamp to a known working fixture. Again, if it doesn't work properly, the issue is the lamp, if it does, then the issue is the suspect fixture.
5) Connect a known working power assembly (ballast, ignitor, etc) to the suspect fixture. If it works, you know you have bad electronics, if it doesn't work, you may have other control issues.

If the fixture can strike and maintain an arc, it would make me think that the issue is a lamp issue. Usually discharge lamps have to run in pretty tight tolerances or they don't work right.

 

[LavaASU]

Is it possibly sending strike voltage (the high voltage) but never transitioning to running voltage? I saw something similar happen with a followspot that would sent the strike voltage when we pushed the "emergency" ignition button but would not maintain the arc (after we stopped holding the emergency ignite) because the ballast was not outputting running voltage. Looking through the welding glass, this appeared a lot like what was described.

 

[Daniel Cokewell]

Definitely have been working on the feedback error as it was the original issue, then the lamp became my area of focus.. returning to the feedback in a little while-
All excellent ideas. I've started with the lamp- multiple lamps even. they're all MSR 575/2 andfunction just fine inother fixtures but In the malfuntioning 500- no dice, won't play nice. I'm sure it would also be worth mentioning that this fixture suffered a short in the lamp circuit while on the bench metering between contacts on the temp switch. Ithe first thing I did was try a new temp switch since that was the most local component involved in the short, didnt fix it. Wolf- I've taken all of your instructions to heart trying to isolate the problem, new lamps, checked the conections at all terminals along the line of the Lamp circuit, Every lamp behaves the same...
Lava it sounds like you've got a grasp of my situation, and if the fixture is failing to switch over to that running voltage, where is that failure taking place. ballast yes, but I get the same result even when placing a replacement ballast in the line.

 

[JD]

Check the continuity of the lamp lines from the base contact back to the ballast. Movers move and therefore are always flexing the wiring. An open conductor may well let the high voltage pass (arcing over the break) while preventing any real current from flowing. This would be hidden by the wiring insulation.

 

[LavaASU]

Lava it sounds like you've got a grasp of my situation, and if the fixture is failing to switch over to that running voltage, where is that failure taking place. ballast yes, but I get the same result even when placing a replacement ballast in the line.

Sorry, I'm not sure on that. Possibly the electronics or whatever senses whether the fixture has struck. I'm not sure I've ever been in a Mac 500 (and if I have don't remember) so not totally sure where to point you.

 

[JD]

Quick 101 on ignitor circuits: The MAC 500 is available with a magnetic or electronic ballast, not sure which one you have, but...
On Magnetic ballasts, the run current is always there. The high voltage pulsing is done through a tickler winding in the core that causes high voltage spikes on the output. As soon as the lamp ignites, the output voltage drops and the circuit disengages. On electronic ballasts, an intentional high frequency flyback pulse is introduced to ignite the lamp. Once again, the run current is always available so the second the lamp ignites the current flows. Again, the output drop shuts off the starter circuit.
Since you have exchanged both lamps and ballasts, then we can be pretty sure something between the two is blocking the flow of current, thus the suggestion of checking wiring integrity.
Long shot- You may also want to check the line voltage going to the ballast with some form of load at the ballast end. There is always the possibility that a switching device (ex- triac or relay) has failed and that the voltage is dropping off when the lamp tries to strike.

 

[JD]

One added note of caution:
Never try to measure the output voltage of a pulse/ignitor ballast unless you like flying through the air or are fond of convulsions!
Ignitor pulses vary depending on lamp type, but range from 1,000 volts to 35,000 volts (xenon.)

 

[Daniel Cokewell]

Can't say that I've ever flown before, not like that at least and I'm not quite ready to experience a massive electric shock/ affibrilation of the heart- so I'll keep your words of caution close to my still-beating heart.
Thanks loads JD. I'll pull out the meter again and give it the good old college try! Your 101 got me thinking... Would the run voltage be enough to maintain the arc on the lamp, would it be enough to bridge the gap to begin with?

 

[Daniel Cokewell]

Quick note- I'm using magnetic ballast on all of my fixtures in the rig. Now onto the good stuff. After metering, I found that I do have continuity from both lamp base terminals right on down to the the mains filter. The ballast however gives me continuity only up to the Ignitor.. Should I be getting continuity right on down to the lamp terminals? the black wire stops right at the ignitor so its tough to tell

 

[JD]

In most cases, the Ballast assembly includes the transformer/ballast core, the ignitor, and the power-factor cap. It sounds like what you swapped was the transformer/ballast core only, and not the full ballast circuit. If this was the case, then there are two other parts in play: The power-factor capacitor and the ignitor module. Easiest way to check these is to swap them one at a time. Here's a little more on what they do-
1) The power factor-cap is usually in series with the lamp and is used to correct power factor errors. If this cap was weak or open, it would produce the symptoms you are having.
2) The ignitor can be one of two configurations. The first works by tickling a ballast winding to produce high voltage. (Sometimes know as a parallel ignitor.) If it failed, you would not be seeing any strike. The second is a larger module that contains it's own windings and uses these to produce the high voltage. (Sometimes known as a series ignitor.) These were more common in two piece units like the Satellite followspot (HMI) and almost all xenon followspots. Series ignitors should have a fairly low resistance across them (from the ballast to the lamp) and could produce those symptoms if the terminal from the ballast was open inside the package. Anyhow, enough theory! Just swap the modules from a known working unit and you should have your answer.

In either case, there is no real switching from Ignite to Run mode. The full current is always available and starts flowing as soon as the lamps successfully strikes and starts running.

 

[Daniel Cokewell]

OKAY. Like grinding away fingernails down to the flesh, I'm running out of ideas... and parts. I've exchanged every single part in the lamp circuit for a brand-spanking-new one and still No difference in the results. I didn't want to return until I had conquered the beast and could come back to the village with the severed head as proof but I'm still treading water here. If now I could mention one last symptom that may get some wheels turning- The starter (igniter) normally gives this nice resounding "BZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZT" when striking the lamp but this guy like to give me a condensed version of that which would sound a bit more like, " BZZT". I feel that the ignitor isnt getting enough of that voltage from the tickler winding in the core.

JD, You had mentioned checking the ballast with some form of load at the other end to see if the ballast is getting the right voltage. what would that test look like? how could I configure the ballast and which kind of load would you recommend and how would this all go together?

 

[JD]

Usually, a simple 100 watt light-bulb would work as a load and you would connect it to the Hot and Neutral lines feeding the ballast core. However, since you are running on 208/240 volts, the bulb would also have to be that voltage. (or two identical bulbs in series) The theory here is that when the ballast gets power, it should be getting the full line voltage. If there was a problem upstream, then you would get a much lower voltage or no voltage at all. Without the load, the voltage might read correctly as no current is being drawn. Don't have the wiring for the Mac in front of me, but the items between the line cord and the ballast usually include the power switch, a fuse, one or more thermal cutouts, and some controlling device such as a relay or triac which allow the fixture to operate without the lamp being on.
So, with the load attached, the bulb(s) should light as soon as the "lamp on" occurs (at the same time the fixture would try to strike.) Two outcomes are possible:
1) low/no voltage = problem before ballast.
2) normal voltage = ballast, ignitor, PF cap, lamp, or wiring.
Sure sounds like you have followed every option in choice [HASHTAG]#2[/HASHTAG]! The shortened "BZZT" might indicate the voltage is dropping as soon as there is any load. As a side note- just fixed a microwave oven this weekend that had all sorts of strange problems. Problem was a thermal cut-out that appeared to be ok, but as soon as the current was flowing it would go funky and start dropping voltage. Good luck! And let us know when you have the head of the beast!

 

[Daniel Cokewell]

Alrighty!
All issues on this fixture have been resolved. The original issue being the Feedback Error, was of course a bad PCB. so a spare fixed that thankfully. And the worst of the issues, not being able to lamp on fixture fully- taken care of. I was ready to chuck the thing off of the starboard side of the ship to live forever at the bottom of the Carribean Sea. I changed out the high voltage leads from the arm to the ignitor and that did the trick. That and I'm somewhat certain that the manufacturer has changed the wiring configuration of this particular ignitor from its old way so chances are that I had the ignitor wired wrong from the getgo. always double check labeling, lesson learned. This bad boy will be back in the rig soon! Thanks to all for your suggestions and comments!