Robe spot 250a. Blowing fuses

[OliB150]

Not sure if this is in exactly the right place, but I'm sure it'll get moved if not!

 

Anyway, I've got two robe colorspot 250at's out on hire at the moment and one of them has decided to blow a fuse or three for seemingly no reason. We suspected the lamp had gone and taken the fuse with it but when they changed the fuse it popped that one aswell.

Next thing we did was take the lamp out and try again, sure enough it started fine. We then put the lamp back in as it looked fine and sure enough again, it worked fine. We then got another night out of it but just before tonights performance it went again.

Taking no chances we have now replaced the lamp and fuse and it's working again.

 

Someone that works in the mover section of Stage said he thinks the original lamp is fine and just needs a few cycles on it to clean it up inside.

Now the main question is, do you think the lamp being in a slightly dirty state would cause the fuses to blow? Or is there something more serious going on inside?

 

Show comes down tomorrow and I'll be able to look inside and do any testing from then, but would be good to know if there's anything in particular I should be looking for in advance if this!

Ideally I'd like you to say it's just the lamp doing it, as I could do without being a mover down!

 

Thanks in advance and sorry if there's any typing errors, I'm on my iPhone and have aparently lost the ability to type properly on it recently!

[KevinE]

No simple lamp fault should really cause the fuse to blow, these are a discharge lamp and the current is usually limited to a safe level by the ballast. The lamp holder can physically short-out and no excessive current will flow.

 

 

First of all, dont run the fixture without a lamp. These are a discharge fixture and can be damaged by switching it on with no lamp present in the holder.

 

Funnily enough, I had exactly the same fault a couple of weeks ago. It was a very strange one; I could disconnect the feed to the ignitor (which is the way you can force the lamp to stay off safely) and the fuse would hold; I could disconnect the PFC cap and it would hold; but connect both and the fuse would pop.

 

It turned out to be a leaky mains filter. The combination of leakage through that, plus the addition of a working lamp circuit was enough to pop the fuse but not if operated independently.

 

If this isnt your fault, (and youve also ruled out the ignitor itself) then inspect the cables that carry the lamp current in the wiring loom. The insulation can rub through and either they short to the earth cable (which can also rub through), to the chassis or to other parts of the loom..with possible further damage.

[OliB150]

Thanks for the quick reply.

 

Thought it would be ok to run the fixture without the lamp, but point taken!

 

I'll check the leads first personally as it sounds easier to do, then I'll have a look at the other parts if that isnt the problem. If it is the insulation, whats a good long term fix for it? I assume simply using LX tape wouldnt be very good due to the temperatures inside...

 

On a quick side note, it does say in the manual that when the lamp blows it may take the fuse with it. But I got suspicious when we replaced the fuse and it went again, and then it turned out not to be the lamp anyway!

[KevinE]

If it's the lamp cables, they need to be replaced, they are a special cable that Robe UK can supply for a reasonable amount. They usually run through a silicone rubber sleeve that usually suffers as well!

 

Give them a tug to make sure they arent just holding on by a thread, they usually break in the most difficult to get place.

 

Discharge lamps are ignited by a blast of HT from the ignitor, with the lamp as its load. If there's no lamp (good or otherwise) present then the HT is free to wreak havoc whether by flashing across the lampholder or through to anything else it pleases! It happens rarely, but you wouldnt want to take the chance, would you!!

[OliB150]

Ok, I'll have a look at those then and give them a gentle tug!

 

Kinda annoying though, not long run out of warranty!

 

And ok, point really taken with the lamp thing, didnt really think much about it when I did it, just wanted to see if it worked without!

 

Thanks again for a quick reply, I'll post back with a final verdict just incase someone in the future has the same problem and uses the search feature (unlike me )

[david.elsbury]

Of course, if they are "on hire" as you say in your first post, are the hire company happy with you fiddling with the inside of your light? Or would they rather you return it to them for troubleshooting and repair?

 

Or did you mean that they are your fittings, and you have them out on hire to a client?

 

Cheers

[OliB150]

Hi, they are mine out on hire to a client. But I'm working on the same production so luckily I was there to help out. But obviously that won't be the case 99% of the time so I wanted to know what the problem is to fix it.

 

Thanks

[OliB150]

(double post I know, so sorry)

 

I have had a look inside these now and all the wiring looks fine from (what I think is) the ignitor to the lamp.

 

Could you inform me how to properly test the ignitor and the PFC cap please.

I do have experiance with electrics and moving lights, so should be able to understand most instructions.

 

Also, if it does turn out to be the ignitor, PFC cap or mains filter, do you know roughly how much these cost to replace? (Assuming I replaced them myself)

Thanks

[ceecrb1]

I reapair all the gear in our company..

 

The best advice I can give and have given many times, is this...

If you have more than one of the fixtures, just start swaping parts and retesting...

Once you swap a part over and the falt swaps to the 2nd fixture or is repaired in the first.... you´ve got it..

In this form little understandin or knowledge is needed but you can also proove things before you lay down cash on spares.

[OliB150]

Good point.

 

The only trouble is, the fault was a bit inconsistant. As we had the same lamp in at one point and it worked fine for about a day, and then not again. Since putting a new lamp in it seems to be better.

 

I may put the old lamp back in and see if it starts doing it again. Then if so, try your method of swapping parts. May need to invest in some more fuses before that though!

Also, I would need confirmation on which parts are which!

[Don Allen]

One possible reason for the lamp working one day and blowing a fuse the next day could be mains fluctuations. If the mains varies, it can change operating conditions which will allow the lamp to work ok or blow a fuse.

 

Substitution is a good troubleshooting technique but only change one thing at a time and in your case leave the swap in place for a day if you can, to allow for any variations in operating conditions.

[OliB150]

Only thing with that is surely it would have the same effect on both units. They were both on the same phase etc?

 

I put the old lamp back in last night and tried it, and it isn't a happy lamp. It tries to strike and illuminates, then turns off and the robe displays the "heat" error. I put the fans to high to see if it made a difference (I must add that it had all been switched off for over 2 hours) which it didn't. I then went into the menus and turned off the heat sensor thing, which made a difference, but only in the sense that the lamp didn't shut off. It stayed illuminated but at nowhere near the right intensity.

So is that lamp gone? I don't know how they react and if that is normal? It's now very black at the top of the lamp and the "core" is very silver. (I have pictures if it helps)

 

Sorry for the essay, but I figure that to help me effectively you need all the info!

 

Thanks for all the help so far!

[collism]

How about just relamping and then if it doesn't happen again problem solved! if it is still a problem then ignitor is always the most likely place to start.

[adam2]

This may seem obvious, but are the fuses the correct ones ?

Fuses slightly smaller than the correct one would work most of the time but blow more or less at random.

If the ballast has taps for different line voltages, is the correct one selected ?

Use of the 220 volt tap on a 240 volt supply will increase the current drawn, only slightly, not enough to blow the fuse straight away.

[KevinE]

The wiring from the ignitor to the lamp will be ok as its only a few inches long, I mean the wiring from the ballast to the ignitor, this is where it's more likely to go intermittent or break. If it's a broken wire, it can sometimes strike and maintain light for a while until it moves a bit; where it may go out and come on straight away, or go out and not restrike until its cooled. If that's the case, it will usually burn through in time and then be permanently off.

 

just a thought, it happens! This on-off cycling can also cause the lamp itself to fail permanently.