followspot repairs and general questions about discharge lamps.

[ewanuno]

a friend of mine was given a load of equipment form a theater that was clearing out its warehouse.

 

one of the things we got was an old followspot

the people from the theater couldn't even remember if it worked.

we quite often hire a followsot so it'd be really nice to have our own.

 

given its age I wanted to give it a good testing before atempting to strike it.

 

I cant remember the model or manufacturer, but it has an external ballastwithout anything written on it, it is fitted with G22 lamp base

and a thorn 1kw cid 99-0222 lamp

 

how can I check that it's not going to go "pop!" when I turn it on?

using only basic equipment, ( a multimeter and a box of screwdrivers)

 

and what kinds of "pop!" are there? I have no idea what the failure modes for a ballast are

and could somebody point me to a good online descripion of what a ballast actually does?

 

obviously I cant test the lamp with a multimeter!

but how can I test the ballast?

 

 

I have a good history of maintaining conventional fillament lamps but this is the first time I got my hands on a discharge lamp.

 

and as you can see I'm a bit lost.

 

 

thanks.

 

ewan.

[adam2]

I would carry out a standard PAT test first to ensure that the article is electricly safe (though not perhaps functional).

Having ensured safety, the only real test is to plug it in and try it!

Remember that HID lamps can explode at end of life or if damaged, DONT be tempted to try it with any covers removed.

Remember also that HID lamps use very high voltages when starting, dont be tempted to poke around or test whilst live (unless of course you have suitable experience)

 

If the lamp lights but is very dim or flickers, or is a funny colour, this generaly indicates a worn out lamp and a new one should be tried.

 

If the lamp does not light at all, unplug, wait for five minutes* and then carefully examine the internals for blown fuses or loose connections.

 

To properly test the ballast is a specialist job, however use of a multimeter can give some indication.

Dissconnect the ballast from any other components and test between the "live in" terminal and the "live out to lamp/ignitor terminal" This should have a resistance of a few ohms or a few tens of ohms, a short circuit or an open circuit indicates a fault.

 

The ignitor can only be readily tested by substituting a known good one.

 

*Most HID lamp circuits contain capicitors, which can hold a dangerous voltage for some minutes after power off.

[SoLiEn]

Seconded for PAT Test, then assuming it passes, plug it in and try, make sure that everything is covered up first, and if it doesnt work, I personally would go away after unplugging it, have a cuppa or two, allowing 15 minutes to pass, then go back and take covers off. just my opinion, ** laughs out loud **, in this compensation culture society, I hasten to add common sense is king, and any actions you take are your own, not influenced by the members on the blue room. heh, been on a cover my arse course all week

[paulears]

external ballast with nothing on it? Best guess is a Strand 765. If so, it will have a big chunky connector on the ballast (or maybe a slightly smaller one, if it's the later version). The lamp house access is via the top with two twist to release catches.

 

The strike button on the unit will make a loud noise when you push it - quite normal. The PAT is a good move, but be aware that striking up involves a tad more than mains voltage, and needs a little extra common sense when poking around.

 

If it is a 765, then there a few reasons why it might no strike up. Lamp is the obvious one, but they are expensive and not too easy to find now. They seem to be made in small batches so getting them is a bit down to luck. I've a pile of these and can usually swap bits around to get them working, but I'm down to one good one now, so soon all will be out of action.

 

If, of course they are not 765s, then this post is rather pointless!

[Andrew C]

The easiest way to tell if it is a 765 is to look at the pic next to Paulears name above. That is a 765, usually in green.

[Wingwalker]

Looking at the original post it sounds to me as if its one of the original CCT units that takes both the CSI and CID lamps. PM me with a digital photo if you can and I'll have a look for you.

 

David.

 

 

P.S. Definately agree you MUST PAT test it first!!!

[Robe575xt]

I Agree with Wingwalker, sounds like an old CCT Sil 10 or a product from that range of fixtures. I have x2 of these units which are over 15 years old and still going strong, the units take a 1Kw CSI lamp but these are expensive. The ballast box usaually looks like the back end of the fixture where the lamp lives, i.e. finned to look like a giant heat sink for want of a better term. If you post a picture someone on here will confirm what it is.

[ewanuno]

I'll get some pictures up as soon as I can, just right now it's sitting in a friends garage, might not be real soon but I'll resurect this tread when I get my hands on it again.

 

it dosent look like the strand in paulears avatar,

 

but I do remember that the ballast looks like the back end of the case,

 

pat testing is a u.k. thing, I'm in italy but the idea is the same.

don't worry, I though that it went without saying.

 

I actualy found a few suppliers for the bulbs, not cheap though.

[paulears]

If you're in Italy, then it's a pretty important fact you missed out! Could be a number of makes popular there - Spotlihjt Milan made some interesting ones with 1K lamps and internal colour frames with no iris, but a zoom optics system.

 

I've added Italy into your profile as a location.

[ewanuno]

If you're in Italy, then it's a pretty important fact you missed out! Could be a number of makes popular there - Spotlihjt Milan made some interesting ones with 1K lamps and internal colour frames with no iris, but a zoom optics system.

 

I've added Italy into your profile as a location.

 

I don't think it's from spotlight, although spotlight is a good guess since they seem to have made 90% of the lights here.

 

and from what I remember there was an iris, zoom, but no internal colour frame.

 

sorry to keep you all guessing, but I'm touring next week and probably won't have time to take any photos for a while.

 

lets put the thread on the back burner and I'll revive it wahen I get some photos.

[ewanuno]

some pictures of the spotlight,which I recently got arround to photographing.

here on my picasa.

 

 

now I'm looking at them, my discription seems to have been fairly innacurate, my excuse being that the first time I saw it was in a dark warehouse.

 

 

anyway, Robe575xt, you said you have some experience with cct folowspots?

what kind of problems am I likley to expect??

 

 

I didn't plug it in yet beause I've been away performing and teching in a street theater festival in tuscany,

where there was never enough electricity and everything was on 10a italian domestic connectors.

 

 

my plan is as follows,

 

1. good visual inspection under good lighting conditions!

2. change the cables, or at least shorten the cables to get rid of the worn sections at the ends.

3. test for earth shorts and shorts to neutral (we don't have pat testers in this country.and theres a strange lack of green stickers on everthing)

4. test the balast as adam2 suggested

5. turn on from a safe distance

6. strike it with a long wooden stick

 

if 6. dosent work, I'll probably continue striking it with long woden stick untill my temper calms down, or maybe try to find a known good bulb.

 

any other advice? other than flying to the u.k. to have it pat tested?

(theres not any subtle details to the pat test that I'm missing are there? it just has to not endanger the user or the supply, right?)

[Andrew C]

(theres not any subtle details to the pat test that I'm missing are there? it just has to not endanger the user or the supply, right?)

Definitely CCT.

 

The two things that are really important when PATing this will be a good visual inspection, especially inside the connectors and test the quality of the earth bond all the way to the lantern. With a PAT test box, this test would be done with twice the fuse current, up to 25A. The purpose of this is to stress the earth cable to show up damage that hasn't completely broken the core. For example, if you just test with a multimeter, one strand of the earth wire will give you continuity, but very little protection in the event of a problem. Normal pass level would be 0.1R, but the ABTT book suggests that 0.5R is more realistic for lanterns.

 

Follow spots would be considered fairly high risk as the operator will be holding it all the time in operation.

[ewanuno]

(theres not any subtle details to the pat test that I'm missing are there? it just has to not endanger the user or the supply, right?)

Definitely CCT.

 

The two things that are really important when PATing this will be a good visual inspection, especially inside the connectors and test the quality of the earth bond all the way to the lantern. With a PAT test box, this test would be done with twice the fuse current, up to 25A. The purpose of this is to stress the earth cable to show up damage that hasn't completely broken the core. For example, if you just test with a multimeter, one strand of the earth wire will give you continuity, but very little protection in the event of a problem. Normal pass level would be 0.1R, but the ABTT book suggests that 0.5R is more realistic for lanterns.

 

Follow spots would be considered fairly high risk as the operator will be holding it all the time in operation.

 

so really I have to replace the cable, don't I?

I can't see any simple way of testing the cable under a 25a load. short of creating a delibireate short to live and seeing if the cable melts before the breaker trips? that seems a bit dangerous!

[Andrew C]

so really I have to replace the cable, don't I?

I can't see any simple way of testing the cable under a 25a load. short of creating a delibireate short to live and seeing if the cable melts before the breaker trips? that seems a bit dangerous!

You SHOULD then test the new cable; so replacing it won't help per-se. The PAT test used a low-voltage high-current test for the earth bond, and NOT mains!

[ewanuno]

so really I have to replace the cable, don't I?

I can't see any simple way of testing the cable under a 25a load. short of creating a delibireate short to live and seeing if the cable melts before the breaker trips? that seems a bit dangerous!

You SHOULD then test the new cable; so replacing it won't help per-se. The PAT test used a low-voltage high-current test for the earth bond, and NOT mains!

 

 

wow, I wish we had pat testers here, thats sounds great, it'd be really nice to know when I had a good earth rather than just an earth.

 

I guess I'll just replace the cable and skip the extra step I SHOULD be doing. (I thought that pat testing was not required for brand new things? my knowlege of pat testing is all heresay anyway)

 

and the starter? it seems to be located in the fixture. is a starter problem likely? I'll open it up and check the connections anyway.

 

just to clear up any confusion, yes it definatly is a 1kw cct silhouette.