|GamChek question is being discussed in the ControlBooth Lighting and Electrics forum; So I'm looking at getting a Gamchek for my tool box. But I just had a question first. At my ...|
Shawncfer (June 2nd, 2010)
line resistor to act as a dummy load so you don't get false positives from a dimmer rack. Remember, dimmer racks always have power on the line unless they have resistance. Those testers will always show that the circuit is hot.
The gamcheck does three things - cable continuity, lamp checking, and power testing. The three-lamp tester imaged above is similar to the power testing function (set to 'cable' and plugged in), but is not optimized for a dimmer - the gamcheck simulates a load - an in-line resistor - which the three lamp tester does not, the nature of sine-wave dimming makes the gamcheck superior for testing dimmed circuits.
And you wouldn't need a VOM to test the adapters for continuity - just plug the adaptors into each other and into the gamcheck, set to cable, and test the same way you would any cable. If this passes, then test a cable - if it now fails, then the cable must be the failing element.
And to be honest, I've never learned how to use one of those. But if I did, that seems a lot easier than a Gamchek
pigtail to the lamp. I would say that about 3/4 of typical failures involve either a blown lamp or a blown out socket. A power check is great to have, but lamp issues are most of the issue. If you want to save money, buy a stand alone lamp check and a stand alone power check. Build adapters for both and you are set. You lose the cable check but you can do that with a multi-meter fairly easily. I have a gamcheck at my theatre and use it all the time, however I own the "separate" route. I have had both testers for about 5 years and they still work.
Tester, Stagepin Lamp
Tester, Stagepin Power
Can you not check if its a blown lamp with a DMM???
tails long enough to come around and plug into each other? And you have a set of these for each kind of connector? "Oops, I dropped my adapter. Now I have to test it again." That all sounds super convenient. And it'll cost around $100 for the whole awesome package!
...Just get a DMM. It does more. Travels in a much smaller package. And it'll force you to learn how to use the most basic theatrical electrician's tool after the C-wrench.
My $.02 (well, maybe that was like a nickle)
But now im in college, and yeah, next semmester I signed up for Physics. So hopefully I'll learn there. I needed a science credit, and what better science for my major?
A technology class at school is also a place to learn how to use a multimeter.
DMM vs GamCheck - let me see.
Using a DMM.
I'm at the top of a ladder trying to figure out why my instrument is not on. I get out my handy DMM to check for continuity in the lamp. My meter has a continuity check, so I turn the dial to that. Now I take one of the probes and hold it to a pin. Now I take the other one and hold it - opps - the first one slipped off. Let me try again. Ok - now I have them and it beeps so I have continuity. Let's check the dimmer. Change the setting to voltage. Stuff one of the probes into the socket find the other probe which has fallen down.
Doing a continuity check on a cable. Set the DMM to continuity. Hold the probe to one pin, and put the other pin in the female. Humm - no beep. Wait - did I put it in the right female? Ok now that I have that figured out, let me do it again for the ground and neutral.
Using a gam check.
Plug it into the fixture. That looks good. Now plug it into the circuit. Humm that was easy.
Cable check - just plug the cables into both ends of the gam check. Done.
My point being - time is money ( and aggravation). A gam check saves me time. Sure I could use a DMM and save a few bucks ( and I need one in my took kit anyway for other stuff). I could also hang lights without a scaffold from ladders, or do all my paperwork by hand and not using a computer, or haul lumber in my car instead of in a truck.
Sometimes the specialized tool is the right tool for the job.
Just my 2 cents worth.
Co-Creator of Plexus - a software only solution for controlling Conventional and Moving Lights
Glad I bought my Gam Check years ago, can't imagine the price of them today. My own Gam Check don't work so well these days in giving bad readings and I have not had time to find out why. Luckily someone from the shop is loaning me his. Concept of the Gam Check is good in being an easy test thing that does it's job well. No, I have never crossed electrodes to a DMM.. in melting them down, or loaned mine to an idiot that melted them down and I had to replace them. This much less having to have a full set of not just probes, alagator clips and other clips including insulation displaing clips so as to test stuff is a high task for a DMM. Handing up a Gam Check even with adaptors is easier. Same story on the DMM should you have quality probes in accepting to other types of probe - the above... 40' up on a ladder and you drop the probe? Pain in the rear in having done so but perhaps if removable probes as anyone that's anyone that uses a multi-meter has, yet they are easily removed and might more easily fall off if loose bananna pin or should it latch on something.
Multi-meter without removable bananna plug pins for changable options for the probe/clip? Never loan a multi-meter to someone that didn't at times arc the probes? In my view the Gam Check is an ideal and very safe tool to use. Also easier to tell the guy up on the ladder how to make it work in lamp check or power mode than explaining what the little symbols on the meter are.
Other ways to do this and even a early 90's ESTA article in doing so which didn't work out for me in doing. Still... Gam Check, great thing but very expensive. Adaptors are cheap. Were it me in buying one.. Stage pin is the current way, but twist lock in as above can be adapted from my stage pin don't work so well these days - and it aint from spread pins as the cause. Probably still say with stage pin as the norm but might consider twist or edison if I normally worked in such a house. Big fan of such a tool in my work box.
You do need a DMM immidately before a Gam Check by way of what you buy first, but the Gam Check is in not replacing it, also a good tool. Get the DMM first of course.
Last edited by ship; June 3rd, 2010 at 11:03 PM.
I agree with Ship. you should have both. Gam checks for fast trouble shooting of lamps on instruments, finding power issues, etc. DMM for everything else, really. A DMM will come with a manual on how to use it, read it and understand. Dont go sticking the probes into things that are dangerous, unless your qualified to do so, which, if you dont even have one yet, you wont be for a while yet. No big deal though, youll learn how to use them, and then discover that every outlet in your house is not outputting its nominal voltage rating. I have several of these gadgets, one of them has a pretty awesome current clamp too. I bought several extra leads, with lockable alligatory clips and some other jazz, to make working in the air easier. Get a DMM, then get a Gam Check, or make your venue buy one and use that, if your in HS or college and dont do much freelance. Overall, both are good to have.
Now shipping with industry standard 3-pin DMX.
ohm, 20 watt resistor across hot and neutral? Would that be enough load to get an accurate reading?
It would be about an 8.8 watt load on the circuit.
If not, how much load would you need to get an accurate reading?
(This is all theoretical of course. This shouldn't be attempted without the supervision of a licensed electrician. :D )
Sophmore - USC Upstate, Communications Major w/ Emphasis in Theatre
voltage, and for testing purposes that's the very thing we're trying to identify! Did you mean a 40W@120V (presumably linear) load, which would be .33A @ 120V, and therefore effectively 360Ω?
At any rate, the required load will depend what you're trying to do. For GamChek type purposes, 360Ω is quite excessive, since if the circuit is in fact working, that'd mean the little tester you're holding in your hand is now dissipating 40W. Hope you don't keep it plugged in too long. Plus you don't need to pull the voltage *all* the way down to "zero" for a simple "is the dimmer on?" type test. So for safety's sake, if you're designing a handheld tester, it's a good idea to start by looking at the maximum power your tester should dissipate within normal operational parameters, and setting that as an upper limit.
Working from the other end of the problem: A 120V neon indicator lamp (like those cheap little three light testers and GamCheks alike use!) has an initial breakdown voltage of ~95V. So lets say we need to hold the circuit's voltage below 80V in the off state to prevent false positives. The leakage current for the switching components in a dimmer is, from looking at a few datasheets for appropriately spec'ed parts, likely somewhere around 6-15mA. So using Ohm's law, 80V/.02A = 4000Ω. When the circuit is on, the resistor will dissipate around 3.6W. You could get that down a bit if you could find an indicator with a higher breakdown voltage, or add another component or two.
Hypothetically, of course
Last edited by ajb; July 7th, 2010 at 12:34 AM.