Gam Check

[zac850]

I have a gam check, and I just wanted to quickly run through the tests that it can do (and if I say something it can't do, please correct me.

1. test lamps (lamp check mode, it is a god send, i love it)
2. if you plug both ends of a cable into it, it will test cable continuity
3. it will check power coming out of a dimmer and tell you if there is an open ground or any other problem with the power


I am posting this in questions because i know it can do 1 and 2, but I am unsure about 3, and I am slightly hesitant into plugging it into my dimmers to test the power coming out of the dimmer (but I have a bad dimmer, so...)

Anyway, just wanted to make sure that the gam check can acutely test power coming out of a dimmer and I won't short anything out nor short myself out nor burn the building down.

 

[SteveB]

According to the GAM website: "Circuit tester checks if power is available, if polarity is correct, if wiring is correct".

It doesn't state if its power out of dimmer or not, though that's assumed.

The only problem is that neon and LED testers often won't allow the dimmer to fire, usually as they don't provide enough of a resistive load on the dimmer.

This state varies according to the type of dimmer, though. Newer SSR's and IGBT and reverse sine wave dimmers probably would fire. Older SCR's won't.

Thus I could never use a Home Depot cheapo neon 3 light circuit analyzer on my older dimmers. Haven't tried it on my new Sensors.

Steve B.

 

[zac850]

Yea, I guess going to there website would be a good place to go. It is strange, because I replaced the power cubes on the dimmers not to long ago, and this dimmer just stopped working. I am thinking maybe I accidently messed up the power-cubes when I installed them.

Another strange thing is that I had 2 instruments (twofered) that flashed on and off at its own will. I went to the dimmer, unplugged it, and found that one of the hot plug ends was corroded. It was coming off of a multi-cable, so I replaced the end of that multi with an extra multi end, but I have no idea what happened. I am going to order a new plug and get it wired on, but I'm just hoping it is not a dimmer problem. Is there any reason that the dimmer could haver caused this??? We're not overloading the dimmer (1150 watts on a 1.2k dimmer) and I have no idea why this happened.

 

[ship]

The gam check in addition to not being much of a resistive load might detect false readings such as open neutral when the dimmer is other than at full due to the nature of the check it's doing.


A true RMS ohms meter is the best way to test a dimmer given a resistive load on it.

Easiest way to do this is to get what's called a figure 8 which is a feed thru tool used to clamp amp probes to. Get the grounded one. You than do what ever form of plug you have adapting to Edison and from it and plug in something with a large filament as a load. I like 1Kw PAR lamps, but a 500w Fresnel is fine also. Goal would be to do something that's around half the capacity of the dimmer. Point the fixture at you so while you are testing, you can also watch the filament in physically seeing it glow in lower voltages.

In any case, the figure 8 has two holes in it to insert the probes from your multi-meter. A true RMS meter will correct for the chopped signwave that a non-RMS meter will not. The other option is to go analog - dial meter instead of digital multi-meter. They also will correct for the chopped dimming.

You than go thru the dimming range of the dimmer in watching it's dimming curve both voltage wise and by watching the lamp. You can also adjust the trim with this method.

 

[SteveB]

The cheapest way to use the GAM Check as a dimmer check is to wire it up in parallel with a resistive load.

When we tested thru all the circuits on a new system, we used a neon 3 lamp tester (basically the same thing as a GAM check - just a whole lot cheaper, but not as elegant and doesn't test lamp continuity) on a 2-fer with a 100w A lamp. Puts enough a load for the dimmer to fire the neon and give us a correct status.

This method was suggested to me by the authorized ETC service tech's from Litetrol Service, the company doing the commisioning.

A true RMS volt meter is also a good device to have around to actually measure the dimmer output voltage. Again it often needs a resistive load in parallel to get the dimmer to fire.

>Yea, I guess going to there website would be a good place to go. It is strange, because I replaced the power cubes on the dimmers not to long ago, and this dimmer just stopped working. I am thinking maybe I accidently messed up the power-cubes when I installed them.

What make of dimmer ?. Did you replace BOTH cubes ?.

> Another strange thing is that I had 2 instruments (twofered) that flashed on and off at its own will. I went to the dimmer, unplugged it, and found that one of the hot plug ends was corroded. It was coming off of a multi-cable, so I replaced the end of that multi with an extra multi end, but I have no idea what happened. I am going to order a new plug and get it wired on, but I'm just hoping it is not a dimmer problem. Is there any reason that the dimmer could haver caused this??? We're not overloading the dimmer (1150 watts on a 1.2k dimmer) and I have no idea why this happened.


Which hot plug end ?. The lead to the power cube ?. Is it a portable pack with 2P&G pin receptacles and male multi-cables as load feeds ?.

It may well be a dimmer as the load you describe is near at capacity. Running a load this close to dimmer rating can cause heating, though the connector is rated at twice the dimmer capacity. Could well be a loose connection at the hot pin of the male connector. Regular maintenance is a good thing, we open EVERY connector on portable cables, 2-fers, circuits and units EVERY year and tighten everything down (actually, circuits get done every 2-3 years as there not all in use all the time).


In the event it's a portable pack, or has a 2P&G receptacle, does a unit plugged directly into the receptacle work ?. That'll tell you if it's the dimmer or the multi.

SB

 

[SuperCow]

I've considered buying a GAM, but I'm a bit hesitant about the connector issues. At school, we have Twis-Lock connectors, but a lot of other places have Stage Pin connectors. If I buy one testing unit, can I interchange the plugs for it?

 

[ship]

Yes, you can interchange as long as you have adaptors. It's the same hot, neutral and ground just different plug. If in the case of twist at school and because twist would than lock your adaptors to the plug, I might go with it. Than again the stage pin version is flatter and fits into a tool box better. Also, other than in schools and theaters wired during the 80's, you won't find many places using a 20 amp L5-20 twist plug thus it's of limited value.

 

[avkid]

of three theatres i've worked in: 1 has stage pin, one Edison and the other twistlock(talk about confusing)

 

[SuperCow]

So, Ship, would that mean that I can interchange directly on the GAM, or do I have to add adaptors onto the already bulky testing unit? I agree, I would go for the Twis-Lock setup, but that would grow to something like two feet long with all the convertors. That's not exactly convenient to carry around.

 

[ship]

Companies like Advanced Devices/Bates, Rosco and other plug manufacturers make all in one adaptors for stuff like this. Forget who is making them, perhaps it's Union. I have a few I have acquired over the years but I never use them.

I don't use them because you are correct that they would be bulkey in exchanging something with flexible 18" whips as a normal adaptor for something that's say 6" long each but adding to a nine inch tester already without any flexibility to it once connected.

Your point is correct, I would be less likely to use one with adaptors on a ladder. While this is what I do in the shop in testing between 7 types of plug normally used by us, that's at my work table thus easier.

Given this, and unfortunately either invest in the twist lock one and buy a stage pin one later because that's most likely to be the one you will be using later in career.
Perhaps sell off the twist pin one when you leave the school. Or wait to buy one of these tools and use a multi-meter and Home Depot Edison connector checker with adaptor, until such a time you get into a situation that's going to last more than just a few years thus making the investment in one of these more useful. It's a large chunk of change to invest in a temporary need for it anyway.

 

[SuperCow]

I think I'll just try an convince my school to buy one. Shouldn't be all that hard, really. And then I can just take temporary posession of it until I graduate! At this stage, it seems like too much of an investment, especially since it's not universally applicabble.