Elmo GS1200 electrical issue

[Steven J. Kirk]

Okay, so I have a GS1200 that trips the household circuit breaker after only 30 seconds or so when switched on. I'm in the UK so it is 240volts. The machine is the correct voltage and the transformer is set to 240v. I'm imagining an Earthing problem but does anyone have any ideas where to start. Is it something simple that comes up with these machines?

[Steve Klare]

Hi Steve,

It's interesting that you trip the panel breaker yet the much lower value fuse inside the GS seems to be weathering the storm.

Here a normal household breaker is sized to provide something up to about 1800 Watts, and yet even the Xenon GS is fused to allow only 450W. Somehow you have an excess of at least 1350W flowing in and still not blowing that projector fuse.

That's a lot of power and most likely a lot of heat. What's a hair dryer or a waffle iron, like 1500W?

What I would do in your position is operate the thing for that 30 seconds and whether or not the breaker blows, stop and (please!) unplug.

Bearing in mind that things like capacitors store energy for a while after unplugging, run the back of your hand over non-metallic surfaces and feel where the heat is winding up (-not the lamp, that's a given!)

Based on the internal fuse seeming to stay intact, I'm a little suspicious of your line cord. If there was some developing internal short, it could conduct that excess current and leave the machine's fuse completely unharmed. The fuse is supposed to be the first thing inside the machine after the power inlet, so my wild guess is the power cord, the inlet it plugs into, or the wiring from there over to the fuse.

-Ohhhhh...you wouldn't happen to have a waffle iron plugged into the same line, would you? I love waffles, but they could be a problem here! (-just saying!)

[Steven J. Kirk]

Thanks for your input, Steve. That's right the fuses inside the machine are okay. The machine was a recent purchase as a 'spares' machine but I thought I would try to get it running. I suspect damp damage because the lens shows little spirals of 'fungus'.

[Ken Finch]

As Steve suggests, it could simply be that you have other appliances plugged in and on in that particular house circuit. In the U.K. most appliances have fused plugs. Of 13amps or less depending on the appliance. If this blows it also often trips the circuit breaker of that particular house circuit as well. You could check the projector lead to see if that is the problem as Steve also suggested.

[Steve Klare]

Hi Steve,

What you could try is kind of a layered approach to figuring out where the problems start.

1) Plug in the machine with sound. lamp and transport all turned off.
2) Wait at least 30 seconds.
3) Turn on the sound.
4) Wait at least 30 seconds.
5) Start up the film transport.
6) Wait at least 30 seconds.
7) Turn on the lamp.
8) Wait...you knowww...

When does the breaker pop?

If if pops before step #8, that's a smoking gun.

[Brian Fretwell]

As the internal and plug fuses stay OK, as you say, it looks like a current on the earth wire that is tripping the RCD. Perhaps a supression capacitor is leaking to earth the current building up in the 30 seconds it runs.

[Graham Ritchie]

Sounds like a dead short to me, of live mains voltage to neutral or earth, very dangerous in my book so be careful

[Steven J. Kirk]

Thanks guys! I suspect current in the earth. I will be careful and do some disassembly, all unplugged of course.

I have the service manual but was hoping someone would say 'Happened to me, just do this,' and give me a shortcut.

I have a extension cord meant for use outside with a cut off built in that I shall use too. Thanks again.

[Steve Klare]

I hadn't even considered the RCD angle. Here we call them Ground Fault Interrupts, and our Electric Code requires them to be installed only where there is a lot of water present, for example we have them in the kitchen, bathrooms and external outlets like out on the patio.

A ground fault would be some leakage between Hot or Neutral and chassis. Neither Hot or Neutral go very deep into a GS-1200. They go to the main fuse and a power switch and then the main transformer primary and get stepped down through the other windings to useful voltages for motors and amplifiers and lamps. The transformer also isolates these lines from ground and all the other circuits in the machine for user safety.

There is a Hi-Pot test done on electronics where they take Hot and Neutral and connect both to a high voltage source and connect the other side to chassis: to pass there needs to be minimal leakage current. Being that these have safety certification they should be able to pass this test too.

There is a GS-1200 Service Manual in this site's Warehouse section, and it has a schematic. There actually are no suppression caps on the primary-side circuit. If this is a ground fault situation, it may mean that there is leakage inside the power transformer itself, which is a bad thing that will only get worse.

Steve? Do you have an Ohmmeter?

When I do a resistance measurement on one of my own Elmo machines between line and chassis, it's just open circuit. Let's say yours is leaking something like a milliamp, which is borderline low, you should see 240Volts/.001Amps=240,000 Ohms. This is a little under a quarter of a Meg, not a whole lot. (Power Switch: "On"). You should be able to measure something like this with the average Ohmmeter. Mine for example will go up as high as 9.99 Megohms and is a good but not premium one.