12V G4 Lighting Flickering and Transformer Overheating


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Old 06-12-20, 04:57 PM
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12V G4 Lighting Flickering and Transformer Overheating

Hello everyone,

I have been having an issue with a strip of (8) 12V G4 LED lights that begin flickering after several minutes and causing the transformer to overheat. This strip of G4 lights were originally halogen, but I replaced them with Philips G4 LED bulbs that are supposed to work in fixtures that are originally meant for halogen bulbs.

I installed a new transformer that steps down 120VAC to 12VAC. The transformer is a General Electric LET-60-LW. This transformer was described as designed to handle halogen and LED lighting. It has a minimum draw rating of 3.0W and a maximum draw rating of 60W. The G4 LED bulbs I am using are rated at a power consumption of 2W each, and I have (8) G4 bulbs so that would be a total of 16W, which meets the minimum draw rating and is well below 80% of the maximum draw rating.

I checked my wires and the connections, and I cannot find any faults or issues. This transformer consists of (4) wires of which (2) are blue that go to the light fixture's wires and the other (2) are the hot and neutral that go to the feed of power.

I changed the wires I used to make the connection and redid my connections, but the issues persist. I also bought another new transformer of the same type to see if the issue was the transformer, but the new transformer also became too hot and the lights eventually started to flicker. I used a multimeter to measure the voltage at one of the G4 sockets, and it was rather low. I expected the reading to be around 12V since that is the output of the transformer, but my multimeter's readings are about 0.030V. It is possible I incorrectly measured the voltage. I also noticed that the LED bulbs are becoming hotter than they should be. I am not sure how to go about troubleshooting and diagnosing to find out what is causing the issue. What should I check for both physically and with the multimeter to find the issue?
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The Layout
 
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Old 06-12-20, 05:44 PM
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LEDs operate on DC voltage, not AC voltage directly from a transformer as shown in your diagram. 12 VAC has a peak voltage of 17 VAC. This is why the circuit is getting hot. You need to add a rectifier between the transformer output and the LEDs or get a 120 vac to 12 vdc, 30 watt minimum power supply.
 
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Old 06-12-20, 06:31 PM
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I agree.....many of those LED replacements are DC only.

Converting a 12vac transformer to DC via a full wave bridge rectifier will yield near 17vdc.
Probably best to get an actual 12vdc switching supply.
 
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Old 06-12-20, 07:34 PM
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This is what I had thought could be the problem, but the packaging for the light bulb specifically states that it is intended for use with low voltage electronic transformers with AC output. The packaging further states that it is not intended for DC operation. However, it does state that it is not compatible with all low voltage transformers.

The transformer I bought has AC output and a low minimum load of 3W and it stated that it is compatible with most LED bulbs. It seems though that this transformer may not be compatible with this specific LED bulb. This leads me to wonder what kind of 12VAC transformer is compatible with these bulbs. Fulham offers a transformer that has an AC output and a minimum load of 10W so it will work for my situation, but I do not have any way of knowing that it will be compatible with this bulb.
 
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Old 06-13-20, 04:14 AM
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All LEDs are diodes and conduct current only when the anode is positive relative to the cathode. This only occurs 50% of the time with a sine wave AC voltage. I am not sure what the LED manufacturer means when he states to use an electronic transformer. I think what you have is a magnetically coupled transformer. Call the LED manufacturer/distributor and ask for a transformer brand and model# compatible with their G4 LEDs.
 
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Old 06-13-20, 07:34 AM
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Hi, what bulb did you purchase, post a pic of the specs, that voltage reading sounds odd, what type of meter and what did you have it set on, did you take the reading with no load ?
Geo
 
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Old 06-13-20, 04:57 PM
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I purchased the Philips LED CorePro capsule bulb that is a halogen T3 replacement with a G4 Bi-pin base. I have attached pictures of the bulb in the packaging, the back side of the package, and the specs of the bulb from the Philips information leaflet. The multimeter I used was an AstroAI brand that handles most functions of testing, and I had it set to VAC. I took the reading while there was a load of 14W. I removed one bulb while the system was on and tested for voltage at the socket.

I just tried a different 12V transformer (LET151) and left it on for about (1) hour. It did not get hot or even warm, and there was no flickering at all. I don't understand why this particular transformer I just used worked fine. It is made by the same company and outputs 12VAC just like the original transformer. It has a higher maximum wattage rating of 150W instead of 60W like the original. I do know this transformer that I just used was an older one. It seems that the transformer I just recently used (LET151) is compatible with these bulbs, but the one I originally used (LET-60-LW) isn't for some reason.<img src="https://cimg1.ibsrv.net/gimg/www.doityourselft.com-vbulletin/2000x1156/specs_dcbfd0492d0de693081bd4a36d3ee476d22714ee.jpg" width="2000" height="1156"/>
<img src="https://cimg3.ibsrv.net/gimg/www.doityourselft.com-vbulletin/889x500/dsc_0011_resized_cacd1640b3b30e46bd8d5cf6054f888032386c35.jpg" width="282" height="500"/>
<img src="https://cimg7.ibsrv.net/gimg/www.doityourselft.com-vbulletin/800x450/dsc_0013_resized_daa794934f72cf5e880891e730f89907e26d6168.jpg" width="800" height="450"/>
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Original 12V Transformer
<img src="https://cimg9.ibsrv.net/gimg/www.doityourselft.com-vbulletin/889x500/dsc_0017_resized_f6b019b7ff6deab5a1990f86fd2c2af9a8f800e2.jpg" width="282" height="500"/>
Properly functioning 12V transformer
 

Last edited by Xenzo; 06-13-20 at 07:22 PM.
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Old 06-14-20, 04:38 AM
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Hi, according to warning on the label it seems only use with electronic power supply.
Geo

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Old 06-14-20, 03:45 PM
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I noticed that warning too, and I checked the packaging for the original transformer I was using and it states that it is fully electronic. I have attached a picture of the packaging for the original transformer. That had lead me to buying a second one thinking the first one was defective but the second one also overheated and caused the lights to flicker. The transformer I am using currently is working properly, but I just don't understand why this one works properly and the original one doesn't. I did have someone tell me to watch the amperage output rating of the transformer, but I thought that the amperage output was used as needed by the lights.
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Old 06-15-20, 02:06 PM
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Interesting the input voltage has units of VAC while the output has units of V on the preceding package. Have you measured the output voltage with a multimeter? The backward RU symbol only indicates 1 or more of the components inside this power supply have been UL tested, but not the whole device. UL would never approve a device containing a "Caution-Risk of electrical shock" statement on the device. Interesting it will not operate below 3 watts. It must be the short circuit protection components only operate above that power level.
 
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Old 06-15-20, 07:53 PM
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I measured the output voltage of the original transformer by using a multimeter set to VAC and pushing the probes into each side of one of the G4 sockets while the system was turned on. I turned on the lighting system and removed (1) G4 light bulb and then tested for VAC at the empty socket. I was not able to directly test the voltage of the transformer while it was on and nothing loaded to it since this transformer will only activate unless there is a minimum load of 3W. I tried testing it that way regardless, and there was no reading. When I tested at the socket while the system was on, the reading was quite low (about 0.03V). I only tested for voltage with the original transformer and did not try this yet with the new transformer that is working properly.
 
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Old 06-17-20, 03:32 PM
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A single LED will only illuminate when the anode is positive relative to the anode. An LED lamp consists of hundreds of LEDs connected in series or parallel or both (depending on the lamp manufacturer) and therefore can operate from AC or DC or both depending on the configuration. If the circuit consists of multiple LED lamps, this affects the size of the power supply because the multiple LED lamps can be in series or parallel. Because of all these variables, an LED lamp circuit requires some engineering. In my opinion, the LED lamp manufacturers are not currently providing needed information to be successful. Using LED lamps from different manufacturers in the same circuit will lead to failure.
 
 

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