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Subject: Re: Neon Transformer problems
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Date: 10/22/03 at 9:55 AM
Posted by: Mike Gray
In Reply to: Neon Transformer problems posted by Kyle Smith on 10/21/03 at 10:05 PM:
I am very concerned about your comment that you know nothing about electricity or electronics! It is not wise to "play" with things that could harm or kill you when you have little or no understanding of the safety issues. High voltage could harm or kill you. Please learn and understand proper high-voltage safety practices before you attempt to repair or use your transformer.
I would be remiss if I did not first warn you of the dangers of high voltage before giving advice about testing and repairing your transformer. Now, with that asside I'll suggest a few things that could be checked, but unfortunately transformers are usually not repairable. Neon sign transformers are potted with a a tough tar-like material that insulates the windings. Most neon sign transformers are quite simple in design. They are basically a transformer with a primary winding (A.C. mains) and a secondary winding (center-tapped and grounded high voltage winding). They also have a "magnetic shunt" which limits the short-circuit current to a safe value (usually the nominal value shown on the nameplate). If your particular transformer has any active regulator circuitry in it, then I can not help you without having a schematic diagram of the circuit. You can make two simple checks with an ohmmeter. But since you know nothing about electricity or electronics, you will need to find someone who does, so they could help you make these checks. The primary winding typically will show very low dc resistance (less than 2 ohms). The high voltage secondary winding will typically show something on the order of a few thousand ohms. In either case if the resistance is extremely high, or infinite, then a winding is open, and is not easily repairable. There is also a failure mode where the high voltage has arced either between windings or from a winding to the grounded metal enclosure or to the metal iron core of the transformer. In either case the transformer is junk! Also, make sure that the problem is not simply your power connections or your power source. You may be blaming the transformer as the failure when you actually have a bad connection going to it! A technician could take a voltage measurement at the primary power connection while the ciruit is energized. If there is voltage at the primary terminals, but no high voltage output, then you might as well consider it junk! From my experience, these transformers are not repairable.
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