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Toroidal Transformer Issue
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Toroidal Transformer Issue
robpiya
Hope someone can help me with an issue that just showed up.
I'm using a toroidal transformer for my power supply which has twin primaries so I can use it both in 110/230V countries. I had been using the transformer which was working fine in the US. However after traveling a long way to Nepal with the transformer in my luggage now a pair of the transformer primary wires are showing some resistance when I perform a DMM continuity test. The transformer has 4 wires on the primary side. When I check for continuity between the 4 wires one pair shows a value hovering around 040, however there is no beep. All other tests between the wires are showing no connection. When I hooked up the transformer to the circuit the power supply pcb did't turn on, so I immediately turned it off. I have a feeling that the transformer might have been banged up a bit on my travels. Is there a way to salvage this transformer or should I replace it with a new one?
Thanks in advance.
Graham Hinton
robpiya wrote:
Is there a way to salvage this transformer or should I replace it with a new one?


Replace it. Toroidal transformers usually have a kynar tape covering for protection, but this is easily pierced by dropping a tool on it or by tightening the transformer down over metal burrs or shavings. Some have an internal thermal fuse that is not replaceable. If you have no continuity just get a new one.

There are videos on Youtube showing how they are wound and which should discourage any thoughts of repairing one.
robpiya
Thanks Graham! Just hoping that the power circuit wasn't affected by the faulty transformer, fingers crossed.
Graham Hinton
robpiya wrote:
Just hoping that the power circuit wasn't affected by the faulty transformer, fingers crossed.


You could check for shorts between a primary lead and any secondary lead. If they are still isolated there should not be any damage downstream.

If you drop a screwdriver on a toroid or drop the toroid onto a sharp corner you can get a ding in the soft copper windings. It is most likely to break, but it might short two places on the same winding or between windings. It's strange that both your secondaries are open though. Is there any sign of damage or overheating?
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