Transformer Going Up In Voltage Over Time

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I have a transformer from a 1953 jukebox that seems to be increasing in voltage over time. When I first got it, it was outputting 32V. A week later it seemed steady at 38V, then 45V. Now I just measured it and it’s at 50V.

I see no visible signs of burning or excessive heat and I’ve not seen or smelled any smoke.

It is supposed to be a 115V => 32V (approx) transformer.

What is going on? Do I need to throw this thing out?

voltagetransformershareedit  follow  flag asked 3 hours agoDicer101 New contributor

• 1I guess that could happen if the primary windings were shorting out one-by-one. I don’t know how likely that is. Are you testing the transformer by itself or is there a circuit connected to it? – user253751 2 hours ago 
• 1Check the battery in your multimeter. Seems like it might be going flat. – brhans 2 hours ago
• 1Could it be old/weakening battery in the DMM causing incorrect measurements? As a test, if you measure a AA battery and instead of 1.5V it reads 2.3V, that’s the problem. – MarkU 2 hours ago
• 1Welcome. Are you tracking the AC input voltage as well? This can and will vary with time. – VTNCaGNtdDVNalUy 2 hours ago
• 1What kind of DMM are you using to make these measurements? Some very low quality DMMs are not rated for measuring 110VACrms line voltage safely. Peak 110VAC voltage is more like 170V peak. And 48V DC is considered the highest “safe” DC voltage. – MarkU 2 hours ago
• 1Wow – those were fast responses! To answer some of your questions: – The DMM is an Equus 3320. Will replace batteries and see what that does. – The transformer is in a circuit, though I can easily isolate it. Will do that and make sure I’m getting the same results. Thanks everyone. – Dicer 2 hours ago 
• @Dicer, Many thanks for starting an interesting discussion on a1953 transformer, and how to troubleshoot it using a 1990 DMM. You bring back my sweet memories decades ago, of going to metal gear shops, buying laminated iron plates, copper wires, DIY a 200VAC to 24VAC transformer, and learned things like induction, eddy currents etc. Fast forward a bit, I am now happy to use my kitchen induction cooker which I think is using eddy current to cook my eggs etc. Cheers.. – tlfong01 26 mins ago   

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