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Author Topic: testing a T14/1 for continuity without damaging with DC  (Read 3142 times)

jackreynolds

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testing a T14/1 for continuity without damaging with DC
« on: July 15, 2014, 09:49:52 AM »

Hi Guys

I have a quick question about testing a T14/1 transformer for continuity without damaging the windings or magnetising the core.

Are there safe ways of doing this? I guess a DMM set to continuity but i am rather wary of damaging the thing so any advice will be gratefully received.

Thanks

Jack
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klaus

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Re: testing a T14/1 for continuity without damaging with DC
« Reply #1 on: July 15, 2014, 11:02:14 AM »

No damage that I can think of. Don't set your meter to continuity, but ohms.
Depending on what era T14/1 you have, here are the DC-resistance ranges:

Primary: ca. 3.1- 3.3 kΩ
Secondaries (each): ca. 30Ω
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

jackreynolds

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Re: testing a T14/1 for continuity without damaging with DC
« Reply #2 on: July 15, 2014, 11:40:17 AM »

Thanks klaus. I have a decent meter so it should be ok then. I just know some meters put out 9VDC to test for resistance, which i thought might damage the coils.

Is the DC resistance the best way to date a T14?
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jackreynolds

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Re: testing a T14/1 for continuity without damaging with DC
« Reply #3 on: July 15, 2014, 11:42:18 AM »

I'm also looking for someone to restore an old C12 in the UK. Do you have any recommendations over here?
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klaus

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Re: testing a T14/1 for continuity without damaging with DC
« Reply #4 on: July 15, 2014, 12:20:32 PM »

I'm also looking for someone to restore an old C12 in the UK. Do you have any recommendations over here?

Maybe someone else has a recommendation. I don't.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

klaus

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Re: testing a T14/1 for continuity without damaging with DC
« Reply #5 on: July 15, 2014, 12:26:27 PM »

I just know some meters put out 9VDC to test for resistance, which i thought might damage the coils.

On "continuity" my Wavetek puts out 1.5 VDC, on resistance measuring setting 0.3VDC.
I cannot imagine that a transformer which has to absorb at start=up more than 150VDC on the primaries, could be damaged from such low voltage (and exceedingly low current flow).

Quote
Is the DC resistance the best way to date a T14?
No. You need to look at construction, lamination, labeling / print, color, type of lead out wires, etc. Post a picture, and we'll take a look at it.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

jackreynolds

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Re: testing a T14/1 for continuity without damaging with DC
« Reply #6 on: July 16, 2014, 06:18:05 AM »



The lettering is quite smudged but it appears to be a T14/1. The primary is just under 3 kOhms and the secondaries are both 30 Ohms. . All looks good so far. If you are able to give it a rough date that would be great.
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