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Old 24th March 2012, 08:36 PM   #11
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Also once the CT is identified it would be best to ground it to have reliable results.
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Old 24th March 2012, 08:39 PM   #12
kendt is offline kendt  Canada
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I am assuming the purple is the c/t. Its a beast of a transformer so i'd like to get it working
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Old 24th March 2012, 08:42 PM   #13
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if the resistance is such that the purple lead appears to be CT then go for it. Start grounding the purple lead and powering the transformer (variac and/or fuse on the primary). If nothing happens start reading voltage.
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Old 24th March 2012, 09:37 PM   #14
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Quote:
Originally Posted by kendt View Post
Ok here is what I get
rd/rd,yel 21ohm
rd or rd,yel across ppl 42ohm
yl/yl 8.0 ohm
rd/grn 2.5 ohm
all others 1.5 ohm
I guess I'm confused about your resistance readings.......

what does rd or rd,yel across ppl 42ohm mean?

If red to purple is 42 ohms and red/yellow to purple is 42 ohms and red-red/yellow is 21 ohms, then purple can't be the CT......unless I'm missing something.....

If purple is the CT, then some other pair needs to be 84 ohms....

although it sounds like end to CT =21 ohms and end to end is 42 ohms, which are reasonable numbers.
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Old 25th March 2012, 04:55 PM   #15
kendt is offline kendt  Canada
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I will double check those. I see your point.
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Old 25th March 2012, 05:09 PM   #16
kendt is offline kendt  Canada
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Ok after double checking it is the red/yel that is ct. Red to ppl is 42ohm, red/yel to either the red or purple is 21ohms.

So when i hook it up how do i know which is the primary??
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Old 25th March 2012, 05:42 PM   #17
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Ok, sounds like you got the CT figured out on the secondary. Is this a confirmed high voltage tube transformer (as opposed to a 12V or 18V etc secondary.)?

Red/yellow is a common CT color. Green is a typical heater winding (6.3V) and yellow is typical for a 5V winding for a rectifier filament.

What are "all others" above? Color and resistance? Are there any black or white leads? Do you have any idea what the secondary high voltage should be (roughly)?

Are there any other triples that are center tapped?

Do you have any other low voltage transformers? You may be able to use one to test this in safer manner than plugging into the mains. A variac is extremely handy for this. I've never used the lightbulb trick but it should work fine.

A picture would go a long way....

If you are using windows posting a pic is easy (I imagine that it's easy with a Mac too; I just don't know how to do that)

Snap a good close up picture, stick the camera card in the computer, right click on the pic and open with paint. Once in paint, click the resize button and shrink the image to say 40-50% of orig size, then save. Right click on the down-sized image and select properties to view the reduced file size. Once it's smaller than 200K, you can use the "manage attachments" button when you are posting to attach the pic here.

Edit: I just re-read your post 7 above. What are the resistances between the "other" colors and are any of them center tapped? Specifically any white, black, brown, blue........

White and black are common primary (mains) colors for US, Brown/blue are common primary colors everywhere (int'l).....Is the transformer old?

Last edited by boywonder; 25th March 2012 at 06:10 PM.
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Old 25th March 2012, 08:04 PM   #18
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What I would do is get a little 10 Volt AC wall-wart (10V or something near 10V). Cut the connector off the output wire. Jumper the wall-wart to the leads that you think are the primary wires. Measure the voltage of all the secondary combinations, multiply these readings by the ratio of line voltage to wall-wart voltage.
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Old 25th March 2012, 08:12 PM   #19
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Quote:
Originally Posted by boywonder View Post

Do you have any other low voltage transformers? You may be able to use one to test this in safer manner than plugging into the mains.
Quote:
Originally Posted by Speedskater View Post
What I would do is get a little 10 Volt AC wall-wart (10V or something near 10V). Cut the connector off the output wire. Jumper the wall-wart to the leads that you think are the primary wires. Measure the voltage of all the secondary combinations, multiply these readings by the ratio of line voltage to wall-wart voltage.
exactly...Kendt-Note that you need an AC wall-wart or other small transformer...DC won't work (obviously)
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Old 25th March 2012, 08:45 PM   #20
kendt is offline kendt  Canada
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Ok I here it is. Thanks for the resizing tip. The yellow wires are the only ones showing any real resistance. 8 ohms. Everything else is pretty much 1 ohm

Could i use the dc to ac converter thats plugs into the cig lighter of my truck to test it?
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