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Hoffman Amps Forum image Author Topic: Help with Power Transformer voltages?  (Read 2359 times)

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Offline mini612

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Help with Power Transformer voltages?
« on: August 30, 2023, 02:06:52 pm »
To Admin ***I hope I'm in the right thread, if not, please move this or cancel it and I can post it in the right place***

I bought a box of misc old radio parts a few years back and this past weekend I dug through it to look for a PT for my new project.  Unfortunately, there was only one PT in the whole box!  It's physically smaller than the other PTs I have.  The PT has two black leads for primary, and secondary consist of two Red leads (no CT) and two Greens.  I decided to test it to at least know the values of the leads and the result is; Red leads = 172vac., and Green = 6.5vac.  I decided to to see if I could raise up the voltage a bit by using a full bridge rectifier with four 1n4007, and I got 156vdc.  I was a bit disappointed.  Without knowing any additional details of this PT, can someone tell me why I got 156vdc instead of something a little higher?

Thanks
« Last Edit: August 30, 2023, 02:18:34 pm by mini612 »

Offline sluckey

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Re: Help with Power Transformer voltages?
« Reply #1 on: August 30, 2023, 02:29:12 pm »
Put a filter cap across the bridge and the unloaded voltage will increase to 240VDC.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline mini612

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Re: Help with Power Transformer voltages?
« Reply #2 on: August 30, 2023, 02:45:52 pm »
Put a filter cap across the bridge and the unloaded voltage will increase to 240VDC.

OH YES!  Got it.  Thank you.

 


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