The PHILCO Phorum
116B-121 Output Transformer Replacement - Printable Version

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+--- Thread: 116B-121 Output Transformer Replacement (/showthread.php?tid=5170)


116B-121 Output Transformer Replacement - JWD - 09-09-2012

I am restoring an early 116B-121. In this radio the push-pull output consists of two 42's. The primary winding of the OPT is open and I am looking at possible replacements. The Hammond 125D looks like a good option. If I were to go with the 125D, secondary lugs 4&5 seem to me to be the correct choice to properly match impedance. Please let me know if I have selected the right Hammond replacement OPT, and proper secondary lug choice.

RE: 116B-121 Output Transformer Replacement - Ron Ramirez - 09-09-2012

Hi JWD

You want to match a 5,900 ohm impedance to a 1.25 ohm voice coil.

The 125D is a good choice as it can handle 10 watts of audio, which is what the 116B is rated at.

But you will want to use terminals 1 and 3 for your speaker voice coil.

This setup matches a primary impedance of 5,400 ohms to a 1.5 ohm voice coil, close enough for gubmint work. Icon_smile

Terminals 4 and 5 are meant for a 10K load to a 1.5 ohm voice coil, which would cause a more serious mismatch = loss of volume.

Details here:
http://www.hammondmfg.com/pdf/5c0054.pdf

RE: 116B-121 Output Transformer Replacement - JWD - 09-09-2012

Hi Ron,

Thanks for setting me straight. I was assuming a 10K output impedance based on some other reading I had done. I learned about the Philco Phorum from Bob Andersen's videos. This is a great resource.

Thanks Again,
John

RE: 116B-121 Output Transformer Replacement - Ron Ramirez - 09-09-2012

You're welcome Icon_smile

Also, take a look at the free file giving details on Philco speakers from 1929 to 1938 (including attached audio output transformers) - once unzipped, it is an Excel spreadsheet. Newly revised, now the top line remains stationary as you scroll down so you know the meaning of each column without having to scroll back to the top.

http://philcoradio.com/phorum/showthread.php?tid=215

Look for the file "spkrs.zip" in the link above.

RE: 116B-121 Output Transformer Replacement - AI2V - 09-11-2012

Would you like an original replacement? I've got the xfmr and all it needs is some cleaning and paint (hi-temp semi-gloss black is PERFECT for xfmr paint!). It's yours for the shipping. I'm trying to clean out my cellar.

Pete AI2V

RE: 116B-121 Output Transformer Replacement - TA Forbes - 09-11-2012

That's a nice thing to do!! You really do meet some swell people on this site!!