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Philco 91 Speaker Replacement - Printable Version

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Philco 91 Speaker Replacement - dconant - 10-28-2024

Hello, The speaker for my Philco 91 (cathedral) is shot. Coil is open and output transform is open on one side. The radio uses 1 8" speaker driven by two 42 tubes so it uses a center tapped output transformer. I am not having any luck finding another speaker so I think I want to try a modern speaker. If I do that can someone help me find a modern output replacement. I'm thinking I can replace the coil with resistor but not sure what wattage I would need. 

Thank you,
Dan

RE: Philco 91 Speaker Replacement - morzh - 10-28-2024

I would use a minimum 5W.

RE: Philco 91 Speaker Replacement - Brad Winder - 10-29-2024

If this is a radio you plan on keeping and listening to, I would consider using an appropriate sized inductor to replace the field coil. It will react very close to how the field coil does therefore allowing your power supply to give correct B voltages.

RE: Philco 91 Speaker Replacement - dconant - 10-29-2024

Well I like to do things the right way even if I don't plan on keeping it. Any idea what and where I could get such a thing as well as the output transformer?

RE: Philco 91 Speaker Replacement - morzh - 10-29-2024

Hammond is your friend.

RE: Philco 91 Speaker Replacement - Arran - 10-30-2024

Antique Electronic supply has filter chokes, and output transformers, as do some of the suppliers like Mouser, or Digi Key, the latter two usually being Hammond chokes. Then there is fleabay, but it's hit and miss. I think I would keep the original speaker, sometimes the field coils can be repaired, or rewound.
Regards
Arran

RE: Philco 91 Speaker Replacement - morzh - 10-30-2024

I used to rely in part on Play Things of the Past, but now it is Mouser.

In fact, Amazon also sells those. Same price, same shipping (not free even for prime members).

RE: Philco 91 Speaker Replacement - dconant - 10-30-2024

I did a quick look on Mouser. I don't have a clue what I am looking for. Can someone point me to the part I would need. My speaker coil is supposed to be 3275 ohms. Also how about the output transformer. That is center tapped with primary at 680 ohms and secondary for 1.25 ohm voice coil. I got this information from the speaker list some where on this forum.

Thank you,
Dan

RE: Philco 91 Speaker Replacement - morzh - 10-30-2024

125B or 125C, both would do. Same price. 125B is a bit smaller: see the mechanicals.

https://www.mouser.com/c/passive-components/audio-transformers-signal-transformers/?q=125&m=Hammond&type=Push-Pull
https://www.mouser.com/ProductDetail/Hammond-Manufacturing/125C?qs=N74Wby3oBT96Ia%252Bd9u2Zzg%3D%3D

You need that.
Do not get 125CSE - it is for Class A single-ended amps.


If you want an inductor for the filter, you could use this:

154E by Hammond
https://www.mouser.com/ProductDetail/Hammond-Manufacturing/154E?qs=NRA9IjDEzh0piIkDeDzf6Q%3D%3D

It is small.
If you find out there is no space, use a resistor.
I do not know what the resistance of the 1st field coil. I doubt it was 3.2kOhm as the other shown in the sch, but the DC resistance of the 154E is 1.67kOhm and you could add a small 1W resistor in series if you need to meet the higher resistance number.



PS. Do not take it as "buy" directive, do some research first. I only gave you some general pointers.

RE: Philco 91 Speaker Replacement - dconant - 10-30-2024

Thank you for you time.

RE: Philco 91 Speaker Replacement - dconant - 10-31-2024

I was wondering if I could use a more common Philco speaker and just add the resistance I need for the coil and get a new output transformer. My cone is pretty thin and fragile and the spider is distorted as well. This way I can have a speaker that will fit and look like an original.

RE: Philco 91 Speaker Replacement - RodB - 10-31-2024

Yes, I often have to substitute, then keep an eye out for an original. In the meantime, the radio is working and being enjoyed.

RE: Philco 91 Speaker Replacement - morzh - 10-31-2024

As Rod said, it is OK to use a fitting speaker, and then look for an original one.

If you buy a Hammond 125 output transformer, you could use just about any speaker and simply match the impedance by using the respective secondary taps of the 125.
If the field coil is too much, you can bypass it by paralleling a resistance; if too low, you put a serial resistance.
If you have a Philco speaker with the good transformer, make sure it is for P-P and the primary reflected impedance fits your output.

This said, if your speaker's field is good, send it for re-cone: you will have an original speaker with a new better cone. And it is not too bad price-wise. Sound Remedy in NJ, Rich Stamer, he does excellent job.
Of course, if your field coil is bad, then....

RE: Philco 91 Speaker Replacement - dconant - 10-31-2024

My field coil is bad. I am still hoping to find an original, but if I can't I will go with a fitting Philco speaker, 125C trans and resistor as needed for coil. I checked out the trans on the Hammond site and though that one will do. At this time I'm in no hurry.

I have restored several Philcos since retiring as a hobby (chassis and cabinet) plus other brands. Sad I have so many and don't listen to any of them. The only one I listen to is my Stromberg Carlson SR406 console at Christmas time.

BTW I checked Amazon for that trans and found it was 40.00 higher than Mouser. Gotta keep on your toes when dealing with Amazon.

RE: Philco 91 Speaker Replacement - morzh - 10-31-2024

From your text I am not sure if you intend to use the existing speaker with a resistor instead of the field coil.
It won't work.
Just making sure you do understand that.

The transformer plus resistor are meant for a good PM speaker or for a goog FC speaker with FC/VC resistances different from original.