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Hallicrafters S120 no speaker output

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Hallicrafters S120 no speaker output Empty Hallicrafters S120 no speaker output

Post by Aaronaaudio on Wed Dec 04, 2019 10:27 am

I'll be getting this thing in the mail here in a few days, price was too reasonable for me to pass up. Previous owner was having no issues with tuning on all bands. Pilots works and the only advertised problem is that he isn't getting anything out of the speaker. Phone jack works great and he was using it with an external speaker.

After taking a peek at the schematic it appears that the speaker and headphone signal come off the same secondary winding in the audio output transformer.

This leads me to think that one, my audio output transformer is ok. Two, the problem is either the speaker itself or the muting switch in the headphone jack. Sound like I'm on the right track?

Probably shouldn't have posted until I receive the damn thing and decide how far I'm going to take it, I'm just trying to work out how this project is going to go down. Probably going to document the refurbishment here, Gonna be fun!


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Post by Tony V on Wed Dec 04, 2019 1:30 pm

It sounds like your on the right track and it should be a simple fix. Keep us posted when you receive the radio. That's a really nice unit and you should get many hours of enjoyment out of it. Good luck!
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Post by Chas on Fri Dec 06, 2019 5:27 pm

Broken flex wire to the voice coil of the speaker or a bad voice coil.

Easy fix for the wire but if it is the voice coil either a new speaker or a recone by a pro $$.

GL

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Post by Aaronaaudio on Sat Dec 07, 2019 12:07 am

Radio arrived today, pulled her apart and everything looks great. I doubt any work has been done previously. All original hallicrafters tubes.

I think you are right chas. Muting switch is good and I believe I have voltage on the speaker. Won't know until I pull my meter out tomorrow and get into it..

Horrible 60hz humm. Found 3 out of the four electrolytics I need in my stash. And pulled a correctly sized speaker out of an old GE solid state.

Pictures and updates to follow...


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Post by Resistance is Futile on Tue Dec 10, 2019 5:20 pm

Well if you're getting a horrible hum then you must be getting that sound through the Speaker, Right?
If this is so then the speaker is OK.

A test for the old speaker is a flashlight battery and wire to touch the speaker terminals. If you get a crackling sound then speaker works.
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Post by Aaronaaudio on Tue Dec 10, 2019 10:40 pm

No, hum was through the headphone jack..the speaker voice coil is open, I clipped in a new speaker temporarily and it works great.

As for functionally restoring the radio so far I have separated the speaker and audio output transformer. Waiting on some caps to come in the mail before I go to town.


Another issue is the insulators(mica?) in the headphone jack are disintegrating. Most likely going to bypass it for now until I find a replacement.

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Post by Chas on Wed Dec 11, 2019 6:14 am

Another issue is the insulators(mica?) in the headphone jack are disintegrating. Most likely going to bypass it for now until I find a replacement.
These are "usually" fiber insulators one or both will have an offset to the center to lock it into the oversized mounting hole. The jack will be mono of the closed circuit type. It could also be a plastic body jack. The closed circuit completes an electrical path to energize the speaker when the headphone plug is removed. The "ring" connection to the plug remains common to one of the speaker connections. Because the radio is transformer-less the output audio circuit is not connected to the chassis or case.

There are vendors for the type (frame) speaker that Hallicrafters used. More modern speakers may not fit properly.

GL

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