Ge Superadio II - Nothing from tweeter

I have a GE Superadio II that i picked up on Ebay a few years ago for about $20. It works fine and sounds great however no sound ever came from the tweeter. I should mention that I know very little about ohms, resistance etc but I am handy and know how to solder, I see that the silent tweeter is marked 140 ohms. While it is very light and cheap looking I have a 8 ohm tweeter, I salvaged from an otherwise nonfunctioning Altec Lansing computer speaker, which looks and feels substantial. It has heft because it has a magnet. Sorry that's about as technical as I can get. I see that the tweeter is wired from the woofer. There's a blobby looking component that's between the woofer and the + terminal of the tweeter that I assume is some sort of resister. My question is should i remove the silent 140 ohm tweeter and replace it with the 8 ohm tweeter or do I need to find a tweeter that is rated the same as the existing tweeter? Also if I do install the 8 ohm tweeter should I leave the existing resister in place, put something different there or ditch the entire project because something other than the existing tweeter itself may be bad.

da5is said:

I have a GE Superadio II that i picked up on Ebay a few years ago for about $20. It works fine and sounds great however no sound ever came from the tweeter. I should mention that I know very little about ohms, resistance etc but I am handy and know how to solder, I see that the silent tweeter is marked 140 ohms. While it is very light and cheap looking I have a 8 ohm tweeter, I salvaged from an otherwise nonfunctioning Altec Lansing computer speaker, which looks and feels substantial. It has heft because it has a magnet. Sorry that's about as technical as I can get. I see that the tweeter is wired from the woofer. There's a blobby looking component that's between the woofer and the + terminal of the tweeter that I assume is some sort of resister. My question is should i remove the silent 140 ohm tweeter and replace it with the 8 ohm tweeter or do I need to find a tweeter that is rated the same as the existing tweeter? Also if I do install the 8 ohm tweeter should I leave the existing resister in place, put something different there or ditch the entire project because something other than the existing tweeter itself may be bad.

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Beware of your 8 Ohm tweeter - the magnet may be enough to saturate the ferrite bar antenna, reducing AM sensitivity. That blobby component is probably a capacitor, which blocks low frequencies from damaging the tweeter. If you must use the 8 ohm tweeter, I would find a 130 Ohm resistor to put in series with it, so you will match the original impedance.

Thanks so much for the responses. The GE specs for the Superadio II say the tweeter is a 140 ohm Piezo. I read a capacitor is not required because piezo itself is naturally capacitance. In light of that and if indeed the capacitor is what is bad, not the tweeter, could I just remove the capacitor? Here is a photo of the blob component that I mentioned.

Are you 100% sure the tweeter is bad? I have an SRII and you often literally have to cover the tweeter with your hand to tell if it's working a lot of times -- and that's on FM. Not enough treble comes through on AM to kick it in.

Being that there's only 500-700 mw of power produced from the audio in the SRII's chip, it's difficult to think it would fry. The crossover cap still works with my radio, and it's an original part.

boombox4 said:

Are you 100% sure the tweeter is bad? I have an SRII and you often literally have to cover the tweeter with your hand to tell if it's working a lot of times -- and that's on FM. Not enough treble comes through on AM to kick it in.

Being that there's only 500-700 mw of power produced from the audio in the SRII's chip, it's difficult to think it would fry. The crossover cap still works with my radio, and it's an original part.

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What I meant in the last sentence in that post was "it's difficult to think the tweeter would fry." Because not enough power goes through it to fry the tweeter, and unless the capacitor is an electrolytic (I don't remember, and the one in your picture doesn't look like one) it probably wouldn't fail under normal circumstances, even 20+ years later. The electrolytics in my SRII are all fine.

I just pulled out my SRII and it's hard to tell when the tweeter is really engaged. Some FM stations really don't boost the highs like they used to when CD's were a big deal. The advent of the Mp3 / Music On Hard Drive sort of changed that. A bit less of that crystal clear high end that seemed to be more prominent when CD audio was the big deal on FM when these radios came out (station engineers, feel free to correct me if you wish).

Either way, good luck with your SRII. They're great radios.

Maybe you're correct boombox. It's hard to put my ear against the tweeter and discern with the woofer right next to it. The radio sounds great so I should just leave it as is.

A lot of treble does go through the woofer. If you ever heard a Superadio I, the II's predecessor, you'd be able to tell easier.

I'd just resolder the capacitor and trust that the tweeter works.

Good luck, and enjoy your SRII. They're great radios, and tough. Mine took a dive off a refridgerator and didn't even get a scratch. Good DX radio too.

I played with piezos when they arrived on the scene. Motorola had the patent and I got a stash of engineering samples to evaluate with TEF. They had response that /went out to 40kHZ however they were prone to resonate at various frequencies and to my ears were better suited for uses such as waking you up in the morning with an annoying beep.

I still have my original early version Superadio (70s) that works quite well...very sensitive on both bands and really good selectivity.

The piezo tweeters looked like a capacitor load that had a slope down in impedance with rising frequency. Most cheap two-way speakers of the day simply connected the tweeter directly to the woofer with the neg common and a resistor from the the amp-driven woofer plus to tweeter plus. The resistor was to keep the tweeter from looking like a short circuit to the amplifier at high frequencies. A volume control was often the next step up in complexity instead of a fixed resistor so you could adjust the drive to the tweeter.

I prefer a single speaker as you don't get the time alignment problem of a woofer and tweeter not coming from the same acoustic center...I would just leave it disconnected or not working if it was mine.

Here is a company that carried on the Motorola stuff. http://piezosourcestore.bestgrouptechnologies.com/index.php

I would leave the tweeter in & wired stock, as the radio was designed to work with it that way... but that's just me.

My SR3, btw, is the same way as my SR2 -- the tweeter works, but you have to strain your ears to hear it working, even on FM.