thebes Posted March 6, 2012 Share Posted March 6, 2012 Playing aorund with an old GE Musaphonic tube radio. I've swapped out a couple of caps and rebuilt the power supply, lubed etc. It's much quieter now, but the twin pair of 6" speakers are not much to write home about. I'd like to swap out the speakers. They are not labelled for impedance so hence my question. Also, could I drop in some automobile speakers for these, since they are cheap and can sound kinda good? This thing actually has a turntable circuit besides AM and FM so it might make a good casual listening box in my work room. Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted March 6, 2012 Share Posted March 6, 2012 Marty, do you have the model number? If not, tell me what the audio output tube(s) are and I can help you out-- Maynard Quote Link to comment Share on other sites More sharing options...
Don Richard Posted March 6, 2012 Share Posted March 6, 2012 Get an ohmmeter then measure the resistance of one of the drivers. If the DCR is 3 point something you have a 4 ohm nominal impedance. 6 ohms or so would be 8 ohms nominal impedance, and 10-12 ohms or more would be 16 ohms nominal impedance. Should be close enough for government work. Most autosound speakers run about 4 ohms and series connecting them for 8 ohms could yield wierd results if they use blocking caps as a crossover of sorts. YMMV Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted March 6, 2012 Share Posted March 6, 2012 Marty, if that's an AC/DC radio there are some very definite electrical safety concerns which you should be aware of (especially if you're going to do an kind of testing or measuring while it's powered up.) Feel free to email if you want me to explain the concerns and how to address them. Quote Link to comment Share on other sites More sharing options...
thebes Posted March 7, 2012 Author Share Posted March 7, 2012 Thanks guys and sorry to be just replying. Mike Lindsey and I were at the Jimi Hendrix Experience 2012 Tour kickoff last night. The model is T150B. Here's a link: http://www.radiomuseum.org/r/general_el_t150bt_150_musaphoni.html Unfortunately, I'm not a member so I can't access the schematic. It's for sure AC to DC using a 35G6L6as a rectifier, and I presume 12Au6's for power. This is my first foray into tube radios, and I'm confused as to how they get to the output without using output transformers. Don, are you talking about taking the measurements with it powered up, because, powered down, I'm getting about .3 ohms. Maynard, whatever help you have to offer is greatly appreciated, unless, of course, you urge me to install high-end cables.[] Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted March 8, 2012 Share Posted March 8, 2012 Hi Marty- I'll have the schematic some time this afternoon. Will be in touch after I take a look at it. It's a bit too "new" for my database, but one of my radio buddies has it!!! Quote Link to comment Share on other sites More sharing options...
Don Richard Posted March 8, 2012 Share Posted March 8, 2012 Any ohmmeter measurements should be made with the speaker disconnected from the radio. Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted March 8, 2012 Share Posted March 8, 2012 Hi Marty- Email sent. Will chat with you later on. Maynard Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.