jerrytr5 Posted March 26 Report Share Posted March 26 The radio/cd in my 7 has had an intermittent fault where all the speakers stop working. The power to the unit is fine. It's got 4 speakers all separately wired so after checking all the connectors multiple times I came to the conclusion the radio must have an internal fault so swapped it out. But the same fault returned. After more checking, I found that one of the speakers wasn't working properly & disconnecting it appeared to make the fault go away. So, (a) is it possible for a fault in one speaker to cause all the channels to go off? (b) how do you test a speaker? Jerry Quote Link to post Share on other sites
RogerH Posted March 26 Report Share Posted March 26 (edited) Hi Jerry, Without seeing the circuit a little guess work would suggest that if the amplifier section is a big(ish) IC then with one channel having problems the internal safety system may shut it down (on all channels). So the answer is Yes. Replace the speaker Roger Edited March 26 by RogerH Typo Quote Link to post Share on other sites
Charlie D Posted March 26 Report Share Posted March 26 1 hour ago, jerrytr5 said: (b) how do you test a speaker? A rough test would be to connect a 1.5v battery across the speaker terminals. (Just a quick on/off with the battery) You should get a "Click". You could also put a resistance meter across the terminals. Check all 4. They should all read the same value. Charlie. Quote Link to post Share on other sites
stuart Posted March 26 Report Share Posted March 26 1 minute ago, Charlie D said: A rough test would be to connect a 1.5v battery across the speaker terminals. (Just a quick on/off with the battery) You should get a "Click". You could also put a resistance meter across the terminals. Check all 4. They should all read the same value. Charlie. Which is usually written on the back of the speaker magnet I.e. 4 ohms or 8ohms Stuart Quote Link to post Share on other sites
Andy Moltu Posted March 27 Report Share Posted March 27 Could you have an intermittent short on one of the speaker wires. Totally confused the CD/Radio until I found it. Quote Link to post Share on other sites
jerrytr5 Posted March 29 Author Report Share Posted March 29 Checked the wires for shorts, all fine. One of the rear pair of speakers is 3.7 Ohms, the other 0 Ohms so definitely duff. I've had loads of old bangers with a duff speaker, I'm just so surprised that one channel can cut the entire amplifier. Learn something everyday. On the plus side the new head unit has bluetooth and in-built mic so the TR instantly has mobile phone connectivity. Can anyone use a Blaupunkt Atlanta radio/CD player that probably has nothing wrong with it? Jerry Quote Link to post Share on other sites
RogerH Posted March 30 Report Share Posted March 30 Hi Jerry, with 0 (zero) Ohms on one channel the amplifier chip (I assume that is what is in there) is going crazy. It would probably warm up some what and then shut down. If you removed that dead speaker completely the radio may bounce back into life Roger Quote Link to post Share on other sites
Andy Moltu Posted March 30 Report Share Posted March 30 Zero ohms indicates a short, presumably the shutdown is a protective measure. Quote Link to post Share on other sites
RobH Posted March 30 Report Share Posted March 30 3 minutes ago, Andy Moltu said: Zero ohms indicates a short, presumably the shutdown is a protective measure. As Roger says, it is fairly common for more modern car radios to incorporate a shut-down circuit to prevent damage to the output transistors from short circuits. Back in the 1970s they generally didn't, so most radio repair shops kept a good stock of OC28 or 2N3055 transistors depending on the age of the radio........ Quote Link to post Share on other sites
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