Loud Continuous Thumping Noise Through Car Amp October 25, 2022 Post a Comment Well, the great day has arrived and installed my old BMW Bavaria C Electronic. It was on the shelf for some years and when It was removed it worked brilliantly. Ignition on, antenna goes up, music plays along. All seems ok. Tried AM, FM, cassette. Then suddenly, after a minute playing with the new toy, a loud thumping sound would come on the speakers. Thump thump thump every 0,5 secs aprox. Does it on AM, FM and cassette. Turn it off, then turn it on again. LCD backlight is on but no text on it. After 5 seconds LCD starts working. Strange as it didn't did this on the first attempt. Thumps are there from the start, they do not change with volume. Tried the automatic FM search and it started to work funny, you could see the numbers, sometimes fast, sometimes slow. Now it didn't find any station. Bets on the problem? Good old junk... Thank you! Please register to disable this ad. could it have got damp ? is the power supply to it ok ? how long has it been stood for ? It has been stored like 6 years. It was on a dry storage. Because of the good start it had and then the jerkiness of the lcd when powering up I thought on the 4x1000uF 16V capacitors from the power supply, but the thumping is what makes me wonder. is it getting proper voltage to it ? like 13 14v ish ? sKiZo Hates received: 92644 Check the speaker connections ... could be a wire whisker or something similar, or just a dirty connection causing feedback. I wouldn't run it much as you can destroy an amp like that. I'd pull the radio and hook up to a 12v supply and a set of known good speakers. If you still get thumping, then you've got a bad amp. Please register to disable this ad. It's getting 12.5V. When replaced the radio with the one I'm actually using, the speakers worked as expected. Should this take the speakers out of the equation? sKiZo Hates received: 92644 I'd say that points you more toward having a bad amp. I'd still take a REAL close look at the connector and radio harness. Cracked insulation, bad repair, broken finger, that sort of thing. Something else to check ... any mods to the harness when going with the other radio that works? Might be the old floating ground bugaboo coming back to haunt ya. The loudspeakers have separated grounds. I used a ISO to DIN adapter to connect this radio, but it simply changes the connectors, the wiring is untouched. Floating ground is when the speakers have the same ground? floating speaker ground means speakers have their own grounds not connected to chassis ground . old car radios had same speaker ground as chassis . modern stereos have floating grounds . Please register to disable this ad. Ok, my car speaker installation has a floating ground as so as my current stereo. The old one I'm having the problem with has floating ground too. There were adapters for this radio to connect it to a common ground speaker installation, which obviously I'm not using Maybe you should be looking at the capacitors. Certain brands don't age too well. I fixed a couple of Bose self powered car speakers a few years back which only whined when powered up. Every electrolytic needed replacing (can't remember the brands) and then they worked perfectly thereafter. I believe that the speakers were only 10 years old at the time of repair. Might not be your problem but capacitors are so cheap today, it wouldn't hurt! That's called motorboating, and it's low frequency oscillation. I'd guess filter capacitors, and it probably wouldn't hurt to replace them anyway given their age and the harsh environment they run in. I opened it and it has on the big side 4x1000uF 16V, 4x220uF 16V and 1x3300uF 16V. They are all from the brand FRAKO.I searched on the net and although they were high quality HiFi at the time, people say that they don't stand well the years... And this unit is a Becker from around 1985... Will replace this ones as they are the power and amp ones and see if it makes a difference. Please register to disable this ad. Before you start replacing parts, verify your installation. Motorboating is usually indicative of a low voltage condition. While everybody rushes to check the positive wire for +12v, the ground side gets ignored. Perform a voltage drop test on the ground side of the circuit. a corroded fuse/holder will drop voltage too . Well, replaced all the condensers mentioned above. Plugged it in, the backlight went on but no text out sound, and after a few seconds it started working (I suppose this was the new condensers charging up). Sounds great, it has a warm and deep sound. No more thumping! Power enough to drive my speakers. The only thing I am not happy about is that the system has retractable potentiometers for fader, bass and treble. Fader and treble works good, but bass seems to do nothing. Will check the traces from the pot to the IC and that the pot works. Could this be related to new condensers? They are the same voltage and capacity of the old ones. Any ideas will be appreciated. Thank you for your help and ideas Unlikely. It's more likely a mechanical problem with the bass pot. Please register to disable this ad. Tested the pot with a multimeter. Between the two outer legs I can measure the total resistance. But between the center pin and any of the sides I get an open circuit, regardless of the pot position. Sounds like the finger is shot out it has some kind of debris between the finder and the track. Only thinking on replacing this makes me the day Before you replace, try soft compressed air and some DeOit or other good contact cleaner/lube. Make sure it's a plastic safe product... May try that. I could expect a worn volume pot as you use it continuously to adjust volume or shut off the radio. But a bass pot, I'm sure that almost everyone sets up the bass once or twice. And the thing is that it doesn't have weird values or dead spots. Just out of range on every position of the multimeter and pot (all this measures with the pot on the circuit of course). I reflowed the solder points with no success. Will try some electrical cleaner. How to do it? Between the shaft and the casing? Thank you Share This Page hoffmancontery.blogspot.com Source: https://audiokarma.org/forums/index.php?threads%2Fold-car-stereo-constant-thump.712508%2F Share Post a Comment for "Loud Continuous Thumping Noise Through Car Amp"
Well, the great day has arrived and installed my old BMW Bavaria C Electronic. It was on the shelf for some years and when It was removed it worked brilliantly. Ignition on, antenna goes up, music plays along. All seems ok. Tried AM, FM, cassette. Then suddenly, after a minute playing with the new toy, a loud thumping sound would come on the speakers. Thump thump thump every 0,5 secs aprox. Does it on AM, FM and cassette. Turn it off, then turn it on again. LCD backlight is on but no text on it. After 5 seconds LCD starts working. Strange as it didn't did this on the first attempt. Thumps are there from the start, they do not change with volume. Tried the automatic FM search and it started to work funny, you could see the numbers, sometimes fast, sometimes slow. Now it didn't find any station. Bets on the problem? Good old junk... Thank you!
It has been stored like 6 years. It was on a dry storage. Because of the good start it had and then the jerkiness of the lcd when powering up I thought on the 4x1000uF 16V capacitors from the power supply, but the thumping is what makes me wonder.
Check the speaker connections ... could be a wire whisker or something similar, or just a dirty connection causing feedback. I wouldn't run it much as you can destroy an amp like that. I'd pull the radio and hook up to a 12v supply and a set of known good speakers. If you still get thumping, then you've got a bad amp.
It's getting 12.5V. When replaced the radio with the one I'm actually using, the speakers worked as expected. Should this take the speakers out of the equation?
I'd say that points you more toward having a bad amp. I'd still take a REAL close look at the connector and radio harness. Cracked insulation, bad repair, broken finger, that sort of thing. Something else to check ... any mods to the harness when going with the other radio that works? Might be the old floating ground bugaboo coming back to haunt ya.
The loudspeakers have separated grounds. I used a ISO to DIN adapter to connect this radio, but it simply changes the connectors, the wiring is untouched. Floating ground is when the speakers have the same ground?
floating speaker ground means speakers have their own grounds not connected to chassis ground . old car radios had same speaker ground as chassis . modern stereos have floating grounds .
Ok, my car speaker installation has a floating ground as so as my current stereo. The old one I'm having the problem with has floating ground too. There were adapters for this radio to connect it to a common ground speaker installation, which obviously I'm not using
Maybe you should be looking at the capacitors. Certain brands don't age too well. I fixed a couple of Bose self powered car speakers a few years back which only whined when powered up. Every electrolytic needed replacing (can't remember the brands) and then they worked perfectly thereafter. I believe that the speakers were only 10 years old at the time of repair. Might not be your problem but capacitors are so cheap today, it wouldn't hurt!
That's called motorboating, and it's low frequency oscillation. I'd guess filter capacitors, and it probably wouldn't hurt to replace them anyway given their age and the harsh environment they run in.
I opened it and it has on the big side 4x1000uF 16V, 4x220uF 16V and 1x3300uF 16V. They are all from the brand FRAKO.I searched on the net and although they were high quality HiFi at the time, people say that they don't stand well the years... And this unit is a Becker from around 1985... Will replace this ones as they are the power and amp ones and see if it makes a difference.
Before you start replacing parts, verify your installation. Motorboating is usually indicative of a low voltage condition. While everybody rushes to check the positive wire for +12v, the ground side gets ignored. Perform a voltage drop test on the ground side of the circuit.
Well, replaced all the condensers mentioned above. Plugged it in, the backlight went on but no text out sound, and after a few seconds it started working (I suppose this was the new condensers charging up). Sounds great, it has a warm and deep sound. No more thumping! Power enough to drive my speakers. The only thing I am not happy about is that the system has retractable potentiometers for fader, bass and treble. Fader and treble works good, but bass seems to do nothing. Will check the traces from the pot to the IC and that the pot works. Could this be related to new condensers? They are the same voltage and capacity of the old ones. Any ideas will be appreciated. Thank you for your help and ideas
Tested the pot with a multimeter. Between the two outer legs I can measure the total resistance. But between the center pin and any of the sides I get an open circuit, regardless of the pot position. Sounds like the finger is shot out it has some kind of debris between the finder and the track. Only thinking on replacing this makes me the day
Before you replace, try soft compressed air and some DeOit or other good contact cleaner/lube. Make sure it's a plastic safe product...
May try that. I could expect a worn volume pot as you use it continuously to adjust volume or shut off the radio. But a bass pot, I'm sure that almost everyone sets up the bass once or twice. And the thing is that it doesn't have weird values or dead spots. Just out of range on every position of the multimeter and pot (all this measures with the pot on the circuit of course). I reflowed the solder points with no success. Will try some electrical cleaner. How to do it? Between the shaft and the casing? Thank you
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