"actually if i really wanted to be sure i would short the signal and ground on RCA inputs, not just disconnect the cable."
Thats non sense and waste of time, turning the Volume control al the way down on the sub amp will do.
Your persisting problem most be ground loop , caused by the use of the non proprietary cable. Not impossible to fix though.
Thats non sense and waste of time, turning the Volume control al the way down on the sub amp will do.
Your persisting problem most be ground loop , caused by the use of the non proprietary cable. Not impossible to fix though.
The rectifier has been removed, I have tested it with an analog multimeter and found the following:
Rectifier: - ~ ~ +
Meter:...........- + reads 9 ohms at x1k
Rectifier: - ~ ~ +
Meter:.......-.....+ reads 8 ohms at x1k
Rectifier: - ~ ~ +
Meter:....-........+ reads 22 ohms at x1k
Rectifier: - ~ ~ +
Meter:....-.....+ reads 8 ohms
Rectifier: - ~ ~ +
Meter:....-..+ reads 8 ohms
all other combinations show no continuity.
I read the link you gave to ...allaboutcircuits... and I didn't quite get it, then I searched around and found this page,
http://www.kpsec.freeuk.com/components/diode.htm#bridge
and the animated picture helped me understand a bit better, although I am still fascinated that it shows open circuit one way and short the other.
I still don't know enough to tell if what I found means it is good or faulty.
Thanks so much for the help with this. I don't know if we will be successful in repairing this, but I have learned a lot so far, and have also developed my soldering and de-soldering skills!
Rectifier: - ~ ~ +
Meter:...........- + reads 9 ohms at x1k
Rectifier: - ~ ~ +
Meter:.......-.....+ reads 8 ohms at x1k
Rectifier: - ~ ~ +
Meter:....-........+ reads 22 ohms at x1k
Rectifier: - ~ ~ +
Meter:....-.....+ reads 8 ohms
Rectifier: - ~ ~ +
Meter:....-..+ reads 8 ohms
all other combinations show no continuity.
I read the link you gave to ...allaboutcircuits... and I didn't quite get it, then I searched around and found this page,
http://www.kpsec.freeuk.com/components/diode.htm#bridge
and the animated picture helped me understand a bit better, although I am still fascinated that it shows open circuit one way and short the other.
I still don't know enough to tell if what I found means it is good or faulty.
Thanks so much for the help with this. I don't know if we will be successful in repairing this, but I have learned a lot so far, and have also developed my soldering and de-soldering skills!
I almost forgot, the rectifier is a PBU1001, and the spec sheet can be found at:
http://www.ortodoxism.ro/datasheets/diodes/ds21309.pdf
http://www.ortodoxism.ro/datasheets/diodes/ds21309.pdf
Hi,
the reverse direction will show as near open circuit on the ohms scale.
The forward direction can show open circuit or a false resistance depending on the voltage applied during the measurement.
If the test voltage is >700mV then current flows and a resistance is indicated. If <500mV then no current flows and open circuit will be indicated. Some meters have a dual test voltage switch to allow this test to be done at <diode voltage. This dual facility is also useful for checking transistors and assembled PCBs.
Your 22r reading indicates that your meter is applying a test voltage >1.5V when on ohms scale.
I think the open circuit readings show that your rectifiers are OK.
the reverse direction will show as near open circuit on the ohms scale.
The forward direction can show open circuit or a false resistance depending on the voltage applied during the measurement.
If the test voltage is >700mV then current flows and a resistance is indicated. If <500mV then no current flows and open circuit will be indicated. Some meters have a dual test voltage switch to allow this test to be done at <diode voltage. This dual facility is also useful for checking transistors and assembled PCBs.
Your 22r reading indicates that your meter is applying a test voltage >1.5V when on ohms scale.
I think the open circuit readings show that your rectifiers are OK.
Hi, Yes I agree looks like the rectifier is OK. I am now running out of ideas.
The bridge animation is good and I can see how it would help.
So to recap.
It didn't hum out of the box.
In the box it hums a bit.
When you connect a source it hums much worse.
If you disconect the source again the hum does not go away.
I guess to be sure we should eliminate the ground loop issue.
Take a peice of wire and short the input to the unit ie from the outside of the RCA connector to the inside of the RCA connector. Does the hum go away. (It is safe to short the input as it effectively puts nothing on the input - do not short the output it could damage the unit)
I don't know this product:- If it has a volume control, does the volume control affect the level of the hum?
Regards,
Andrew
The bridge animation is good and I can see how it would help.
So to recap.
It didn't hum out of the box.
In the box it hums a bit.
When you connect a source it hums much worse.
If you disconect the source again the hum does not go away.
I guess to be sure we should eliminate the ground loop issue.
Take a peice of wire and short the input to the unit ie from the outside of the RCA connector to the inside of the RCA connector. Does the hum go away. (It is safe to short the input as it effectively puts nothing on the input - do not short the output it could damage the unit)
I don't know this product:- If it has a volume control, does the volume control affect the level of the hum?
Regards,
Andrew
Here is a link with some more details about the system:
http://support.gateway.com/s/SOUND/speakers/7002204/7002204nv.shtml
There were a couple of revisions, and not exactly sure which one I have, but the main difference is some have a digital input in addition to the analog input, which mine has. I am using the analog (mini stereo plug) input.
I put the rectifier back in, and re-did the soldering on the large cap I installed earlier, as I wanted to make sure that was making good connection. I then attached the 2 speakers (the volume control is on one of the speakers). There is also a control cable from the speaker with the volume, surround mode, and subwoofer controls. I attached it, turned on the volume, and there was a hum, but quieter than before. I then plugged in the source, played something thru the computer, and it sounded pretty good. With music playing I can't hear the hum.
I then turned it off, attached the sub speaker, turned it back on, and the sub hummed very loudly. None of the humming is affected by the volume control. It starts humming when it is turned on now, and seems to always hum. Attaching/removing the source doesn't affect it.
There are 3 other caps, each 25v, 220uf, and one other 10v, 220uf on the boards.
I tried checking the input for ground loop, and since it is a stereo plug, I shorted all the combinations of the 3 wires and it didn't affect anything.
So now I have barely noticeable humming on the satellite speakers, and loud humming on the sub speaker when it is connected. The sub noise is at least as loud as it was before I started working on it.
http://support.gateway.com/s/SOUND/speakers/7002204/7002204nv.shtml
There were a couple of revisions, and not exactly sure which one I have, but the main difference is some have a digital input in addition to the analog input, which mine has. I am using the analog (mini stereo plug) input.
I put the rectifier back in, and re-did the soldering on the large cap I installed earlier, as I wanted to make sure that was making good connection. I then attached the 2 speakers (the volume control is on one of the speakers). There is also a control cable from the speaker with the volume, surround mode, and subwoofer controls. I attached it, turned on the volume, and there was a hum, but quieter than before. I then plugged in the source, played something thru the computer, and it sounded pretty good. With music playing I can't hear the hum.
I then turned it off, attached the sub speaker, turned it back on, and the sub hummed very loudly. None of the humming is affected by the volume control. It starts humming when it is turned on now, and seems to always hum. Attaching/removing the source doesn't affect it.
There are 3 other caps, each 25v, 220uf, and one other 10v, 220uf on the boards.
I tried checking the input for ground loop, and since it is a stereo plug, I shorted all the combinations of the 3 wires and it didn't affect anything.
So now I have barely noticeable humming on the satellite speakers, and loud humming on the sub speaker when it is connected. The sub noise is at least as loud as it was before I started working on it.
Hi,
As its not affected by the grounding or volume control. It still sounds like there is a problem with the PSU.
Possibilities - the bridge works off load and fails as soon as any power is draw through it (I have seen this before)
There is another bridge somewhere and this has failed. I don't think this is likely as I suspect there is only one rail comming from the PSU.
I suggest measuring the AC and the DC voltage on each of the caps including the one you replaced. I.e test it with the meter in AC then in DC. The AC should be low and the DC high.
Let us know what this is and it should help to work out where to go from here.
Regards,
Andrew
As its not affected by the grounding or volume control. It still sounds like there is a problem with the PSU.
Possibilities - the bridge works off load and fails as soon as any power is draw through it (I have seen this before)
There is another bridge somewhere and this has failed. I don't think this is likely as I suspect there is only one rail comming from the PSU.
I suggest measuring the AC and the DC voltage on each of the caps including the one you replaced. I.e test it with the meter in AC then in DC. The AC should be low and the DC high.
Let us know what this is and it should help to work out where to go from here.
Regards,
Andrew
The 25v, 22000uf cap shows 37v ac, 18v dc
the two 25v, 220uf caps side by side on the same board as the cap above show nothing at all.
Another 25v 220uf cap shows 37v ac, 18v dc.
The last cap, a 10v 220uf cap shows 10v ac, 5v dc.
I checked the power transformer, and it is putting out about 14v ac.
To my untrained eye, I don't recognize another rectifier.
the two 25v, 220uf caps side by side on the same board as the cap above show nothing at all.
Another 25v 220uf cap shows 37v ac, 18v dc.
The last cap, a 10v 220uf cap shows 10v ac, 5v dc.
I checked the power transformer, and it is putting out about 14v ac.
To my untrained eye, I don't recognize another rectifier.
Now I am confused.
Either your meter is showing an erronious measurement or there is something really bad going on.
That cap won't last for long with 37Vac as its only made for 25V.
It would certainly explain the hum. But I don't understand where it can be comming from if the AC supply is only 14V, my guess is that your meter is picking up DC and AC for some reason. What sort of meter do you have?
At this point, I would replace the bridge to see if it fixes the problem, its the only thing I can think of that would cause this level of ripple.
Regards,
Andrew
Either your meter is showing an erronious measurement or there is something really bad going on.
That cap won't last for long with 37Vac as its only made for 25V.
It would certainly explain the hum. But I don't understand where it can be comming from if the AC supply is only 14V, my guess is that your meter is picking up DC and AC for some reason. What sort of meter do you have?
At this point, I would replace the bridge to see if it fixes the problem, its the only thing I can think of that would cause this level of ripple.
Regards,
Andrew
I was using a 20 year old analog meter. I will try a different one tonight and see what the results are.
How does the power go from 14v ac at the power supply to 25 or 37v at the caps? And then only 10v at the small cap?
Also, the power transformer shows the secondary should be 12v, but the meter was reading 14v. (I will check that again with a different meter when I get time.)
Thanks.
How does the power go from 14v ac at the power supply to 25 or 37v at the caps? And then only 10v at the small cap?
Also, the power transformer shows the secondary should be 12v, but the meter was reading 14v. (I will check that again with a different meter when I get time.)
Thanks.
Hi, The 14V read by your meter will be 14V RMS. So you get 14 x 1.41 for the peak value which is 19.74V.
So the AC signal is 19.47 x 2 peak to peak 39.48V.
It is normal for a transformers output to be a bit higher than listed on it when it is off load as it sags on load. Also the mains is often a bit higher than the nominal value and this would push the output of the transformer up as well.
10V on the smaller cap is probably because there is a regulator on the supply to reduce the voltage for these circuits.
Regards,
Andrew
So the AC signal is 19.47 x 2 peak to peak 39.48V.
It is normal for a transformers output to be a bit higher than listed on it when it is off load as it sags on load. Also the mains is often a bit higher than the nominal value and this would push the output of the transformer up as well.
10V on the smaller cap is probably because there is a regulator on the supply to reduce the voltage for these circuits.
Regards,
Andrew
I just tested everything with a digital meter and found slightly different readings than before:
The 25v, 22000uf cap shows 34.1v ac, 16v dc
the two 25v, 220uf caps side by side on the same board as the cap above show .1 or .2v ac and .3v dc on one, and 0.0v ac and .1v dc.
Another 25v 220uf cap shows 34.1v ac, 16v dc.
The last cap, a 10v 220uf cap shows 9.9v ac, 4.9v dc.
What do you think about the two caps that show so little voltage?
I had to do some more study on the rms, peak, etc. So I understand a bit more of the theory, and that my meters do not take true rms readings, but not sure if that means the 34v ac is high or not.
These parts are relatively inexpensive, so I don't mind replacing the bridge and/or caps if you still think that is the way to go.
btw, I checked the voltage on the bridge under load and got 15.9v dc on the outside pins and 13.4v ac on the inside pins.
Thanks.
The 25v, 22000uf cap shows 34.1v ac, 16v dc
the two 25v, 220uf caps side by side on the same board as the cap above show .1 or .2v ac and .3v dc on one, and 0.0v ac and .1v dc.
Another 25v 220uf cap shows 34.1v ac, 16v dc.
The last cap, a 10v 220uf cap shows 9.9v ac, 4.9v dc.
What do you think about the two caps that show so little voltage?
I had to do some more study on the rms, peak, etc. So I understand a bit more of the theory, and that my meters do not take true rms readings, but not sure if that means the 34v ac is high or not.
These parts are relatively inexpensive, so I don't mind replacing the bridge and/or caps if you still think that is the way to go.
btw, I checked the voltage on the bridge under load and got 15.9v dc on the outside pins and 13.4v ac on the inside pins.
Thanks.
Hi,
I don't really know what is going on. But if it was my peice of kit I would replace the bridge at this point. There should not be that much AC on the caps and the only thing I can think of to cause it is a faulty bridge, but I could easly be wrong.
Don't worry about the caps with no voltage on them they may be part of the Audio circuit which would only have voltage across it when there is a signal present and even then it might not be much.
Regards,
Andrew
I don't really know what is going on. But if it was my peice of kit I would replace the bridge at this point. There should not be that much AC on the caps and the only thing I can think of to cause it is a faulty bridge, but I could easly be wrong.
Don't worry about the caps with no voltage on them they may be part of the Audio circuit which would only have voltage across it when there is a signal present and even then it might not be much.
Regards,
Andrew
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