I built a dac and took it to a friend's place, but we're unable to connect it out of fear because whenever im holding the rca out from pc (xmos card spdif out) and touch the ground of the rca input of the dac, i get a huge shock, even without the dac turned on. Here are other symptoms
-adjacent electronic (pre) also charges up on the chassis which goes away if i unplug the ac from dac
-i had mains earth connected to dac ground by back to back diode but what this made it happen was the dac would turn on even without the power switch off!
-when the above symptom was happening the transformer in the dac would also vibrate loudly giving off heat
-im unable to use multimeter since i didnt bring one. I thought it would work fine. Everything was ok at home!
-adjacent electronic (pre) also charges up on the chassis which goes away if i unplug the ac from dac
-i had mains earth connected to dac ground by back to back diode but what this made it happen was the dac would turn on even without the power switch off!
-when the above symptom was happening the transformer in the dac would also vibrate loudly giving off heat
-im unable to use multimeter since i didnt bring one. I thought it would work fine. Everything was ok at home!
This situation is extremely dangerous. Consult a skilled local person immediately.
safety earth troubles
i built a tube out dac but the problem has been isolated to the tube section so i'd like to post my question here. no doubt my shoddy construction is to blame but here it is, minus the embarrassing photo- it's this pcb http://www.diyaudio.com/forums/analog-line-level/162125-tube-ss-preamp-3.html#post4351606
in an wooden enclosure with separate transformers for 6v and 110v.
transformers do not have center taps.
when i connect pcb ground via back to back diode to safety earth, the whole circuit turns on! and the transformers vibrate loudly, overheating.
and i get 60v dc on the output terminal grounds when i use ground from other electronics as reference.
the 60v dc goes much higher if the preamp is turned off.
this doesn't happen at my place, only at my friends'.
i'd like to know what the problem is, and how i can remedy it without a metal chassis. i'm ready to swap out transformers. the ones i used for now were very cheap.
i built a tube out dac but the problem has been isolated to the tube section so i'd like to post my question here. no doubt my shoddy construction is to blame but here it is, minus the embarrassing photo- it's this pcb http://www.diyaudio.com/forums/analog-line-level/162125-tube-ss-preamp-3.html#post4351606
in an wooden enclosure with separate transformers for 6v and 110v.
transformers do not have center taps.
when i connect pcb ground via back to back diode to safety earth, the whole circuit turns on! and the transformers vibrate loudly, overheating.
and i get 60v dc on the output terminal grounds when i use ground from other electronics as reference.
the 60v dc goes much higher if the preamp is turned off.
this doesn't happen at my place, only at my friends'.
i'd like to know what the problem is, and how i can remedy it without a metal chassis. i'm ready to swap out transformers. the ones i used for now were very cheap.
mckaym, have you found what the issue is?
earth is correctly wired at the friend's place. finally got a tester and that was the first thing i tested out along with dc on mains.
the dac has a tube output, btw, and i isolated the problem to 220v input 110v output transformer, so yeah, my problem is very similar to mckay's
the transformer has no center tap, and since it's a wooden chassis, nothing else to connect to safety earth. it's an ei transformer and i tried connecting the metal housing to the earth without much difference.
the voltage i get on the rca ground of the dac is 60 something volt in reference to the ground of other electronics. its much higher if the dac is turned off. (???!!)
the issue goes away if i disconnect the 110v transformer but of course also with no sound...
earth is correctly wired at the friend's place. finally got a tester and that was the first thing i tested out along with dc on mains.
the dac has a tube output, btw, and i isolated the problem to 220v input 110v output transformer, so yeah, my problem is very similar to mckay's
the transformer has no center tap, and since it's a wooden chassis, nothing else to connect to safety earth. it's an ei transformer and i tried connecting the metal housing to the earth without much difference.
the voltage i get on the rca ground of the dac is 60 something volt in reference to the ground of other electronics. its much higher if the dac is turned off. (???!!)
the issue goes away if i disconnect the 110v transformer but of course also with no sound...
This could be anything from a lethal problem to a non existent issue.
BUT YOU NEED TO BE SURE WHICH.
A shock from 220 vac caused by faulty equipment would leave no doubt something was seriously amiss. You would be on your back on the floor, not typing about it here and wondering.
If you are not confident on how to test this THEN GET IT CHECKED PROFESSIONALLY.
Connecting a 1500 ohm between the two suspect points (and if it goes up in smoke you have your answer anyway) would allow you to measure any AC voltage developed across that resistor and so calculate current.
Anything over around 0.2milliamps needs investigating.
BUT YOU NEED TO BE SURE WHICH.
A shock from 220 vac caused by faulty equipment would leave no doubt something was seriously amiss. You would be on your back on the floor, not typing about it here and wondering.
If you are not confident on how to test this THEN GET IT CHECKED PROFESSIONALLY.
Connecting a 1500 ohm between the two suspect points (and if it goes up in smoke you have your answer anyway) would allow you to measure any AC voltage developed across that resistor and so calculate current.
Anything over around 0.2milliamps needs investigating.
mckay's situation is most likely this.
https://www.youtube.com/watch?v=l512uWJ0mgQ
However this kind of things does not cause the transformer to scream in agony like in donovas's case. Any situation that results in heat and noise(!) needs to be taken very seriously.
https://www.youtube.com/watch?v=l512uWJ0mgQ
However this kind of things does not cause the transformer to scream in agony like in donovas's case. Any situation that results in heat and noise(!) needs to be taken very seriously.
Hard to say. You would need to look at all possible causes.
If the Pioneer has a two core lead (is that as originally designed and approved ?) then perhaps some leakage or coupling from the transformer is occurring. Wouldn't like to guess on that tbh although it should be possible to find the cause with methodical testing.
If the Pioneer has a two core lead (is that as originally designed and approved ?) then perhaps some leakage or coupling from the transformer is occurring. Wouldn't like to guess on that tbh although it should be possible to find the cause with methodical testing.
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