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Rca ground shocks
Rca ground shocks
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Old 26th January 2017, 11:56 AM   #21
mckaymckaymckay is offline mckaymckaymckay  United Kingdom
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Yes its probably that wwemze.

Its happened on varied equipment over the years and i thought it was some kind of earthing mismatch as its always when you put yourself between earth points.

PC's and CRT monitors used to do it quite abit.
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Old 26th January 2017, 12:17 PM   #22
donovas is offline donovas  South Korea
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i'd like to bandage the problem instead of rebuilding the whole thing since this is more of a learning project for me.

im thinking of getting a better transformer for 110v duty. should i go for center tapped on the secondary so that i can earth the center?
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Old 26th January 2017, 02:26 PM   #23
donovas is offline donovas  South Korea
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To get more help from different people?

No i dont have autoformer.
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Old 26th January 2017, 03:17 PM   #24
DF96 is offline DF96  England
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Quote:
Originally Posted by donovas
should i go for center tapped on the secondary so that i can earth the center?
Does the circuit require a secondary CT? If so, you need to provide it. If not, you do not need to provide a CT and if one is present you should ignore it and certainly should not ground it. You seem to be fumbling in the dark here. Do you understand power supplies? Who built the one with the faults in it?
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Old 26th January 2017, 04:24 PM   #25
kevinkr is offline kevinkr  United States
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Rca ground shocks
Multiple threads on the same topic are a violation of forum rules. Please read the rules. Threads have been merged.
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Old 27th January 2017, 04:30 AM   #26
donovas is offline donovas  South Korea
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thank you~

so this is the circuit im going by

http://www.diyaudio.com/forums/attac...chematics1.jpg

like i said, the whole machine turns on when i connect the signal ground to earth via back to back resistor.

but as you can see on the circuit, the output is shorted to ground when the relay is not active. could it be the shock im getting is from residual charge in the smoothing cap after the regulator? and the residual charge is unable to drain because i dont have the earth connected.

Last edited by donovas; 27th January 2017 at 04:34 AM.
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Old 27th January 2017, 04:36 AM   #27
jean-paul is offline jean-paul  Netherlands
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Quote:
Originally Posted by donovas View Post
but as you can see on the circuit, the output is shorted to ground when the relay is not active. could it be the shock im getting is from residual charge in the smoothing cap after the regulator? and the residual charge is unable to drain because i dont have the earth connected.
Oh oh that is not wise ! This is a device that must have its case tied to PE. It has a metal chassis probably (I see you have a wooden case but still there will be metal parts) and lethal voltages anyway so all exposed metal parts must be connected to PE certainly when it is a DIY device. With tube gear it is wise to reference audio GND to PE. The back to back diode system works. It wonders me what there is different in your friends house. I think he has a problem with his electrical system. This way of working without PE is very dangerous. Even in normal state you get shocks, now suppose what happens if a real failure occurs.

Quote:
Originally Posted by donovas View Post
-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 indicates a serious issue in the home of your friend. It seems that PE has a voltage on it in his home. It can be a combination of a failure in your DAC and a failure in the electrical system but in all cases you will have to have a certified electrician look into it. This can be a very dangerous situation for your friend and his family. First have his installation checked and don't use the DAC for now until you know what is wrong in the house of your friend. If that is solved pay then attention to making the DAC PE connected.
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Last edited by jean-paul; 27th January 2017 at 04:53 AM.
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Old 27th January 2017, 06:40 AM   #28
donovas is offline donovas  South Korea
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My guess is that earth is floated in my friend's place, and creates an ac loop, effectively making it another ac polarity when i connect the ground wire to it. At my place there is no separate earth wiring (a lot of old places in korea are like that) and instead one ac polarity has more ground potential (i think) so the current is able to drain out into that.


What i plan on doing is

-get a new 110v transformer wound with earth tab (its an ei transformer)
-get a metal plate to mount all the transformers on and earth the plate
-maybe get the 110v transformer center tapped and earth it too?

Hopefully these will do the trick. What do you think?
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Old 27th January 2017, 07:40 AM   #29
john_tracy is offline john_tracy  United States
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Quote:
At my place there is no separate earth wiring
This opens the possibility that the unit itself is wired incorrectly and works at your house because there is no mains ground connection. When plugged in at your friend's house with a ground connection the issue appears.
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Old 27th January 2017, 08:23 AM   #30
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by jean-paul View Post
..................... all exposed metal parts must be connected to PE certainly when it is a DIY device. .................
At last.
You are finally stating that the the second rule applying to exposed conductive parts does apply!

Why in so many other posts do you insist that we should not be making this Safety connection?
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