J
jackdoor
Hello, Having been called out to a multi audio channel set up (surround sound)with a faulty subwoofer with hum on it ,confirmed by removing the sub from rest of system,
On repairing the sub, DC decoupling fault,and testing ok, returned the unit to customer,installing to system,on checking the hum was still there.
Removing the cable removed the hum.Checked the sub with another cable ..same fault.
The sub was connected to an AV amplifier.5.1 surround.
Removing all the input Phonos and coaxial digital cables cured the fault .
connecting individually .the tivo box was the cause of the hum, removing the 2 hdmi leads from TV cured the fault,in fact individually pluging them in no problem.the only other connection were the digital coaxial and virgin's transmission cable.Removing this cabel cured the fault.
An earth loop? dont see how, as all connected appliances are double isolated with no earth
The tivo box has a digital coaxial, grounded to chassis,think other virgin boxes and sky have optical outs.
Have seen forums where connect coaxial virgin cable to earth pin in plug.Tried this but reduced hum by 50% not a cure.
On trying to speek to virgin,they dont want to know, as third party equipment,The customer had virgin down for another problem with phone and asked the engineer ,with the same response.and advised to disconnect the earth as may cause problems with their cable transmission units.
Suggesed to customer to use earth isolator in cable inlet cable .
Would this cause a problem with reception isolating the screen from virgin?
The problem seems to stem from the tivo box not having a optical digital output which is isolated from the chassis.
The other option is to use a digital coaxial phono to a optical adapter to isolate the earth,hav'nt tried yet one on order and isolator.
Would this problem relate to any one out there, has anyone had this problem before ,seems to be lots of problems relating to this fault ,as being a TV engineer would like a different view. Thanks Vince.
On repairing the sub, DC decoupling fault,and testing ok, returned the unit to customer,installing to system,on checking the hum was still there.
Removing the cable removed the hum.Checked the sub with another cable ..same fault.
The sub was connected to an AV amplifier.5.1 surround.
Removing all the input Phonos and coaxial digital cables cured the fault .
connecting individually .the tivo box was the cause of the hum, removing the 2 hdmi leads from TV cured the fault,in fact individually pluging them in no problem.the only other connection were the digital coaxial and virgin's transmission cable.Removing this cabel cured the fault.
An earth loop? dont see how, as all connected appliances are double isolated with no earth
The tivo box has a digital coaxial, grounded to chassis,think other virgin boxes and sky have optical outs.
Have seen forums where connect coaxial virgin cable to earth pin in plug.Tried this but reduced hum by 50% not a cure.
On trying to speek to virgin,they dont want to know, as third party equipment,The customer had virgin down for another problem with phone and asked the engineer ,with the same response.and advised to disconnect the earth as may cause problems with their cable transmission units.
Suggesed to customer to use earth isolator in cable inlet cable .
Would this cause a problem with reception isolating the screen from virgin?
The problem seems to stem from the tivo box not having a optical digital output which is isolated from the chassis.
The other option is to use a digital coaxial phono to a optical adapter to isolate the earth,hav'nt tried yet one on order and isolator.
Would this problem relate to any one out there, has anyone had this problem before ,seems to be lots of problems relating to this fault ,as being a TV engineer would like a different view. Thanks Vince.
