Recently I bought an LG External DVD Writer that is TV compatible. But after a couple of times it stopped working on my Sony LED TV. It would start spinning, but stop after two seconds. This would go on and on.

I assumed that it wasn't receiving enough power from the TV USB port (the DVD writer was rated to 1.6A). So I made a simple USB Y-connector where I took two male USB plugs and one female. Connected the red and black of the female to one of the male USB and the green and yellow alone to the second male USB plug.
Y cable Schematic

I connected the data Male USB to my PC and plugged in the power male USB to a USB power adapter rated to 2.1A. Finally I plugged in a USB thumb drive to the female USB plug to test it out.

But there doesn't seem to be any activity.

Is there something wrong with the wiring itself or simply because there is an improper connection made.

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    \$\begingroup\$ That's not a Y-connector. You only supply power from one USB port -- assuming your commodity-cables follow some sort of color code. \$\endgroup\$ – Scott Seidman Feb 22 '16 at 13:28
  • \$\begingroup\$ Well, I assumed that the Drive would draw power from the adapter and provide data to the TV. Wouldn't it work like that ? \$\endgroup\$ – BharathYes Feb 22 '16 at 13:31
  • \$\begingroup\$ A- not unless you tie the grounds together, and B- these Y adapters are generally used when power from one port is not enough. \$\endgroup\$ – Scott Seidman Feb 22 '16 at 13:37
  • \$\begingroup\$ @ScottSeidman I'm wondering if the tv's USB-powering circuit may have been damaged by pushing the 1.6A load previously. I'm gjesskng that many mfgrs probavly design those ports around the 0.1-0.5A loading of the 'dongles' that usually are used there, but don't always change the firmware to not allow negotiation to 'turn up the juice' & potentially damage the power-handling components. \$\endgroup\$ – Robherc KV5ROB Feb 22 '16 at 13:45
  • \$\begingroup\$ I regularly use External Harddisks on the port without any issue. Even the DVD writer worked fine the first time I plugged in. This issue started from the next. I used the DVD writer on my PC in between that . The TV USB ports on working fine till now. \$\endgroup\$ – BharathYes Feb 22 '16 at 13:52

If I understood your question correctly, you left the original plugs black wire completely disconnected from the player. By doing this, you severed the ground connection between the player and TV. If your PC and TV had different ground potentials (they almost certainly have due to wire inductance and power supply filter capacitors), the signal wires were subjected to excessive voltages and currents. It is possible that you killed both the DVD players and TVs USB ports.


If I recall correctly from some USB work I was doing a couple of years ago...

Part of the USB protocol allows USB host devices to detect plug-in events on the USB power wires as a signal to begin link negotiation with a newly attached client device; thus allowing a sort of 'power-save,' or 'ignore' feature on a host with no attached clients.

Based on that, and the VERY IMPORTANT point made in @jms' answer, might I suggest the following modification to your cable:
enter image description here
As a rather basic power-boost 'Y' cable, this should work; but be sure to label the "power only" male connector to save yourself a lot of frustration in the future.

  • \$\begingroup\$ But wouldn't joining the two red connection cause a problem like short the USB port on my TV or something ? \$\endgroup\$ – BharathYes Feb 22 '16 at 13:47
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    \$\begingroup\$ Also while soldering these wires I noticed that there was a fifth wire, mostly in grey or without insulation in the USB cable. Is that of any significance here ? \$\endgroup\$ – BharathYes Feb 22 '16 at 13:49
  • \$\begingroup\$ Assuming both the TV's and charger's grounds are connected, and the charger operated within usb specification, the reds being connected should be no problem. However, if you would feel better by using it, a schottky diode on the red wire from the tv's connector would block any back-feed. Also, keeping the red complete on all 3 ends has the benefit of allowing you to still use the nea cable when you don't need a second power source. \$\endgroup\$ – Robherc KV5ROB Feb 22 '16 at 14:00
  • \$\begingroup\$ @BharathYes That 5th wire is most likely the grounded jacket; in higher-quality cables it exists as a shielding foil/braid, similar to in a coax cable, and protects your data wires from most EMI/RFI interferance. It would be a very good idea to at least keep it connected between the 3 ends, as it is connected to 'chassis ground' on your devices/plugs (it connects to the rectangular metal housing of the plugs & sockets). \$\endgroup\$ – Robherc KV5ROB Feb 22 '16 at 14:02
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    \$\begingroup\$ @RobhercKV5ROB Not really. You'll create a ground loop which will pick up extra noise. \$\endgroup\$ – Dmitry Grigoryev Feb 22 '16 at 14:51

USB signals are not limited to D+ and D- lines (the spec mandates those to be White and Green wires, your cable doesn't seem to fully complain). Detection of a new device, as well as negotiation of protocol version is done by setting specific voltage levels on D+ to ground and D- to ground. So you absolutely need to keep the black wire (hopefully it's the ground, but impossible to tell for sure) between the disk and the TV.

Whenever you want to connect the +5V line to all three terminals is up to you. If you do, USB spec guarantees that voltage on D+ and D- will never rise above that level, causing damage. On the other end, you'll short two +5V regulators together (the one in your TV and your external adapter), which will create parasite currents between them. It's hard to tell which option is best, in fact, USB spec prohibits Y-cables straight away because they can't be implemented properly.

  • \$\begingroup\$ Well. I actually bought two wires from a local store. Y connector with three males and one without h two females. But when I used it, the drive took and awful lot of time just to power up and he eject never worked. That is why I am creating this on my own. \$\endgroup\$ – BharathYes Feb 22 '16 at 15:47
  • \$\begingroup\$ will it work if just the three grounds are connected cos I am sceptic of connecting the power since TV is brand new and I don't want to damage it \$\endgroup\$ – BharathYes Feb 22 '16 at 15:48
  • \$\begingroup\$ The fact that Y connectors are sold doesn't make them compliant. And yes, you can try to connect Green+Yellow+Black to your TV and Red+Black to the external adapter, and it should work. \$\endgroup\$ – Dmitry Grigoryev Feb 22 '16 at 15:53

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