Electrical interference on screen when using external HDD media player

digital_frog · Member Joined: 12 Jan 2004 Location: Greece

Not sure if this is the right forum but here goes:

I bought a HDD media player about a month ago (a hdd enclosure with a TV out, decoder chip etc) and have consistently having problems with static on my TV (faint diagonal lines moving across the screen). I'm 99% sure it's caused by the rotation of the hard drive inside the box, but I can't figure out how to fix it.

Admittedly the HDD media player is pretty much a piece of c**p that was made god knows where in China, but otherwise it works well, so if anyone can think of a solution, i'd be grateful.

Thanks in advance,

DF

BJ_M · Patron Joined: 30 Jul 2002 Location: Canada

try using better cables or a ground loop eliminator
_________________
"Each problem that I solved became a rule which served afterwards to solve other problems." - Rene Descartes (1596-1650)

edDV · Posted: Jan 02, 2007 11:17

digital_frog · Member Joined: 12 Jan 2004 Location: Greece

Wow. Fast - thanks.

The power supply is a weird 5v/12v/ground that is only available from the manufacturer in China. Also, the machine refuses to display anything on screen when i try to use a better quality cable than the composite red/white/yellow cable that came with the device. So better cables unfortunately either aren't available or don't seem to work.

The problem is I know next to nothing (well, ok, absolutely nothing) about hum eliminators. If you could point me in the right direction as to where I might get a composite compatible hum eliminator online I'd really appreciate it.

Thanks again

DF

digital_frog · Member Joined: 12 Jan 2004 Location: Greece

@edDV

Sorry, didn't catch your post in time. The device is basically a no brand off ebay exactly like this one:

http://cgi.ebay.co.uk/3-5-inch-HDD-Player-Portable-MP4-MP3-DVD-AV ... dZViewItem

Yes, the interference does go away when I switch it off, and i didn't have any interference until I bought it and hooked it up to the composite input of my tv. The hum varies in intensity, often its only noticeable against a dark portion of the movie i might be watching, other times more intense with the bands being visible on a lighter picture as well.

Unfortunately I can't really separate the box and the disk as the circuit board inside has a very short ide and power cable, but I guess I could plug in longer ones from a spare computer and see if separating the two has any effect. If it does though, that means the box and HDD will have to be physically separate which kind of defeats the purpose of the HDD box in the first place

I was wondering actually if there's any way to better insulate the hdd inside the box (ie some kind of rubber mounting gromets) but not sure if that would have any effect. Any thoughts appreciated and thanks again.

DF

BJ_M · Patron Joined: 30 Jul 2002 Location: Canada

"insulate the hdd " will have no effect .....

standard cables should work if you have the cheapo red white yellow that came with it .... nothing special there ..

try moving the power supply around and see if the problem changes in intensity
_________________
"Each problem that I solved became a rule which served afterwards to solve other problems." - Rene Descartes (1596-1650)

oldandinthe way · Posted: Jan 02, 2007 13:52

Try connecting the power supply to a different circuit. Even if this means using an extension cord to reach another power socket. It is chaeap to try but probably won't eliminate the entire problem.

If the problem is RFI You may be able to gerryrig an RFI shield with tin foil to reduce the interference. Be careful not to interfere with air flow through the device.

edDV · Posted: Jan 02, 2007 14:45

Hum tends to move vertically because NTSC TV runs at slightly different frequency 59.94 vs 60Hz power.

Different crystal clock frequencies will cause diagonal or horizontal interference motion due to horizontal frequencies being slighly different as well. Usually, the cheaper the product, the wider the error in clock frequency and the more horizontal the motion.

digital_frog · Member Joined: 12 Jan 2004 Location: Greece

Looks like the socket was the culprit. The hdd box was plugged into a multi plug that was also running the tv, the home cinema system and a couple of dimmer switches.

The thing is i had it plugged in to a surge suppressor which is why it never occurred to me that the socket was the problem. I moved the surge suppressor with the plug to another socket an the hum is almost completely gone. Still a little bit left, but you have to stare really hard to see it.

Thanks a million to everyone for all the suggestions.

DF