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Yesterday while trying to connect some cables, I brushed my chin on my receiver and got a mild tinge. I was concerned since the receiver was not plugged in. I got out my multimeter and pinching one probe with my fingers and the other on the receiver's chassis, I got a voltage of around 9V!! After many checks, I found out that this voltage came from my TV in standby via the video connector to the universal player and from the universal player via it's stereo out to the receiver!! (Video doesn't go through the receiver). When the TV was un-plugged, the voltage dropped to a very low value.Is this voltage normal? The TV is old and is rarely used. (But is still needed for an occasional movie or navigating DVD-A menus.) Can this voltage damage my equipment? Can this be suppressed? Surprisingly Charles Hansen had just talked about current leaking from TVs a few days earlier at the bottom of this post http://www.audioasylum.com/audio/general/messages/472085.html
Follow Ups:
Do you have cable or an antenna connected to the tv? If you have cable, disconnect it from the tv and check for the voltage again. If the voltage is gone then the problem is with the cable. If the cable line is not grounded properly then this problem will occur (actually a very common problem). If the voltage is only present when the cable is connected give the cable company a call and tell them to fix their line.
Thanks. I checked and the voltage is not from the cable. Actually it seems to be sinking some of the voltage. See my new test
http/www.AudioAsylum.com/audio/general/messages/472621.html
< < I brushed my chin on my receiver and got a mild tinge. > >This can definitely indicate a potential problem that should be investigated further.
< < I got out my multimeter and pinching one probe with my fingers and the other on the receiver's chassis > >
This is not a very meaningful or repeatable measurement. The normal way to measure is between the chassis and an AC safety ground. If your house is newer than about 1960, it should have 3-prong grounded outlets. Use the large "D" shaped receptacle as the ground connection. You will have to put the probe in at an angle to ensure that is touching the metal contact inside.
If none of the equipment is grounded (either because it all uses 2-prong power cords or because your house is old enough to not have grounded outlets), then it is not at all unusual to see 9 VAC between chassis and ground.
A good multimeter has 10 megohm input impedance, a cheaper one will have 1 megohm, and older analog meters may have 100 kohm. You can use Ohm's Law to calculate the leakage current. For example if you have 9 VAC and a 10 meg meter, the leakage current will be 9 / 10,000,000 or 0.9 microamps. This is not necessarily a problem.
< < The TV is old > >
How old is "old"? Are you talking a tube-type B&W set from the '60s, or what?
As suggested and with the input from "Bob in Alberta", I did new tests using the electrical outlet ground and the composite video terminal. (The TV case is plastic and so cannot check any where else). Here are the readings:
TV off, no cable: 0-0.1V
TV standby, no cable: 12V
TV on, no cable: 12V
TV off, cable: 2.0V
TV standby, cable: 8.8V
TV on, cable: 8.8VApparently the cable connection is sinking around 3V.
The TV is Sharp 20R-M10.
Any further insights?
I got this idea of measurement from one of Chesky's newsletter which talks about finding the correct power polarity for equipment.
http://www.chesky.com/core/body_librarydetails.cfm?newsid=156
I think the results are fairly repeatable but I will try again using the electrical ground. Yes I have grounded outlets but all my AV equipment do not use the ground. Do you think it is helpful to manually ground the chassis to electrical ground if it doesn't generate ground loops?I use a digital multimeter and I can check if the impedance is indicated. As mentioned in my reply to Al Sekela, last week I was testing a Harmon Kardon (demo unit) surround receiver but after one day of use it started shutting off. I'm not sure if the TV fried it. But the more probable reason is that the HK's cooling fan didn't work because on the first day it was running very hot and I could never hear the fan run.
The TV is a Sharp color TV, probably less than 10 years. It has remote and is multi-system capable. It is supplied by the owner of the house which I am renting.
It was not designed to be grounded, and doing so could cause a problem. As Charles Hansen said, if your meter is one with high input impedance, the voltages may not be abnormal for this type of device. However, I'd still worry about the fact that you felt the voltage through accidental contact with it.Are any of your audio components grounded to the AC safety-earth? If so, this leakage could possibly cause damage, and certainly is affecting your audio quality.
OK thanks, I won't try grounding it and create more problems. No none of my other audio equipment are grounded. I'll have to consciously keep turning off the TV (not standby) immediately after use.
Charles Hansen is talking about a different issue, the requirement that there be constant power consumption in any device that has a remote control ON/OFF function. A circuit in such a device has to be active to receive the "ON" command from the remote. The supply for this circuit may be a nasty little noise source that pollutes the audio system.Old TVs are dangerous for a number of reasons. They attract dust to the high voltage parts inside, and this dust can conduct enough electricity to get hot and catch fire. They also have capacitors across the AC line. These are what are called X-rated capacitors, in that they are supposed to be self-healing after AC line spikes. A few of them are not quite self-healing and start house fires. I've seen an estimate that several fires each year in the USA are caused by these capacitors. The longer they are exposed to the AC line, the more likely they are to fail.
The leakage you found may be due to a failing part inside the TV, or simple coupling through parasitic capacitance or mutual induction from the circuits that are under power when the TV is in standby mode.
If replacing the old TV is not practical, then set up a means to disconnect it from the AC line when you are not using it. Your audio system will likely sound better.
If you replace it with one of the new LCD TVs, be aware that some of these use noisy switching supplies. A good RFI/EMI power filter will reduce the pollution from the switching supply, which is always on. I don't know if plasma TVs have similar problems.
That's not possible because it's supplied by the owner of the house which I am renting. He will probably not replace it for "leaking power" and I don't use it much to buy one myself. It's a Sharp color TV probably 10 years old. Yes to reduce noise, I generally unplug it when listening to music. But when it is in use, like watching an occasional DVD, all my components (TV, universal player, receiver, speakers) are on and interconnected. I'm concerned about damaging the other components (which belong to me).
Last week I was testing a HK demo unit receiver and after one day of use it started shutting off. I'm not sure if the TV fried it. But the more possible reason is that the HK's cooling fan didn't work because on the first day it was running very hot and I could never hear the fan run.
Can you do a listening test with the TV connected, then completely disconnected? If you need one to operate your digital source, you might be better off with a small LCD unit and a good filter on the AC feed to it. Let the landlord keep his death-trap.
< < Charles Hansen is talking about a different issue > >Maybe, maybe not.
It's unclear from the original post what the actual situation is. But any modern TV has a switching power supply that is always running. And there is ALWAYS a leakage current onto the chassis that screws up both the sound and the picture when the TV is connected to the stereo system.
< < If you replace it with one of the new LCD TVs, be aware that some of these use noisy switching supplies. > >
They *all* do.
Plus LCD's look like crap compared to a good CRT. The best deal around right now is a Sony XBR970 34" widescreen for $1000 list. The picture will kick the crap out of any plasma or LCD, and for a lot less money to boot. The only thing is that it assumes that 34" is big enough for you, and that you can live with a TV that can't hang on a wall.
The Sony will also have a switching power supply, so you will still want to connect it to a switched outlet for critical listening.
LCD technology does not look natural to me. The blacks are way too saturated, and this seems to be a trend with the newer sets. I just picked up the new Sony KDS-R70XBR2. The SXRD is better than any LCD I've seen although some LCDs are brighter. The price to pay for this WAY to bright technology is that your eyes will hurt after only half an hour. I still have the Loewe 40" Aconda CRT set, and it is the best CRT I have ever seen. Doesn't have the amazing resolutioon of SXRD, but it is still head and shoulders above any CRT glass tube set I've seen.Of all the flat panel sets, I prefer plasma. To me it looks more natural. The Pioneer 1080p 50" set is amazing. I saw it a couple of weeks ago and was amazed. They just need to make a bigger version....
Thanks, Charles, I thought I was the only one left who hadn't drunk the Kool-Aid!
It had the super fine pitch tube, no longer made.I bought two!
Jeff
Yeah, but where are you going to get one? Hasn't been shipping for a year now...The last price for it was $1800. I'm not sure how much a used one would cost or how you would know its history.
Used ones pop up for around $500 or so.At that price you can have it professionally callibrated, and still have $$$ left over compared to buying a LCD/plasma.
The downside is that it is over 200 Lbs, and quite deep.
Jeff
Then it rolls around nice and easy.GTF
"The only thing is that it assumes that 34" is big enough for you, and that you can live with a TV that can't hang on a wall."The big negative for me is the 200 lbs. that it weighs. My wife can't help me lift it because she's only 5'0" tall. So I would have to hire someone just to move it for whatever reason after it gets planted.
Kurt
Then it rolls around real easy.GTF
GTF
To help a buddy out when he needs it. And sometimes it requires lifting.;o)
What are those? Not even my own brother would help me out lifting something like that. I once took his old TV to the recycling center and asked him for his help in getting it there. He saw all the extra brush and dirty stuff in the back of my pickup and he declined my offer to let him help me recycle his own TV for free. And that's the best friend I have. Friends, sheesh! Ya gotta do it yourself or pay to have it done these days.Kurt
Remember: friends help you move, real friends help you move bodies.
na
CRT's can hold a lot of static, enough for a zap for sure.I go near mine I can feel it tugging at my sparse hair ;-))
Just so long as it isn't letting out smoke, things without smoke don't seem to work real well.
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