I've had Comcast's combo HD/DVR box (the Motorola 6208) for a few months now and have had many problems. Some I attribute to Comcast's service (e.g. a lot of tiling on a few of the HD channels), but most I attribute to the Motorola box. The box freezes a lot, requiring me to unplug it in order to reset it. There doesn't seem to be any rhyme or reason to when it freezes. Thankfully, I don't lose anything I've recorded. But, the biggest problem which seems to be a mystery to Comcast, Motorola, Monster (I use a Monster Power Center), Samsung (I have a 56" DLP), and Tweeter (where I got the Sammy) is the following:
I leave the cable box on all the time and just turn the TV on and off like most people. All components in my system (including VCR, DVD Player, HTIB Receiver, and PS2) are plugged into a Monster Power Center as is the cable coming in from the wall. About 60% of the time, when I go to turn the TV on, within a few seconds, the cable box shuts off. It can't be turned back on from either the remote or the box itself and must be unplugged and then plugged back in to reset. I already replaced and upgraded the power center and that didn't do it. The cable box is not even warm, so it's not that it's overheating. And, at one point I even disconnected anything directly connected between the cable box and the TV and it still happened. No other component I have is affected, and the problem never happened when I had the regular HD box (before Comcast swapped it for the DVR unit). Not only that, but I've even had Comcast replace the DVR box with a new one, to no avail.
Neither I nor anyone else I spoke to can think of any reason why the cable box should even 'know' that the TV power is on or off. Is it a power surge? Is the cable signal somehow bouncing back through the cable when the TV is turned on? I'm lost. Anyone got any ideas?
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I would bet it's power draw from the TV causing the cable box to 'brown out'. Can you temporarily connect it to a different outlet or preferably a different circuit (maybe with an extension cord)? That would definitely isolate the problem. You could also measure the voltage drop with a volt/ohm meter to verify. Which power center do you have? Is it suppose to condition the power or is it just a surge protector?
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Thanks for the suggestion. To answer your question, I'm using a Monster Home Theatre PowerCenter HTS 850 w/ Clean Power Stage 1 V2.0. I know it filters the power and provides surge protection, but I'm not sure if it also regulates power. I did at one time plug the cable box into the wall (a different outlet than the power center was plugged into), with the TV still plugged into the power center and it still happened. Then, I tried plugging the TV directly into the wall (same outlet as the cable box) and the problem didn't happen. That's when I assumed it was a problem with the PowerCenter and replaced it. But, as the problem kept happening with the new PowerCenter, I figured that wasn't it and it was probably just a coincidence that when I plugged the TV directly into the wall the box didn't shut off (since it only happens about 60% of the time). Could the TV be drawing power such that the box in a separate outlet mid-way across the room goes out when there's a good distance, another outlet and the PowerCenter in between the two?
If that is the case, which item would you say is defective? The PowerCenter for not regulating the power, the TV for drawing too much power, or the cable box for being too easily affected by additional power draws? Or, do you think it's an electrical problem in my home? I would still think it's the cable box as I had no problem with the non-DVR HD box.
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Remember that it's all one circuit regardless of how many outlets there are or where they are. The voltage drop would occur on the entire ciruit so location wouldn't matter much. Running an extension cord from a different room should put it on a different circuit and allow you to test that theory. If it works then you know it's the circuit load.
It sounds to me like the DVR is too sensitive to the voltage drop. I checked all the regular Monster power conditioners and they are not voltage regulators and probably won't help. The AVS2000 is a voltage regulator but it's $1500 retail. It would probably be cheaper to run another circuit for your TV or cable box (once you're sure that's the problem). That will also help your receiver performance.
You could have a problem with the TV but they normally draw a lot of power at startup (do your lights dim?). I think the cable box is too sensitive. You might be able to find cheaper voltage regulators also but i still think running a separate circuit is your best solution.
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I agree with akirby that a voltage dip is occurring, and it is caused by the current surge when the TV is turned on. His suggestion to plug the cable box (or TV) into a different circuit is a good test. But if this fixes the problem, there is a hidden risk in leaving it that way: ground loops. Ground loops cause a variety of problems, often subtle, that are typically hard to understand and fix. In the end you want all the units of your home theater to be on the same house breaker, if at all possible.
Although the cable box is at fault, redesigning it is not one of your options. Your first challenge is to determine whether the power center or the house wiring is responsible for the dip. Both will contribute some to the dip, but likely one is contributing a lot more than the other. Try 1: plugging the cable box directly into the wall (same breaker, but bypassing the power center), and 2: plugging the cable box into a different circuit (different breaker) via an extension cord. If 1 fixes the problem, you need a beefier power center. If only 2 fixes the problem, the house wiring is inadequate, which would require you to either move non-theater appliances off that breaker or have an electrician rewire that circuit with heavier wire.
You have already performed experiment 1. But you did it two different ways and got conflicting results. (Experiment 1 can be moving either the TV or the cable box to a wall socket.) No logical conclusion is possible. You have to figure out which version of experiment 1 was done wrong. Pay attention to non-theater appliances on that breaker.
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Ken - why would they need to be on the same circuit (I assume that's what you meant by breaker)? Wouldn't it make more sense to run 2 dedicated circuits - one for the TV and one for the other equipment?
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First off, I really appreciate the input from both of you(and Allen, I particularly appreciate you researching the Monster PC functionality as that was above and beyond just your opinion).
To answer one of the questions raised, I do not see a dimming of the lights or any other visible impact from powering on the TV (including any dimming of the displays for my VCR, DVD Player or Receiver).
I guess I'll try plugging the TV and cable box into the wall directly again first to see if the time I did that before without a problem was an aberration (I only tried it once, so as the problem happens only 60% of the time, I'll turn it on and off several times this time). If that solves the problem, then the issue must be with the Power Center, right? But, how could the PC itself be drawing additional power away from the cable box if it doesn't regulate power in any way? Also, if getting rid of the PC is the answer, aren't I exposing my equipment to risk and losing the benefit of "clean" power (unless that's just BS)?
If I do get a shut off again with that, then I'll try the extension cord into another room. If it turns out that there's no problem when the TV and cable box are on different circuits, then what would you suggest as a long term solution? In order to keep the $150,000 warranty provided by Monster, everything has to go through the power center. Even if I can fix it with electrical wiring, I don't want to pay someone to tear up my walls and change my wiring if someone else is really at fault (e.g. Samsung or Motorola). But, how would you conclusively determine whether it's the wiring that's insufficient, the box that's too sensitive or the TV that's drawing too much power?
Again, thanks for all the help. It's been more informative than anything from any of the "professionals".
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Allen: I guess you haven’t wrestled with a ground loop problem. They aren’t all that common, but when they occur they are fiendishly difficult to deal with, even for me, an engineer.
Typically, when a two-circuit solution is employed, everything initially looks fine. But a few weeks later the viewer notices some very faint shadows and other barely detectable flaws in his picture. He didn’t notice them when the system was set-up, and now that he does, he doesn’t attribute them to the last change he made. Instead he will think one of his units has gone bad. He will substitute new units into his system, but the shadows never go away. He will conclude that his supplier is sending him bad units. Every decision he makes will likely be wrong.
Average Joe is hopelessly outmatched by problems like these. The only wise advice is to follow a rule that prevents them: Put everything on one circuit. That said, if Blev adopts a two-circuit solution there is a good chance he will create no ground loop artifacts.
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Blev: To understand the voltage dip you must keep Ohm’s law in mind: voltage equal current times resistance.
Circuit breaker resistance = 0.1 ohm (These numbers are all wild guesses.)
House wire resistance = 0.3 ohms
RF Filter resistance = 0.5 ohms (The RF filter in the power center probably employs coils.)
-------------------------------------
Total resistance = 0.9 ohms
Assume the TV plugs into the power center. If the TV inrush current is 20 amps then the voltage over the total resistance is (20)*(0.9)=18 volts. This is subtracted from the line voltage: 117-18=99. Thus the voltage at the TV dips to 99 volts for a fraction of a second.
You can’t redesign the cable box. But if you reduce some of the resistances above, the voltage dip will be smaller and the cable box might ignore it.
This message has been edited by KQ6QV on Apr 14, 2004 5:07 PM
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So, are you saying I should reduce the resistance by getting rid of the Power Center? I'm hesitant to do that because of the risks to my equipment from not using proper protection, not to mention that my picture will be worse without "clean" power (i.e. if it's not filtered through the Power Center). Unless those claims are just overblown marketing hype from Monster? Do you typically recommend using a power center like this?
I'm also hesitant to create a ground loop since based on my luck with electronics lately (another story), I'm sure I'll have whatever problem can arise from a ground loop and it will drive me insane. Plus, the cost of creating a dedicated circuit for the TV is not something I want to incur.
Maybe I should get a separate PowerCenter just for the TV? Do you think that would do it?
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Blev: Are Monster products all hype? Definitely. Maybe one out of twenty Monster products is improving anything. But, even knowing this, I bought a big Monster power strip for my TV. After spending $15,000 for my system, the cost of the strip was of no concern. I think of it as insurance.
Unless thunderstorms are predicted, there is no risk in running your TV without the power center for a few days. If the cable box still shuts down then the house wiring is where most of the resistance is. If it doesn’t, one option is for you to get a second power center, just for the TV.
In theory, there is a device that will make a house rewiring unnecessary: An Inrush Current Limiter, which would go in series with the TV power cord. It would reduce the inrush current by spreading it out over time, and that would reduce the voltage dip. But nobody seems to make them. I searched the web for an hour and found only one unit, made in England, for 230 volts.
Most surge suppressors just clip the top off of voltage spikes. But there might be some that limit surge current. If you can find one that limits the surge current to about 10 amps, it would probably serve as an inrush current limiter.
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If you want this to just stop sounds like another surge supressor strip is in your future. You don't have to buy the Monster but make sure it meets the requirements as layed out.
If you want to take another stab at it then read this. Might be good idea anyway.
I am suspiscious of a potential ground loop or RF inteference. I am referring to...
from the thread
"Annoying Ground Loops
Most consumer equipment does not have the ground pin but some do and depending on your application may be the source of a ground loop. First step is to understand that every electronic product..."
Richard F. Fisher
Have you been calibrated? ISF and HAA Trained
Mastertech Repair Corporation, Lawrenceville, GA
770-513-3987 E-Mail - help@mastertechtv.com
Factory Authorized Service
Mitsubishi, Hitachi, Toshiba, Harman Kardon, Infinity, JBL
Lumagen Scaling and Bravo D1 Dealer
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I meant isolate it to that circuit by putting the cable box on another circuit to see if it's the voltage drop. Maybe there are other possibilities like ground loop or RF interference that it won't isolate.
Sounds like the easy way is to add a different surge protector to the TV. Very easy and not too expensive to try.
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Blev: There is a $50-$100 alternative to replacing the house wiring: Power the cable box via a small computer UPS (Uninterruptible Power Supply). Since there is a possibility of a switching-noise problem, the UPS should plug into a wall socket, not the power center.
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Sorry all for disappearing while you worked on my problem. I've been out of town for a bit. Thanks for all the input. Richard, thanks for the links on grounding and surge protectors. My setup seems to be square with the requirements you laid out (all components going through the power center (which has a 3 prong plug into the wall, including the cable line, power center came with insurance, and I'm pretty sure covers lightning). Ken, thanks for the idea on the UPS. I'll probably try that and/or a second Monster power center just for the TV (or just for the cable box).
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I've been reading through this thread and perhaps I'm an idiot (wouldn't be the first time I've been accused of such ) but there may be a much simpler solution. Is it a requirement that you leave your DVR switched on all the time ? If not then I suggest you try powering down the DVR + TV, power-up the TV and then power-up the DVR. If that works out ok you can very easily program a macro sequence in a programmable remote to do that each time you want to watch TV. Perhaps this is all a non-option for you but I thought I'd suggest it just in case ....
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How about some problem in the video conncections? How is the STB connected to the TV? Component or DVI? When the TV comes on the video circuits in the TV have to sync with the video from the STB. Maybe part of the time the STB cannot establish a proper connection and freezes like when a computer freezes due to an internal data error. This is Richard's territory.
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Brendan, thanks for your suggestion. That probably would take care of the problem. But, I'm looking for a solution rather than a workaround (mainly due to my own frustration for not knowing what the problem is).
I'm using component cables to connect the STB with the TV. I've been wanting to switch to DVI, but haven't been able to confirm that the DVI connection on the STB is actually enabled (I've seen some posts on other boards saying it is, but Comcast says it isn't and I didn't want to spend the money until I knew I could use the cable).
The way the problem presents, it certainly seems like it has something to do with the signal, rather than the power because it often takes a few seconds before it shuts off and in some cases rather than shutting off, it just freezes. I've just discounted that theory as I couldn't think of any reason why the STB should "know" whether the TV is on or off.
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) but there may be a much simpler solution. Is it a requirement that you leave your DVR switched on all the time ? If not then I suggest you try powering down the DVR + TV, power-up the TV and then power-up the DVR. If that works out ok you can very easily program a macro sequence in a programmable remote to do that each time you want to watch TV. Perhaps this is all a non-option for you but I thought I'd suggest it just in case ....