PDA

View Full Version : How do cable boxes work ?


edgerobber
04-07-2003, 01:35
I think the title says it all - I was wondering how that not so little black box works.
I have seen some mention of the workings in other threads, but I wanted an overall picture (non pixellated ;))
Some more specific random questions are :
[list=1]
Why does it put out so much heat ? - I know that any electronic equipment will get hot and it is passively cooled and all, but it does seem to get a bit hotter than my hifi kit.
How much power does it use ? The specs say 30W max, but anyone have any idea what the typical usage is ?
What does the power button actually turn off ?
[/list=1]
cheers

Mike Harrison
04-07-2003, 01:44
1) Digi cable boxes contain a huge amount of processing power to decompress the video stream. This takes power, most of which ends up as heat. There is also quite a lot of hogh-frequency analogue stuff in the front-end which takes a not-insignificant amount of power The need to build down to a price instead of up to an efficiency spec means they produce more heat than they could theoretically be made to, and don't dissipate it as well as they could.
2) ISTR about 20 watts when I measured one a while ago
3) Almost nothing - just toggles the select line on the TV SCART , turns off the UHF output and the display. Makes negligible difference to power consumption.

edgerobber
04-07-2003, 02:08
thanks - I thought that the power button didn't do much.
It seems a bit odd that the box doesn't have a standby mode, but it would probably be a "luxury" they costed out of the design.
I suppose the design to cost thing also explains the size of the boxes.
I wonder if there will be a complete cable tuner/decoder on a chip ?

spiderplant
04-07-2003, 15:44
Originally posted by edgerobber
It seems a bit odd that the box doesn't have a standby mode, but it would probably be a "luxury" they costed out of the design.

Not a luxury. The box needs to keep running to keep the EPG data up to date and keep the smartcard active. It means you can use the box immediately after coming out of standby. And it can wake up when reminders go off so you can make recordings. And it can look for software updates. And you can still use broadband. etc...


I suppose the design to cost thing also explains the size of the boxes.

The older models are full of components. And a big box helps with the cooling.


I wonder if there will be a complete cable tuner/decoder on a chip ?
Possibly, but two chips makes more sense. Then the same decoder can also be used in satellite and terrestrial boxes.

bob_a_builder
04-07-2003, 16:06
well now I'm confused - standby or not to standby

Originally posted by edgerobber
It seems a bit odd that the box doesn't have a standby mode

yet

Originally posted by spiderplant
It means you can use the box immediately after coming out of standby

Make your mind up !

MikeyB
04-07-2003, 17:16
I've seen a few posts about boxes getting so hot.

How comes a Sky Digital box doesnt get hot? Must be very similar technology used to decode the pictures. Mine never even gets warm at all.

zoombini
04-07-2003, 17:37
How do cable boxes work ?


Intermittently in NTL's case.

Chris
04-07-2003, 17:41
Originally posted by zoombini
Intermittently in NTL's case.

Well someone had to say it ... lol

Proppinupthebar
04-07-2003, 20:50
Originally posted by MikeyB
I've seen a few posts about boxes getting so hot.

How comes a Sky Digital box doesnt get hot? Must be very similar technology used to decode the pictures. Mine never even gets warm at all.

The cable box has two demodulators, one for the broadcast pictures etc and one for the return path, then also two modulators one for the RF feed of pictures to your TV, the other for sending back the return path info to the headend.

I think the modulators generate most of the heat.

darkangel
04-07-2003, 21:17
I Think that one of ntl's biggest problem is that pace cut corners, didn't specify adequate cooling how much of that is down to ntl I've no idea how many faults are caused by over heating boxes or dodgy eproms the die during updates etc must be quite a high number

Tristan
04-07-2003, 22:53
The usual figure quoted is that 1% of boxes die after every software update.

Don't know how many get fried because of overheating though. I wonder if if's possible to open the thing up and add one of those silent PC fans?

edgerobber
05-07-2003, 01:16
Originally posted by Tristan


Methinks Ntl wouldn't be too happy if you did that !!

Originally posted by spiderplant
Not a luxury. The box needs to keep running to keep the EPG data up to date and keep the smartcard active. It means you can use the box immediately after coming out of standby. And it can wake up when reminders go off so you can make recordings. And it can look for software updates. And you can still use broadband. etc...

I see what you mean, but even then things like the video decompression could be turned off (unless the epg is extracted from that ..) . I think what I really was driving at was that it should be to design a cable box that would use minimal power, while still keeping the basic functions active. For example it could be possible to have just one demodulator active and have it wake up the rest of the box (or even only the necessary parts) when the epg needed updating or smartcard checking etc.
To be honest I don't know, I just like bouncing ideas around.

Does anyone feel like doing some sort of simple schematic of how a box works ?

Plus - if the epg is on my cable box then why is it soooo slow ?

ppolo99
05-07-2003, 18:28
Cant they shove a fan in like a PC.

Suppose mabye more problems that may now i think of it.

Xaccers
05-07-2003, 18:54
Originally posted by ppolo99
Cant they shove a fan in like a PC.

Suppose mabye more problems that may now i think of it.

bearings go, fan rumbles, causes complaints etc

Now I wonder if you could take one of those huge AGP heat sinks and put it inside...

kronas
05-07-2003, 18:56
maybe they should install that huge fan/exhaust system they showed on the new geforce card :D :D :D

Tristan
05-07-2003, 23:12
Water cooling, that's the answer!

Proppinupthebar
05-07-2003, 23:33
Please do not give people ideas!!!!!!!!!!!!!!!!

ppolo99
07-07-2003, 00:16
LMAO, water cooling is great idea

Hell Fighter
09-07-2003, 21:52
Originally posted by Drudge
Sorry to butt in but we've had two Pace boxes for a good few years. They sit on top of each other in a little space under the TV. There's been no problems so far but is there a fire risk?

If by two Pace boxes you're referring to ntl STBs, then I wouldn't push your luck!

As far as I know you should keep them well ventilated, and you're not even meant to sit anything on top of them. That's why the install techs install the STB on top of your VCR/DVD etc.

- Hell Fighter -

meld51
09-07-2003, 22:14
x

th'engineer
11-07-2003, 08:17
It depends which type of NTL Toaster you have older 1000 boxes run warmer than 2000 or 4000 in my experience.
One of my family has just had a swap from 1000 to 2000, reason the smart card got toasted .
Its not that bad it was ex cwc original 1000 so it had a good life and gave good will carry on once a new card is made.

jemnery
11-07-2003, 09:43
Originally posted by ppolo99
Cant they shove a fan in like a PC.

Suppose mabye more problems that may now i think of it.

As someone who's tried very hard to build very quiet PCs, take it from me that passive cooling is great if you can get away with it. My educated guess would be that Pace decoders *just* get away with it - they can't be far off cooking their own components, especially in hot weather like this.

altis
11-07-2003, 10:23
Suggestion: pop the STB on its side so that the 'chimney effect' creates a draught and keeps it cool(er). I've tried this and it seems to work.

For block diagrams of an STB visit Broadcom (http://www.broadcom.com/) and navigate the products pages.

questocazzo
07-10-2005, 19:06
I'm sure my dilemma has something to do with the hurricane and electricity of some sort... I just want a detailed explanation of what's going on if someone knows.

Story: Hurricane came. Electricity was out for 10 days. Once electricity was restored, digital cable tv and cable internet worked fine. 3 days later, cable internet continues to work fine but the cable box on the tv won't come on. It's not like it comes on and just won't transmit cable tv, but the box itself just won't come on. Like the clock on the LED display won't come on just to show that it's plugged in (yes, it's plugged in).

I called my cable company and the lady didn't have a satisfactory answer and says crews are still around town fixing other hurricane damage right now and can't help me at this time (which is understandable). I just don't see how I can continue to receive cable internet but the cable box won't turn on.

Can anyone help?

deathball
07-10-2005, 19:17
how much does it cost NTL for one of these boxes?

Lew
07-10-2005, 19:59
Holy zombie thread, Batman!

As to your problem, it sounds like your cable TV box has died seeing as how you've said that "†¦the box itself just won't come on".