TiVo Community Forums Archives - Exaggerated anti-hacking warnings?

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Exaggerated anti-hacking warnings?
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Posted by: Alonzo

Sites like 9th tee and others say, don't hack your TiVo if you aren't prepared, as one site remarked, to throw it in the trash if the hack fails.

Now, I understand that opening the unit will void a warranty. But I called Sony to find out if they would repair a TiVo that had a second drive added to it. They said that they would return the unit to its original condition for a flat fee (which is how Sony handles all or most of its service). The final word was, I should reverse all modifications before sending it in for service (which is easy enough to do). Then I could, for example, easily keep the second drive.

So, if what I learned is true, why the dire warnings against hacking? It appears that the worst that can happen is that I'd have to remove my second drive and pay the $130 or so to have the unit fixed.

Am I missing something?

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Alonzo

Posted by: vadimr

Not missing anything, just a regular disclaimer. Legal stuff you know. Someone lets say kills themselfs during the upgrade (how is it possible?) and then tries to sue tivocommunity.com (from the dead?) and tivocommunity.com will say we got a disclaimer.

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- Vadim
Visit my website (new uncensored TiVo hacking forum) ************.com

Posted by: Otto

quote:
Originally posted by Alonzo:
So, if what I learned is true, why the dire warnings against hacking? It appears that the worst that can happen is that I'd have to remove my second drive and pay the $130 or so to have the unit fixed.

Am I missing something?

Yes, you're missing that they are under no obligation to repair the unit for you, so if they tell you to "get bent", you basically have no recourse.

The whole idea of extreme warnings like that is so that, when someone whines and complains that they trashed their unit, every other hacker can look at them, point at the warning, and yell, "can't you read?!?" http://www.avsforum.com/ubb/biggrin.gif

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Everything I say is my opinion and not necessarily a statement of fact. Deal with it.
Otto, Zen TiVo Master - Moderator - AVS Tivo Forums - Tivo Underground, Tivo Coffee House
"The way of the portable computer user is as a stony path strewn with plugs and sockets, all the wrong size..." -- Terry Pratchett

Posted by: Scutter

quote:
Originally posted by vadimr:
Someone lets say kills themselfs during the upgrade (how is it possible?)...

Umm..unshielded power supply? http://www.avsforum.com/ubb/smile.gif

FP

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http://tivo.pineaus.com

TiVo Army of One
We record more before 9 AM than most people record all day.

Posted by: Delta

quote:
Originally posted by Scutter:
Umm..unshielded power supply? http://www.avsforum.com/ubb/smile.gif

But its just a little power supply, barely enough to give you a buzz. OK, maybe if you upgrade your tivo out in the rain or while standing in a bath tub full of water and accidentally (or intentionally) touch the right parts of the power supply then you might get a decent buzz http://www.avsforum.com/ubb/eek.gif

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Back to the old drawing board...

Posted by: sjf

Well, the main power line is exposed around where it enters the chassis, and around the fuse. That certainly is enough to give you a tingle! But you would have to be REAL fumble-fingered to accidentally brush up against that while doing anything usefull inside the box. Others have claimed that 'lethal' voltages are present in the supply even when the power is removed. I would suspect that any voltages of that type would be dissapated fairly rapidly once power is removed. (But don't come crying to me if it electrocutes your cat -- or wife, for that matter).

[This message has been edited by sjf (edited 06-25-2001).]

Posted by: Delta

quote:
Originally posted by sjf:
Others have claimed that 'lethal' voltages are present in the supply even when the power is removed. I would suspect that any voltages of that type would be dissapated fairly rapidly once power is removed.

Actually the larger capacitors can hold a good and painful charge for days, but other than a good blister/burn mark there is nothing lethal once unplugged. The reason is that that the current has been removed.

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Back to the old drawing board...

[This message has been edited by Delta (edited 06-25-2001).]

Posted by: ZEROTrace

hmmm, if they charge around $130 for a repair, which would most likly be a 'new HD' i wonder if they would sell a 'backup drive' for the same price?

-ZERO

Posted by: Worf

Well, the main problem is the main switching supply. A switching supply, in contrast to a regular linear supply, works by first converting the AC input to a DC voltage. This DC voltage is then stored in a capacitor (voltage = peak AC voltage, which for 120VAC, is around 160 V or more). This DC voltage is converted to a high-frequency AC voltage through the use of a stadnard H bridge configuration and controller. Finally, the voltage is stepped down to the requisite voltages, rectified again, and output. The nice thing is, you'll find most supplies are dual voltage, since the controller alters the H bridge pulse widths, ensuring the output it's measuring is within range (i.e., it's automatic by nature of closed-loop controllers).

So there's a particularly nasty high voltage available for at least half of the supply. Oh yeah, the transistors used in the H bridge often have either their input or output pins (never the control) connected to the heatsink, resulting in the high voltage being available at a bare surface.

However, if you unplugged your TiVo, it's quite likely that the voltage stored on the capacitor is lower, but still quite high (i.e., the controller lost power before the capacitor did) -- switching supplies tend to operate unregulated until the controller kicks in (chicken-and-egg: the controller needs power to operate the power supply, but the power supply needs the controller to provide power) and begins regulating the output. Of course, switching supply design is fairly interesting, requiring events to happen in a certain order before the supply works -- if it doesn't, it goes *boom* http://www.avsforum.com/ubb/smile.gif.

I believe someone measured the voltages available, and it came out that the heatsinks had ~ 80V or so...

And anyhow, a small burn/blister will still be a liability -- if someone hunched over their TiVo, and their necklace touched the heatsink and grounded their pacemaker... (remember, in today's legal environment, if anyone can even get a cut, they'll sue!). Or if they accidentally spill their Coke onto the supply and cause some sparks that cause a fire...

Oh yeah. The insides have some pretty nasty sharp edges...