TiVo Community Forums Archives - Power Supply Is Dangerous?

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Power Supply Is Dangerous?
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Posted by: bmcent1

I was reading Hinsdale's Upgrade How-to and was suprised at the number of warnings about the danger of touching TiVo's power supply.

I understand everyone wanting to protect themselves from any liability. But is the powersupply in the TiVo any more dangerous than the standard powersupply in a PC?

I've built many PCs and I've never worried about the power supply. I've even replaced PC power supplies. A TiVo unit is a custom PC running Linux and awesome application software. Why would the TiVo PS be so much more dangerous than a standard PC power supply?

If it truely is more dangerous, is there a way to safely (for the person, and for the TiVo) short the PS or drain the PS to eliminate residual current?

Posted by: cclaunch

It is more dangerous because PC powersupplies are enclosed in a metal box so that capacitors with potentially high voltages are not exposed where a hand could brush against them. The TiVo supply is a small board with components sitting out in the open. Furthermore, it is nearby where screws and cables will be manipulated in an upgrade.

Reasonable care will protect you -- the power supply is not jetting out arcs of lightning or anything but you could hurt yourself or damage the supply depending upon what came in contact with the open items.

Posted by: old7

A power supply in a PC is contained in its own case within the PC. The power supply in a Tivo, once the cover is off the Tivo, is exposed. Tivos were never meant to be user serviceable.

About draining the power supply, I wouldn't know why not, but that could be just as dangerous, if you slip or mess up. It is probably easier to be careful around it than drain it. If you can't be careful enough to do what little you need to do, then you probably shouldn't be draining it. For that matter, if you can't be that careful, leave the cover on the Tivo.

Old7

Posted by: Worf

Not to mention, it's a switching power supply, so those heatsinks sticking up from it are at a pretty high potential with respect to ground (80V or so). Plus some of those capacitors are at very high potentials (I think one of them has close to 150+V on it in normal operation - basically rectified AC).

And especially careful because the bloody Molex connectors can be a real pain to remove, and if you dont' stop yourself in time, your hand will fly into the power supply...

Posted by: mayweb

Yes, trust me, you will get a little jolt from the heat sinks....

Posted by: TimTrace

Amen, brother. I got hit last time I was inside my TiVo. I was jacking around with the hard drive and the underside of my forearm came down on some part of the power supply. BZZZZZZZZZZAP!

Posted by: kitsap

quote:
Originally posted by TimTrace
Amen, brother. I got hit last time I was inside my TiVo. I was jacking around with the hard drive and the underside of my forearm came down on some part of the power supply. BZZZZZZZZZZAP!

That is exactly what happened to me just yesterday (except I was fiddling with the fan connector). Underside of right forearm ... YOW!!!

Posted by: FUBAR

happened to me when i was cleaning my VCR once... So now i have another reason TiVo is better then a VCR... no tivo has shocked me yet.

Posted by: bmcent1

Okay, now I'm a little scared now ;-) ... well, I shocked myself with a phone line's 40V before, if TiVo's PS isn't much stronger than that then I'd be a little more assured as that was uncomfortable but not too bad. (However, I've heard that if you're really unlucky, catching a shock during a vulnerable period of your heart beat, the health consequences can be potentially... bad.)

** Back to the question of "draining the PS" before working on it... **

It seems that there are several "me-too's" here meaning people are getting zapped, cautious or not, sometimes a screwdriver slips, etc.

I used to play a lot more with electronics than I do now. Does anyone have ideas (or concrete experience) with building a little device to drain the stored charge safely (to the person and the TiVo ?) Could this be done with a few resistors, coils, or diodes?

TiVo, or repair shops that work on them, must have some way to safely discharge the power supply before fixing or refurbishing units. Ideas?

Posted by: kitsap

quote:
Originally posted by bmcent1
Okay, I'm a little scared now

Just be careful! The first time I ever opened a TiVo, I was extremely cautious and there was no way I could have gotten a shock. The danger lies with inattentiveness. It didn't happen to me until I'd poked around inside units MANY times ... it was definitely my own stupid fault.

Just pay attention to what you're doing ... which is probably how you'll act anyway, if you're digging inside for the first time.

[This is not legal advice.]

Posted by: Worf

What I normally do is on my SA TiVo (where the Molex connectors are within unplugging distance of the power supply - damned connectors!) is to reorient the wires so if my hand goes too far, I don't hit anything (generally good advice). As short as the wires are, they're long enough to actually unscrew the hard drive bracket, move the drive, and turn it away from the power supply.

And my distaste for those molex connectors - geez, make a more difficult-to-remove connector can ya?

Posted by: OzarkLad

It looks like I found out just how dangerous the power supply can be. While upgrading the hard drive in my HDVR2, I accidentally touched the power supply with the same hand as was on the hard drive, while the other hand was holding the case steady.

ZAP!

Immediately, the fan shut down and it's not doing a thing. Is it now a boat anchor?

If not, what sort of repair needs to be done? If it is fried, can I purchase a new HDVR2 and simply swap the access card and hard drive (being real careful this time!) and be set, or do I need to go through account signups and guided setup stuff?

Posted by: litzdog911

Another thing you can do to protect yourself is carefully insert some thick paper or a business card between the power supply components and the screws you need to remove. That way even if you slip you're less likely to zap something or yourself.

Posted by: Chris Gerhard

Wow, great information. As many of these things as I have opened up and worked on, I was not aware of the concerns. I will be more careful than ever with my next upgrade, hopefully the HDTV version.

Chris

Posted by: BlueXanaX

quote:
Originally posted by mayweb
Yes, trust me, you will get a little jolt from the heat sinks....

You know you are a tivo hacker when you have had this happen.
It only tingles for a few seconds. Hey why pay for ect treatments, the tivo is good for many things.

LOL

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