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Old 09-09-2013, 11:50 AM   #1
ejonesss
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TiVo Power Supply Board for Premiere series 4 voltages

i have the series 4 tivo 746 and i was wondering what the voltages that the power supply puts out.

if someone has torn down a tivo series 4 and reverse engineered the power supply.

i know there is 5 and 12 and possibly 3.3 at the hard drive cable but i am not sure what the other voltages are.

if someone has a pinout on the power supply.

i suspect the reason for the symptoms of bad sectors is caused by a power supply on the edge of failure and is starving the system slightly.

i found at http://www.hobbyking.com/hobbyking/s...3uf_3sec_.html

basically it is a bunch of capacitors paralleled and as long as none of the pins exceed 15 volts i should be able to use these as a power stiffening device sort of like like why there are 1 and 2 f caps used in high power car sound systems.
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Old 09-10-2013, 02:26 AM   #2
unitron
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Quote:
Originally Posted by ejonesss View Post
i have the series 4 tivo 746 and i was wondering what the voltages that the power supply puts out.

if someone has torn down a tivo series 4 and reverse engineered the power supply.

i know there is 5 and 12 and possibly 3.3 at the hard drive cable but i am not sure what the other voltages are.

if someone has a pinout on the power supply.

i suspect the reason for the symptoms of bad sectors is caused by a power supply on the edge of failure and is starving the system slightly.

i found at http://www.hobbyking.com/hobbyking/s...3uf_3sec_.html

basically it is a bunch of capacitors paralleled and as long as none of the pins exceed 15 volts i should be able to use these as a power stiffening device sort of like like why there are 1 and 2 f caps used in high power car sound systems.
Please don't take this the wrong way, but you don't know enough to be doing what it seems like you're thinking about doing.


The TiVo uses a "switch-mode" power supply, which means the DC outputs have "ripple" that has a frequency in the thousands, if not tens of thousands, of cycles per second, and this means it needs what are called low ESR (Equivalent Series Resisitance) capacitors rated at 105 degrees C (which is above the boiling point of water) to handle those high frequencies and absorb any spikes caused by the coils which are also part of the setup.

That temperature rating, by the way, is not for how hot a room you can have the cap in, but for how high an internal temperature it can withstand. The job it does can result in internal heating due to current flow through what "resistance" it has, which is why that resistance needs to be low.

The thing you're looking at appears to have "regular" 85 degree C caps which are not low ESR.

It's designed to do an entirely different job in an entirely different device under entirely different circumstances.

Also, when capacitors are not yet charged up, they appear to a DC supply they are across as a dead short until they do charge and there's a lot of capacitance in that thing which will need charging up, so you could easily overload the supply.

And that's if there's nothing going wrong with the supply.

Judging by the picture here:

http://www.slashgear.com/tivo-premie...dware-2679242/

the power supply connects to the motherboard via a plug which you can back probe with a voltmeter.

Black will be ground, but if you've got an alligator clip you can put on the end of the meter's negative lead, better to clip that to the metal chassis on the side away from the power supply and only be holding the positive meter lead with one hand while keeping the other hand in your pocket.

The red wire(s) will be the +5V rail, the yellow the +12V rail, and if there's a 3.3V feed, it'll be an orange wire.

(the SATA specification has provisions for 3.3V on the power connector, but regular 3.5 inch hard drives, such as are used in TiVos, do not need it as of yet)

You'll note that the power supply itself is not separately shielded once you take the cover off of the TiVo (unlike, say, a PC power supply), and there are "straight from the wall socket-good for 15 amps of current AC" places on that supply with which you do not want to come into contact.


Series 4 TiVos don't seem to be subject to the "capacitor plague" problems to which so many S2 and S3 units have fallen victim.

But if you think there's something wrong with the supply, get a good repair shop to check the DC outs with an oscilloscope for ripple and the caps with an ESR meter and do voltage readings with and without the drive connected.

And have the TiVo plugged into a UPS when it's not at the shop.

And remember the very first rule of TiVos--

ALWAYS KNOW WHERE BOTH ENDS OF THE POWER SUPPLY CORD ARE AT ALL TIMES
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Old 09-10-2013, 05:01 AM   #3
ejonesss
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if there is nothing wrong then what causes the internal server to crash in the middle of a download?.

i suspected bat power supply also because many companies are using capacitors build on a stolen formula

http://badcaps.net/

it seems as someone broken into a factory of a quality cap maker and stole their formula.

unfortunately for all of us that was one of the flawed formulas that forced the maker back to the drawing board.

as a result capacitors fail or even explode on the board.
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Old 09-10-2013, 06:40 AM   #4
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If you really suspect the power supply is the problem you could swap it out. Weaknees has replacement power supplies for just about every TiVo model except the newest Roamio's.

http://www.weaknees.com/tivo-power-supply.php

I've done it and I'm no electrical engineer. I do dabble in computer building and network stuff so I'm pretty safe and the power supply swap was pretty easy and affordable to get an older Series 3 TiVo back in action.
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Old 09-10-2013, 03:13 PM   #5
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Quote:
Originally Posted by ejonesss View Post
if there is nothing wrong then what causes the internal server to crash in the middle of a download?.

i suspected bat power supply also because many companies are using capacitors build on a stolen formula

http://badcaps.net/

it seems as someone broken into a factory of a quality cap maker and stole their formula.

unfortunately for all of us that was one of the flawed formulas that forced the maker back to the drawing board.

as a result capacitors fail or even explode on the board.
What exactly are you trying to download when it crashes? And how is the Tivo being networked? The cause of that could be any number of things other than the power supply, including a seemingly "good" hard drive, your network connections, the Tivo firmware (did I really say that?), and even power line issues in your home.. On a P4, the power supply is definitely not the first thing I would suspect, and I have one of each: a 2-channel and a 4-channel. Yes, bad power supplies are an issue with older Tivos as Unitron pointed out, but they seem to have fixed the cap issue with the newer ones.
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Old 09-10-2013, 11:27 PM   #6
unitron
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Quote:
Originally Posted by ejonesss View Post
if there is nothing wrong then what causes the internal server to crash in the middle of a download?.

i suspected bat power supply also because many companies are using capacitors build on a stolen formula

http://badcaps.net/

it seems as someone broken into a factory of a quality cap maker and stole their formula.

unfortunately for all of us that was one of the flawed formulas that forced the maker back to the drawing board.

as a result capacitors fail or even explode on the board.
I'm quite familiar with the capacitor problem to which you refer.

(If you search the user names at the badcaps forum, you'll find mine)

It's known as "capacitor plague", and has been a problem since the late '90s.

You'll find more than one thread on this site about it as relates specifically to TiVo power supplies and the strange symptoms it can cause.

I had several BX chipset motherboards go bad because of it back in the Pentium II/III era.

I've repaired a couple of S2 power supplies and an S3 supply with the problem so far.

The monitor on which I'm viewing these words as I type them I grabbed out of someone's yard when they left it for the trashman, got a pre-packaged set of caps for that particular model from lcdalternatives, and repaired the switching power supply in it.

I didn't say there was nothing wrong with your S4 power supply.

I said what you proposed as a remedy was neither wise nor likely to work out the way you hope.


The odds of your problem being the power supply are much less than if you had a Series 2 or Series 3, way much less.

In fact if you had an S2 or S3 I'd tell you you were wasting your time troubleshooting until you had definitely ruled out the power supply caps, because the incidence of bad caps in the S2 and S3 supplies is so great.

But the S4 supplies haven't had the same failure rate or incidence of bad caps as the 2s and 3s by several orders of magnitude.

By all means check the supply with a meter and eyeball the caps for prefectly flat tops, but be open to the idea that the problem might have some other origin.


Remember, if someone else has already learned something the hard way, you might as well profit from their experience instead of going through the same thing yourself.
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