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Grumpy Old Man
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314 Posts
A Metal-Oxide Varistor (variable resistor) is supposed to have very high resistance, so high that it reads as if it were "open".

That only changes when there is a "spike", that is, a very high difference in electrical potential, a very high voltage, between the two places where it's connected, which is usually across the AC line.

120V AC actually varies (60 times per second) from 0 Volts up to about 170 Volts and then back to 0 and "down" to about 170 Volts but with polarity reversed from the first half of the cycle.

Only if something, like lightning somewhere vaguely nearby, for example, puts a spike up above say 300 Volts or so on the line does the MOV suddenly become extremely conductive, essentially shorting that higher voltage to ground at which point the MOV becomes very "resistant" again until the next spike comes along. The spikes are much shorter in length than either half of a regular AC cycle.

Generally a spike isn't strong enough to push much current, but the much higher voltage will burn out semiconductor junctions and that's how it does damage.

If you get a strike near enough that you wind up with scorch marks, that's not what I'm talking about, and that's something that the MOV wouldn't have been able to prevent.
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I have seen a MOV short out and since it's across the AC in I think it would be a good idea to remove it just for testing. I think he is going to have a hard time finding the short on this on. I had one that was popping fuses it was the Xformer shorted out and I have no idea where to find one. It would be nice to have schematic on this unit. By the way how have you been?
 

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Cranky old novice
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9,508 Posts
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I have seen a MOV short out and since it's across the AC in I think it would be a good idea to remove it just for testing. I think he is going to have a hard time finding the short on this on. I had one that was popping fuses it was the Xformer shorted out and I have no idea where to find one. It would be nice to have schematic on this unit. By the way how have you been?
MOV's also wear out as a function of the number and severity of spikes that they are exposed to. I believe they go open circuit in this case, which means there will be no obvious symptom (other than lack of protection).
 

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Grumpy Old Man
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314 Posts
MOV's also wear out as a function of the number and severity of spikes that they are exposed to. I believe they go open circuit in this case, which means there will be no obvious symptom (other than lack of protection).
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I have seen them short close. When my UPS got hit with a bunch of power surges I had two short so I make it a habit to take them out for testing. Of course with a dead short it could be anything.
I think the MOV that's on the market today is china junk. :mad:
 

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OTA is still alive
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529 Posts
I'm bumping this thread to make it easier to find 'cause I keep having to point people in the S3 forum towards it.
How about a mod making this a 'sticky'??
Shouldn't this be in the Series 3 sub forum in the first place?? ;)
 

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Wanted to say thank you to the OP. Because of your post I was once again able resurrected my S3 with lifetime.
How did you accomplish? Yourself, or did you find a service?

Looking for a reasonable cost(?) service for mine. :(
 

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I purchased the parts through Digi-Key and did it myself. It took about an hour to replace all of them. Make sure you have a good soldering iron, desoldering braid, solder and a magnifying glass.
Thanks. No exp with solder.

Will just do without until I can find a cheap service.
 

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My Series 3 is stuck in the reboot cycle. The history of my unit is that almost exactly one year ago, I replaced a bulging capacitor (C701) on the power supply and upgraded the drive to a 2TB (WD Caviar Green), performed the WDIDLE3 /D on it and everything worked fine for a year. I just opened it up and noticed another bulging capacitor (C601) and perhaps also C401 and the capacitor next to it. I checked the 12V supply (yellow) and it is 12.5 [good], and the 5V supply (red) and it is 5.15 [good]. I posted this first part earlier on the WDIDLE thread, but I have more information now, and I found the correct thread for this discussion.

I'm guessing one of two things is happening here:
1. Either the power supply has deteriorated and can't supply enough current for the drive and/or chipset.
OR
2. Somehow WDIDLE3 reversed itself recently and I need to perform it again on the hard drive.

I removed the hard drive (and took it somewhere with desktop access) and created a boot disk with WDIDLE3 on it and lo and behold when I checked WDIDLE3 /R, it seems to have reverted to 62 minutes (3720). So I ran WDIDLE3 /D and checked it and it's back to disabled. Then I brought the drive back home, reassembled everything and it still suffers from the reboot loop. Then I checked the power supplies again and they seem okay, but I also checked the 3.3V supply (orange) and it seems a bit low at 3.05 - 3.1V. So for now I disassembled the power supply and will take it to the office tomorrow where I can replace the offending capacitors (I have all of them [I think] because I bought a full set last year from DigiKey).

Have any of y'all seen a low 3.3V supply cause the endless reboot cycle? At this point, I don't think it's the drive because, one, it's only a year old (WD Caviar Green), and two, I just disabled the park mode. And if anyone has any further ideas, please reply.

If I can't fix my series 3, I have to choose a different TiVo and will need advice about that too. Is everyone going Bolt nowadays? Any way to get TiVo to transfer over lifetime service rather than springing another 600 bucks for it? (because if it's 600 bucks, it ain't gonna happen)

Thanks in advance!!!
 

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My Series 3 is stuck in the reboot cycle. The history of my unit is that almost exactly one year ago, I replaced a bulging capacitor (C701) on the power supply and upgraded the drive to a 2TB (WD Caviar Green), performed the WDIDLE3 /D on it and everything worked fine for a year. I just opened it up and noticed another bulging capacitor (C601) and perhaps also C401 and the capacitor next to it. I checked the 12V supply (yellow) and it is 12.5 [good], and the 5V supply (red) and it is 5.15 [good]. I posted this first part earlier on the WDIDLE thread, but I have more information now, and I found the correct thread for this discussion.

I'm guessing one of two things is happening here:
1. Either the power supply has deteriorated and can't supply enough current for the drive and/or chipset.
OR
2. Somehow WDIDLE3 reversed itself recently and I need to perform it again on the hard drive.

I removed the hard drive (and took it somewhere with desktop access) and created a boot disk with WDIDLE3 on it and lo and behold when I checked WDIDLE3 /R, it seems to have reverted to 62 minutes (3720). So I ran WDIDLE3 /D and checked it and it's back to disabled. Then I brought the drive back home, reassembled everything and it still suffers from the reboot loop. Then I checked the power supplies again and they seem okay, but I also checked the 3.3V supply (orange) and it seems a bit low at 3.05 - 3.1V. So for now I disassembled the power supply and will take it to the office tomorrow where I can replace the offending capacitors (I have all of them [I think] because I bought a full set last year from DigiKey).

Have any of y'all seen a low 3.3V supply cause the endless reboot cycle? At this point, I don't think it's the drive because, one, it's only a year old (WD Caviar Green), and two, I just disabled the park mode. And if anyone has any further ideas, please reply.

If I can't fix my series 3, I have to choose a different TiVo and will need advice about that too. Is everyone going Bolt nowadays? Any way to get TiVo to transfer over lifetime service rather than springing another 600 bucks for it? (because if it's 600 bucks, it ain't gonna happen)

Thanks in advance!!!
See my answer in the other thread and if you think you can't fix this TiVo feel free to give it to me. :D

As to transferring lifetime from it to another unit, the chances are probably as close to non-existent as makes no difference.
 

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If I can't fix my series 3, I have to choose a different TiVo and will need advice about that too. Is everyone going Bolt nowadays? Any way to get TiVo to transfer over lifetime service rather than springing another 600 bucks for it? (because if it's 600 bucks, it ain't gonna happen)

Thanks in advance!!!
Look at the Roamio Pro loyalty deal which you should qualify for. $600 for a Roamio Pro which includes lifetime service ($500 + $100 lifetime).

Scott
 

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Great thread, thanks for keeping it bumped.

I am in the process of replacing four caps, C401, C402, C601 and C701. Had a heck of a time getting some of the solder joints to melt, even at up to 780 Farenheit. In the end, I will have to drill out two of the more stubborn leads. I figure there must be some pretty effective heat sink attached to those leads.

Not that experienced with this, wish me luck...
 

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I think it was mentioned up thread but if you melt some new solder onto the tip of the iron it helps to get the original solder to melt. I had to work it that way when I replaced the caps in mine and this was the first time for me.
 
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