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Strangest problem
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Posted by: snoop

I've updated the fans in 4 of my 5 tivo's with no problems. I recently went to upgrade the fan in the 5th and had the following results:

For starters I was surprised to find a Papst fan set for 7v in it, and its the original fan. All the other tivo's i've worked with were running a panaflo at 7v. In fact, the papst at 7v turns a very small volume of air, much less than the panaflo does. That explains why that one was always 3c warmer than the others.

I replaced this with a papst 12v fan, identical to the original except for a 12v connector (in line with one of the hard drives) instead of the 2 pin 7v connector.

It worked fine for about an hour, and much more air flow could be felt from the back. The temp was a lot lower.

An hour later, I was watching a show and the colors all went flooey. Blue was purple, other colors were all skewed. I opened the box and checked wiring and whatnot, fingertip tested the chips for temp, everything was cool, nothing was touching anything wrong. Powered up, all was well. 10 minutes later, same problem. While I was thinking it over the unit tripped from the menu's to live tv and I got the blue-screen 'cant get live tv' thing. I power cycled and it was well again but couldnt get live tv. Ten minutes later the colors on playback skewed again. I could get tv signal on the tv when the power was pulled on the tivo.

I pulled the 12v fan and put the 7v back in, all was well and has remained well for 3 days now.

One possible explanation for the livetv problem was that we had a complete rain deluge that went for about 15 minutes. Perhaps as a complete coincidence that knocked my cable signal down and while the tv could handle the lower signal the tivo couldnt. I've seen that happen before.

The color skew completely flummoxes me. Could it be a 12v problem with the power outage that the minute draw from the fan produced? Perhaps some junk signal distortion the fan injected into the 12v supply?

I may try this in another tivo to see what the results are, or I may re-introduce it into the same tivo and if the problem comes back, try another power supply.

Anyone else see anything like this? Only color problems i've heard of in the past were flakey decoder chips when they were hot, which wasnt the problem here.

Posted by: weaknees

Pretty interesting - what exact model TiVo is it?

Michael

Posted by: snoop

Its an HDR-112, one of the old Circuit City $99 specials from about 2 1/2 years back. Its got a seagate 80gb as the 'a' drive and an lct15 (one of the 4400rpm versions as its 'b' drive. Been running like that for a couple of years with few problems. Only outstanding quirk is if you go into 'search by title' and spend a fair bit of time in there picking shows, after 15-20 minutes the tivo will freeze and has to be power cycled. Curiously, my very first tivo, an hdr-312, did exactly the same thing and I had to send it in to philips for a refurb. Havent seen this symptom on any other system.

Its still running fine with the 7v papst fan back in there. I havent had the time to try to reproduce the problem with the same or a different unit.

Nice temp difference though, that papst at 7v moves less air than the panaflo does at 7v. My temp dropped from 32c to 26c. I'd like that extra air flow for this summer when the temps head into the 90's.

Posted by: zaknafein

If I were guessing, it sounds like your PS can't handle the extra load at 12v, and is causing your hard drives to wig out.

Posted by: snoop

Perhaps. The fan doesnt pull much load though. I'm just glad the damn thing is working again, I thought for a few minutes that perhaps the new fan had frozen and the whole thing had overheated. The symptoms looked at first as if the tuner and decoder had both gone south.

When I get over the "omigod is it dead" thing I'll try it again and if the problem recurs I'll drop another power supply in there and see if its better.

Posted by: Chris Gerhard

quote:
Originally posted by snoop
Perhaps. The fan doesnt pull much load though. I'm just glad the damn thing is working again, I thought for a few minutes that perhaps the new fan had frozen and the whole thing had overheated. The symptoms looked at first as if the tuner and decoder had both gone south.

When I get over the "omigod is it dead" thing I'll try it again and if the problem recurs I'll drop another power supply in there and see if its better.

Could you have a bad Y power connector? It sounds like a power problem to me and not a tuner or decoder problem.

Chris

Posted by: snoop

Possibly. Although that wouldnt explain why it worked for up to an hour.

If it was a physical connection problem or a noise induction situation, i might have expected it to manifest promptly and persistently, although I know some things can degrade due to thermals or increased resistance over time...seems like a longshot here.

One thought I had was the fan had a long power lead and I tucked that down by the drives and power supply, and the 12v pigtail was also a little long so I tucked one end under the edge of the motherboard down in front of the fan. So induction of some noise was on my mind...but again I'd have expected more immediacy and persistence to the problem.

I've copied the season passes from this one to another, when I get a few days worth of duplication i'll pull that flakey one and poke it with a stick until I figure it out.

The good news (for some) is that what appears to be a dead tuner and/or motherboard problem may be something far simpler...as soon as I figure out what it is...

Posted by: snoop

Well heres the post mortem. I wish I had step by step tried to repro the original problem but I dove directly into fixing stuff without knowing what was broken, but this turned out to be an ok thing.

I replaced the power supply in this series 1, put in the new fan, blew out the dust and fired it back up. No problems after 3 days of steady use.

Here's what I think the problem was. The morning after I replaced the power supply (left it on the kitchen table - the benefits of being single are many), I sat down for breakfast and noticed a puddle of dried pale yellow spooge around the base of the cluster of capacitors next to the hard drive connector on the supply. I checked my other spare supply and another series 1 with the original supply and no goop, so I presume its leakage from one or more of the capacitors. It was light yellow, had some bubbles in it, and it was hard enough to need a razor to scrape at it. There was a good bit of it, it was about a 16th of an inch deep around the caps and on a few was 1/4 of the way up the sides.

So my guess is that when I updated the 7v fan to 12v, the 12v supply was running out of gas due to a lost cap, and this led to bizarreness.