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Old 02-20-2006, 07:35 PM   #1
flybum
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Tivo 140 hr Series 2 Color Problems

My Tivo displays everything in black and white. The unit is 18 months old and has worked fine up until now. The color started fading in and out a couple of weeks ago and now is totally gone. It does the same thing on recordings or live stations. I have swapped cables, but it doesn't help. I have a lifetime subscription and this is very disappointing. Any ideas?
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Old 02-20-2006, 07:43 PM   #2
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Try switching which type of output you are using, like from S-Video to Composite or RF or the other way around. If using composite try switching which composite out you are using. That one output may have gone bad.
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Old 02-21-2006, 12:41 AM   #3
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or it could just be a bad s-video cable - if that's what you use.

Are the menu screens also b&w or is the problem only with recordings and live tv?
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Old 02-21-2006, 12:47 AM   #4
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He stated that he had tried swapping cables.
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Old 11-20-2007, 09:15 PM   #5
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The problem is a failed capacitor

I experienced the same problem on my Series 2 Tivo, and was able to trace the problem to C168 which appeared to have failed (C168 is a .1µF Ceramic Surface mount capacitor). Heating the capacitor was enough to get it into tolerance (the color would be happy), and freezing it would cause it to freak out and loose color.

It appears that C168 leads into the ML6428 (Y/C Video filter) the failed capacitor is on the C input. More information about the video filter can be found here - (the Product datasheet PDF)
http://www.fairchildsemi.com/an/AB/ABR-42018.pdf#page=1

The Y/C Filter feeds ALL of the unit's video outputs, so the failed componet makes all of the unit's video outputs lack a color signal.

The capicators are very tiny and are located on the motherboard in the area you would expect to see the video traces. They decouple DC coming from the video processor.

Note: The componet is VERY small and replacing it requires sodering skills, and is not for the faint of heart.

Replacement cost for failed part $1.50 (for a 10 pack of 0.1µF Surface Mount Ceramic Capacitors)

Last edited by johnreyn : 11-20-2007 at 09:20 PM.
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Old 10-09-2008, 02:21 PM   #6
Tcase420
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c168

The above post worked for me. I know this is an old thread, but thanks to the above poster. But just what he said, this is a tricky job. It took me about a 1/2 hour just to find the cap on the board with a magnifiying glass. For those who have never desoldered a surface mounted component, be very carefull not to over heat. It only takes a quick touch and your good. This was my first time. Fun yes. But nerve racking. Good luck to all.
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Old 02-09-2010, 10:04 AM   #7
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Quote:
Originally Posted by johnreyn View Post
I experienced the same problem on my Series 2 Tivo, and was able to trace the problem to C168 which appeared to have failed (C168 is a .1F Ceramic Surface mount capacitor). Heating the capacitor was enough to get it into tolerance (the color would be happy), and freezing it would cause it to freak out and loose color.
Thanks for the great information. I replaced the C168 and the removed capacitor tested bad. Unfortunately, it did not solve the problem. Any other suggestions?
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Old 09-28-2011, 12:38 PM   #8
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I wanted to jump in and provide some more information. I have a Tivo S2 model 540 as well that has had intermittent video problems for about a year now. It's been in the bedroom, so no big deal. I noticed however that it wasn't just going black-and-white, the contrast was getting out of whack also. I knew it wasn't "just" a lack of chroma information.

I finally got around to bringing it into the office today and having a look at it. I will attach some photos as well over the next couple of posts, some just for fun. Anyhoo, I replaced both caps (C168 and CC166). The old caps both tested at 0.1uF (well, one was at 0.99uF, certainly within tolerance). Replaced them both anyway. Both neighboring resistors measured (in circuit) at 150 ohms, 300 across them. (they're both load resistors to ground.)

The color problem with my tivo is a little different in that over time it will loose color (and no, changing cables does NOT help). rebooting the tivo sometimes fixes the problem. however sometimes rebooting causes the screen to loose sync completely and just look like a pile of jumbled mess! (will attach photos below)

Poking around with the unit on (DO NOT ATTEMPT unless you know what you're doing! I am a degreed electrical engineer with over 10 years experience. There are high voltages inside the Tivo, and if you fry something (yourself or your Tivo), I am not responsible!), I focused around the ML6428 based off the discussion found in this thread. I also attached an o'scope probe to one of the composite outputs and observed the NTSC signal waveforms. Most interestingly I found that if I touched the ML6428 side of C168 with my finger, the signal would degrade some. Remove my finger- signal remained degraded! This is unexpected behavior. Usually when you put your finger on a circuit it affects the circuit for as long as you're messing with it, and then when you "let go," it "snaps back" to proper operation like a tight rubber band. I reapplied my finger, signal on the o'scope almost went away completely (converged to GND). Eventually my small TV screen exhibited the "loss of sync" that we had experienced so many times at home. Now I was really on to something...

Kept moving my fingers around, and the signal "snapped back" unexpectedly. After some fiddling, and moving to a dental pick instead of my finger, I determined that touching the ML6428 side of C168 (or, ML6428 pin 4, chroma in, or CIN) caused the signal to degrade, and touching the ML6428 side of C166 (or, ML6428 pin 1, luminance in, or YIN) cause the signal to return. Both 150ohm load resistors are properly soldered and conductive to GND (and therefore each other), but they are on the input side of C166 and C168. It is the output side (the ML6428 side) of those caps that are having trouble.

I am supposing that the ML6428 chip might have gone bad. Newark has some available for $3/ea, however looking around I see that fairchildsemi has what looks like an improved version available (FMS6406) that I'm going to order as well and try, for about the same price.

ML6428 has the following "features"
  • 6.7MHz Y and C filters, with CV out for NTSC or PAL
  • 75 Ω cable line driver for Y, C, CV, and TV modulator
  • 43dB stopband attenuation at 27MHz
  • 1dB flatness up to 4.8MHz
  • 12ns group delay flatness up to 10MHz
  • No external frequency select components or clocks
  • 5% overshoot on any input edge
  • AC coupled input and output (ML6428CS-1)
  • AC coupled input and DC coupled output (ML6428CS-2)
  • 0.4% differential gain on all channels, 0.4 differential phase on all channels
  • 0.7% total harmonic distortion on all channels
  • 5V 10% operation
  • DC restore with low tilt

FMS6406 has the following (highlighting mine)
  • 7.6MHz 5th-order Y,C filters with composite summer
  • 14dB notch at 4.425MHz to 4.6MHz for sound trap capable of handling stereo
  • 50dB stopband attenuation at 27MHz on Y, C, and CV outputs
  • Better than 0.5dB flatness to 4.2MHz on Y, C, and CV outputs
  • < 5ns group delay on Y, C, and CV outputs
  • Equalizer and notch filter for driving RF modulator with group delay of -180ns
  • No external frequency selection components or clocks
  • AC coupled inputs
  • AC or DC coupled outputs
  • Capable of PAL frequency for Y, C, CV
  • Continuous Time Low Pass Filters
  • <1.4% differential gain with 0.7 differential phase on Y, C, and CV channels
  • Integrated DC restore circuitry with low tilt

There's also a FMS6410B:
  • 7.1MHz fifth-order Y,C filters with composite summer
  • 50dB stopband attenuation at 27MHz on Y, C, and CV outputs
  • Better than 0.1dB flatness to 4.5MHz on Y, C, and CV outputs
  • No external frequency selection components or clocks
  • < 5ns group delay on Y, C, and CV outputs
  • AC-coupled inputs
  • AC- or DC-coupled outputs
  • Capable of PAL frequency selection components or clocks
  • 0.3% differential gain with 0.2 differential phase on Y, C, and CV channels
  • Integrated DC restore circuitry with low tilt
  • Lead-free SOIC-8 package

I guess I'll get all three and just pick one. My guess is that I really won't be able to tell the difference with any of them. Once they arrive and I have a chance to try them, I'll post an update.

..dane

Last edited by audiodane : 09-28-2011 at 12:53 PM.
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Old 09-28-2011, 12:53 PM   #9
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now some pictures.. first, johnreyn indicated the caps are small. They're 0805 SMT caps. For comparison, the attached photo shows, from right to left, 1206, 0805, 0603, and 0402 caps sitting around my office. The smallest we use on a daily basis is 0402 (smallest pictured here). There are smaller still, most commonly used in modern cell phones.



Second, pic of the inside of the S2 model 540 tivo, with a red square highlighting where the ML6428 chip is found:



Last, a close-up of the ML6428 (U49) and the C166 and C168 caps. You can tell this photo is after the two caps have been replaced (nice shiny hand-solder blobs):



..dane
Attached Images
File Type: jpg IMG_0486_sm.jpg (94.8 KB, 105 views)
File Type: jpg IMG_0487_sm.jpg (173.9 KB, 104 views)
File Type: jpg IMG_0491_sm.jpg (173.2 KB, 104 views)
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Old 09-28-2011, 01:35 PM   #10
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Last some video images..

First is a great screen, with a great scope shot of the NTSC image:





Now, a scope shot "crushed" almost ALL the way down to ground.. Only a scope shot here, because there's not enough NTSC signal even present here for a TV to latch on to...



..dane
Attached Images
File Type: jpg IMG_0499_sm.jpg (138.0 KB, 97 views)
File Type: jpg PRINT_13.jpg (53.2 KB, 94 views)
File Type: jpg PRINT_12.jpg (40.0 KB, 96 views)
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Old 09-28-2011, 01:39 PM   #11
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And one "in between" shot.. Part-way crushed, but still just enough NTSC for a TV screen to attempt to latch to. On this particular photo you can see the screen can't even reliably determine the color burst sequence, which is making the colors all wonky. The color was actually flickering in-and-out while I was trying to take the picture.



here's one with the color completely gone:


Attached Images
File Type: jpg IMG_0495_sm.jpg (141.3 KB, 98 views)
File Type: jpg IMG_0494_sm.jpg (101.2 KB, 97 views)

Last edited by audiodane : 09-28-2011 at 01:44 PM.
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Old 09-28-2011, 01:57 PM   #12
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Temporary Fix?

Well on a whim, I thought I'd try "loading" the ML6428 side of each cap, since when touching it with my finger or the dental pick cause the problem to remain, it seemed to me like the problem may lie in the ML6428's improperly holding too much charge somewhere. Again I suspect it is a failed chip, but while I'm waiting for my new chips to arrive, I decided to try and "bleed off" any residual charge with a resistor.

And we're in luck, since the two load resistors next to each C166/C168 cap tie to ground, and the ground side is on the ML6428 side of the resistors, then it became real easy to just drop in two resistors, between the ML6428 and GND.

At first I chose 9.09K (1%), because 10K is a good number to start with (not TOO heavy a load), and I had 9.09K's laying around. But that didn't work. Composite output was completely grounded. SVideo output would occasionally try to display, but would quickly flicker back to black. 9K was too waaaay too strong a load. So let's up it by a magnitude.

Next I tried 100K (5%). 0603's fit nicely in the gap. See photo below. Result: SUCCESS! Image is stable. I can touch with my finger with VERY little effect. I can touch with dental pick with noticeable effect, but in both cases, when I remove my finger or the dental pick, the picture immediately snaps back to a nice full-scale signal! On some extremely crude measurements, it looks like I might be crushing the signal by around 20mV, which on a 2.3V scale (input side to ML6428), is just under 1%. This could easily be within the margin of error on my scope measurements too, however.

Anyway, I'll still order the replacement parts. But at this point, I probably won't do anything until more problems arise.

The pic below shows the two resistors that I added. One from C166 to GND, one from C168 to GND.



Granted these are small parts to work with, and I know what I'm doing. Still, if anyone else has any issues like this and any of the above is useful in fixing it, I'd love to hear about it...

cheers, and good luck!
..dane
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Old 09-28-2011, 11:33 PM   #13
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I'm only replying here so that I'll get notification of new posts.
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Old 09-28-2011, 11:48 PM   #14
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BTW, I believe you can subscribe with notifications without posting to a thread, right?
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Old 09-29-2011, 07:19 PM   #15
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Quote:
Originally Posted by audiodane View Post
BTW, I believe you can subscribe with notifications without posting to a thread, right?
I didn't see anything to click on, and all I can find in the user control panel is a setting that applies to all threads I start or reply to.

You don't happen to have TiVo schematics by any chance? (Do they even exist? It's not like there are repair shops that are part of their warranty service network who would have service manuals for them, like with TVs and stereos, or for that matter, refrigerators and washing machines.)
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Old 09-29-2011, 09:23 PM   #16
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I didn't see anything to click on, and all I can find in the user control panel is a setting that applies to all threads I start or reply to.
'Subscribe to thread' is found on the 'thread tools' drop down menu.
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Old 09-30-2011, 07:41 AM   #17
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Originally Posted by scandia101 View Post
'Subscribe to thread' is found on the 'thread tools' drop down menu.
..on the black bar immediately above the first post of the thread..

..dane
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Old 10-21-2011, 10:57 AM   #18
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Well, I finally got around to replacing the ML6428 with an Fairchild Semi FMS6406CSX. Scope-wise, there's no effect on the output signals when touching any of the inputs with my probes (or fingers)- YAY! Unfortunately it seems the chip is running a bit warmer than I'd like. I haven't gone to the trouble to calculate how much output current they're making the chip pump out, but that could be the culprit. In fact that could have been what happened to the first chip all along.

I ordered two from Newark for about $2.50/ea. I'm going to go ahead and close her back up and take her home and see how long she lasts. Could be a day, could be 10 years. Chips can handle a lot of heat, it's true. I'm just used to much more thermally conservative designs. MOST of the chips in the 540 S2 model run hot to the touch, in fact, so I suspect it's "by design."

(BTW, nobody seems to have any stock of the other chip I mentioned above.)

cheers,
..dane
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Old 10-21-2011, 07:51 PM   #19
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Quote:
Originally Posted by audiodane View Post
Well, I finally got around to replacing the ML6428 with an Fairchild Semi FMS6406CSX. Scope-wise, there's no effect on the output signals when touching any of the inputs with my probes (or fingers)- YAY! Unfortunately it seems the chip is running a bit warmer than I'd like. I haven't gone to the trouble to calculate how much output current they're making the chip pump out, but that could be the culprit. In fact that could have been what happened to the first chip all along.

I ordered two from Newark for about $2.50/ea. I'm going to go ahead and close her back up and take her home and see how long she lasts. Could be a day, could be 10 years. Chips can handle a lot of heat, it's true. I'm just used to much more thermally conservative designs. MOST of the chips in the 540 S2 model run hot to the touch, in fact, so I suspect it's "by design."

(BTW, nobody seems to have any stock of the other chip I mentioned above.)

cheers,
..dane
Allow me to suggest the addition of a hard drive cooling fan before you weld the cover back in place.

It may take a little finagling to find room for it, not to mention double-sided foam tape.
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Old 12-23-2013, 10:32 AM   #20
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What was final fix?

Quote:
Originally Posted by audiodane View Post
Well, I finally got around to replacing the ML6428 with an Fairchild Semi FMS6406CSX. Scope-wise, there's no effect on the output signals when touching any of the inputs with my probes (or fingers)- YAY! Unfortunately it seems the chip is running a bit warmer than I'd like. I haven't gone to the trouble to calculate how much output current they're making the chip pump out, but that could be the culprit. In fact that could have been what happened to the first chip all along.

I ordered two from Newark for about $2.50/ea. I'm going to go ahead and close her back up and take her home and see how long she lasts. Could be a day, could be 10 years. Chips can handle a lot of heat, it's true. I'm just used to much more thermally conservative designs. MOST of the chips in the 540 S2 model run hot to the touch, in fact, so I suspect it's "by design."

(BTW, nobody seems to have any stock of the other chip I mentioned above.)

cheers,
..dane
I have a Tivo series 2 TDC6490 that does the same thing, after about an hour of use every thing turns black and white after powering down the color comes back but only stays for about an hour and if I touch the caps in the area of the ML6428 chip for a couple seconds the color comes back and lasts about the same length of time.
So what was the final fix for your Tivo? Replacing the ML6428 chip the ceramic caps or both?
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