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Discussion in 'DirecTV TiVo Powered PVRs & Receivers' started by mikeandnikki, Dec 28, 2006.
CCS corp will fix the tuner. http://www.ccscorporation.net/dss.htm
they fixed mine
Check the remote filter caps on the main board.
these "smt" elecrolytic capacitors might not be bulging in order to test bad. It is less likely they would. In this case "remote" means remote to the power supply. The capacitors are in tandem with the capacitors that have been mentioned as being a fix in the power supply itself. If either degrades the other will pick up some of the slack and work harder and either failing can produce a similar effect. So if blindly replacing the power supply does not help, it would be an oversight to not consider these other capacitors on the main board that provide the same function (which is to bypass fluctuations in the power supply voltage- ie ac - to ground). In all the research I have done on this problem I have barely seen this idea mentioned, and even then not quite.
Edit: Ok looking at this further I can present a better idea of what I think is causing the basic problem. First, by way of explaining the failure mode, the video filter chip which converts the final signal into both composite and s-vhs outputs shares it's power source regulator with tuner2. Tuner one is on a separate regulator circuit. For whatever reason the video filter chip requires a higher degree of decoupling than it did when the unit was new. Exactly why I don't know yet. Anway preventing the ac currents from the video filter from feeding back to tuner2 is what is required here. This is also the concept of the bypass capacitor I mentioned above. However those capacitors are too far from the video filter to achieve the desired result here (although they might help mitigate it if it isn't too severe- like replacing the supply did at one point). The fact is the filter chip already has it own decoupling capacitor associated with it. So far, what I have done by way of experimentation is increased the value of that capacitor to decrease the impedance of the ac path to ground (that's how decoupling works basically). Note impedance is a function of frequency. The value I used (by chance) yields the result that almost all pixellation (and all the seaching for sat messages) dissappear. Also the signal strength meters stop fluctuating on all transponders and all 3 satellites. The only thing I need to do is to eliminate the last bit of pixellation on the few remaining channels that still have it. This should just be a matter of fine tuning this solution. I might end up cutting off the 5 volts source from the regulator to the video filter and supply that filter chip power from the 5 volt output of the main supply instead (note the way it was designed is the 5 volts for the tuners is derived on the main board from the main 12 volt supply output).
For an indication of how involved I got with finding the source of the problem, I was able to obtain a new tuner chip and I replaced tuner 2 (yeah I know that was a tall order - but I did it). So the tuner chip is not the problem. I might also speculate that replacing the video filter chip might have an effect or even fix the problem completely without the need for any other solution, but that chip is totally unavailable and is a proprietary D*TV design. It would be nice if someone would try taking that chip from a unit that does not exhibit this problem and transplant it into one that does to see if that is the real culprit.
I really do not advise messing with this stuff unless you know what you are doing. Surface mount components are a bit (ok a lot) tougher to work with that the capacitors in the power supply that were shown to be a fix at one point.
One remaining question: how far does this problem go if it continues to degrade? what is the end point? Is there a final fix short of finding and repairing the root cause? I realize these unit are pretty old now but I think I can get a lot of use out mine yet.
If you experiment with alternative parts in place of the capacitor I mentioned they should be sized appropriately and the should not be connected with runs of wire of any real length to speak of. I am relatively confident that a good part of the interference with tuner 2 has to do with radio frequency interference and/or electromagnetic interference caused by induction and feedback of these currents from the video filter circuit. I had no luck adding additional shielding but that may be due to my inabilty to fabricate a precision solution. Note there is an allowance for shields to be installed in the design that were not installed by the factory. Only one out of three possible shields were installed around the tuners. The only one that is present is between the two tuners (on my unit anyway).
I should have added this sooner but I thought I would wait awhile to see how reliable the fix was: Anyway I ended up tripling the value of the capacitor that is the power supply decoupling for the video output filter chip (as mentioned above). that has eliminated the problem and has remained a working solution since the time of the last update I did on this post (approx 8/1/2009). Also I only bothered to check this with a single composite video out connected. I have not checked it with s-video or any combination of multiple video outputs connected. I figured I would deal with that when and if I ever need it. But I imagine it will work as-is. Just to note I had a severe problem with even a single composite connected before this fix was applied.
I would guess the reason it starts off being a problem with s-video first and continues working for a while with composite is that s-video involves two signals being driven simultaneously(chroma, luma) and composite only involves one signal load at a time. Likewise explaining the reports of a single composite working but not both at the same time. A single signal at a time is the minimum load that can be placed on the output signal(s) via the filter chip circuit.
Also the way the board was designed to maximize scales of economy the output coupling capacitors for the two composite video lines are the same value as the decoupling capacitors for the video filter. So if you don't care about having composite video you can remove the two output coupling caps from the composite outs and connect them in parallel with the video filter decoupling cap and see if that allows the S-video to work. I obtained two new capacitors of that value to do my experiment and that's the way it is now (thus the tripling of the value). But removing the two composite output caps won't hurt anything other than not having the two composite outputs available. Of course figuring out where all this stuff is on the main board is half the fun. The other half is not blowing anything up. thanks for reading if you are still with me.
Would you be able to provide the reference designators on the PCB from where the capacitors could be removed and the location of where they would be placed to fix the s-video?
It probably only requires a buck or two in parts, but $100 for CCS to fix it was worth it, especially since I'm not an EE. Back up and running via S-video here. Not running 2nd tuner, but that's b/c there isn't a 2nd cable to the room.
Any updates on this?
Do we have anything that might resemble a "recipe" for this at this point? I have 2 tivos that are exhibiting this problem now. So far I understand that if I replace 1 cap on the power supply (possibly adding a second one where there's no capacitor -- I wasn't clear on how that helps) that may or may not do something.
Now it sounds possibly like the cap replacement on the power supply in conjunction with replacing some caps on the main board might eliminate the issue. I don't know my way around the main board well enough to know what which caps are which and what I should be replacing them with.
I'm eager to not have our shows randomly pixelating.
Yeah, I'd like a Dummies guide to fixing this problem. Does such a posting exist?
I don't think we are quite to that level yet. In lieu of a dummies version I will post the following below longer winded version of a procedure (better than nothing) and even though this forum probably doesn't appreciate such long winded posts.
Also note I don't know if this is what CSS does. I can't speak for them. But I will say that my fix does not address the root cause it is just a sort of stop gap. But it seems to work on the only other person's unit I know of that tried it so far with my direction. He is still giving it a thorough testing but initially said the worst pixellation on the most prominent channels that he noticed was gone. In my experience that is a very good sign and means in all probability there are no more pixellated channels on his unit. I thank that forum member for working with me to get this done to his HDVR2 with tuner 2 pixellation problems (including searching for signal on tuner2). It is possible CSS does a permanent and more correct fix that addresses the root cause. Even if I knew what they did I would not divulge it based on that knowledge. This is all based on my own experimentation and ideas. And of course credit goes to whomever noticed that removing a video output connection stopped the problem.
In response to requests to translate what I have stated as a cause of the problem and my solution into an easy (more or less) method of repair, I have some ideas now to present on the best way to install the modification for the least cost and trouble. Someone else can tell me if it can be made into a dummies version or not. To that end I have now tested a fix using a low cost part from a well known local electronics store that is found in many locations around the country that is stocked. The part is not a replacement for a part that has failed in the unit, but is to be added as a modification or enhancement of sorts. AFAIK it applies equally to all versions of the main board for HDVR2 that might exist. I say this not knowing if there are different hardware versions of the main board. Obviously you do this at your own risk and I do not accept any responsibility for any damage that might occur as a result. I have had it running in mine for several months and I don't anticipate any long term ill effects from the modification itself.
The part to be installed is a 470 uF 35V electrytic radial lead capacitor. There is nothing critical about the capacitor beyond its basic ratings (no low ESR, no low dissipation). It is a general purpose electrolytic capacitor. It should be rated to work with a regulated 5 volt DC power supply output as a minimum. (the 35 volt part meets that need).
The capacitor needs to be installed in parallel with C530 on the main board. C530 is the 220 uF smd electolytic that is on the end of the row of three identical capacitors not far from U49. Look at the silk screen numbers for a while in that area if you need to figure out which one is C530. There is a row of 4 capacitors beside these. Those may be either electrolytic SMD (like C530) or they may be tantalum SMD (smaller chip type and tan colored). Those latter four are audio output coupling capacitors and that locates all these parts near the A/V output jacks.
Part of the challenge is to figure out where to put the new capacitor and how to connect the leads to the circuit board. I have found two ways to connect it to the circuit that avoid interference with tuner 2 (the actual problem we are trying to fix). The first is to solder the leads to the solder pads of C530. The problem you encounter there is the pads do not extend very far beyond C530 plastic base where you could get to them. You can carefully nibble away part of the plastic to get the pads to be more exposed. Or you can use a soldering iron tip and melt the plastic a bit get it out of the way. It tends to shrink up. Observe polarity when connecting the capacitor. And watch out for shorts. All I can say is it can be done though it is not simple and removing C530 is even more difficult. The new capacitor should have the leads kept as short as possible and be positioned in the opposite direction of tuner2 (or away from the direction of the satellite inputs) to mimimze the possibility or interference with the tuner.
Another possible site to solder the capacitor is between pins 3 and 7 of U49 pin 3 is ground (-) and pin 7 is VCC (+). That presents it's own challenges because of the close lead pitch of U49 and the relatively large diameter of the leads to be soldered. Again keep the leads short and dressed away from tuner2. It won't look good but if it works, who cares? BTW U49 is the source of the interference that causes the pixellation - via the load placed on it by the video outputs.
I found the same ground and VCC at the site of the ommitted IC nearby (IC1or IC11 or whatever it is called). When I tried that location it interfered with tuner2 and the pixellation did not go away. An inch or even less makes a big difference it seems in relation to the interference issue. That site is too close to VR6 and tuner2.
Also I am assuming the basic problem is the ripple from load currents on U49 on this supply (VR6) and are what are interfering with tuner 2 and that is the true cause of the problem. That explains why this works of course. Although that concept also mutually involves tuner 2, this approach I describe might be a lot easier than trying to resolve issues with or around tuner2. Those issues might involve grounding of the chip and/or better shielding. I might look into that in time.
Also I did seem to notice that channels on Sat B and C (oval dish setup) might have more of a tendency to pixellate than those on A (101W) - although of course several (many?) 101w slot transponders are affected by this particular pixellation issue on this unit. Therefore if you try this and have a multisat setup and you know which of your channels come from the additional satellites, that you pay particular attention to those, since I could not test that setup thoroughly.
Please accept my gratitude for your above post...
My Hughes Dtivo had been having horrible pixellation on tuner 2. As you state it was mostly on the non 101 birds (it was especially bad on my locals which come from 119 I think). It was so bad that I considered tuner 2 dead.
I had tried switching out the hard drive. No joy. I was considering purchasing a new power supply (Which may actually fix the root cause?) but I do not have money for that. I was also considering sending the unit out for repair. But 1 or 2 weeks without DTivo??? Unacceptable...
I am not a professional when it comes to soldering. But I do have experience soldering leads to ICs (I have modded many devices in my household).
First I gathered my equipment... I have a pair of magnifying glasses that you wear like a baseball cap. They have 3 different levels of magnification and have small lights that you can turn on attached to the sides. I have had them for a long time. I purchased them from a local electronic supply house (not Radio Shack).
Next I have a 12w pencil soldering iron made by Weller that has a tip the size of an IC Lead. Again it was purchased at the local supply house. Radio Shack (RS) has one like this, but the tip is about 2 times as wide.
I purchased part 272-1030 from RS. It is $1.29.
Of the two places you mention to attach the new capacitor, the spot on the IC is a better choice. It has ample room on either side for making the attachment. The attachment spot on the capacitor has the issue of the plastic mounting in the way and on one side there is another row of capacitors which make attaching the lead there much more difficult.
I decided to lay the capacitor on its side with the leads extending over the IC, bending 90 degrees and attaching vertically to pins 3 and 7. Once I was happy with the placement, I fire up the soldering iron. I tinned the leads of the capacitor. I should have tinned the two IC legs (but I didnt). I was then able to use my offhand to hold the capacitor on the main board, and simply touch the soldering iron to the capacitor lead which was on top of the IC lead. A couple second later the solder had run and the first attachment was made. I repeated the process for the other capacitor lead and viola!
Once hooked back up I ran guided setup again and called DirecTV to reactivate my locals. I had to do this because I did a fresh install of the dtivo software on my drive. If you are just applying the mod, this will not be necessary.
24 hour results:
1) I have not seen the "Searching for Satellite on Tuner 2" message a single time. This is a huge improvement from pre mod.
2) I have not seen anything more than a momentary hiccup in picture quality.
Wether this mod lasts or not, I am happy I have done it. I no longer get the "OMG I cant watch Family Guy!!!" comments from my kids...
I was looking at soldering the cap across the IC. I would love to see some finished pics so I can see how you did it.
What do we thing the effects of long leads would be on the cap? Since it is in parallel, should it have as much effect as normal?
I wanted to leave feed back, I did this to a unit 2 days ago that had distortion on tuner 2 no matter what PSU I put in it. The test psu came from another hughes unit that did not display the issue. Same symptoms as many others posted, SVideo went first then composite afterwards. I used a 470 uf 25v (I had this on hand and 5V isn't enough to make 25-35v matter) over the IC pins 3 + 7.
The machine has been playing clearly for 2 days now.
I wonder if this indicates that VR6 is wearing or if there is a bad cap else where.
Dvrupgrade.com offers repairs on the series 2 units, including tuner repair. You can send them an email via their web site. They are generally quick to reply.
True but $0.13 cent capacitor from the pile of parts I have laying around is a bit better than $99 + shipping. Esp since I bought the thing for $45 shipped.
A big thanks to "schof" for those detailed posts.
I modded my Tivo over the weekend. Didn't have a 470 uF cap handy but used two 330's in parallel. A little extra capacitance can't hurt eh?
Ended up soldering directly to U49. See attached pics.
End result is that probably 95% of the pixelation and "Searching" messages have disappeared. Not perfect, but a huge improvement. The problem was always worst when watching 119 locals, and now I can actually tivo 2 locals at once again.
I have two units with bad video breaks ups. Put one of the 2200uf 16v caps left over from the power supply replacements caps on u49, and the units have not had any breaks ups since.
Thanks very much, for the post, it saved me may hours of troubleshooting.
Thanks, I just might try that, I still have a spare one myself.
I was initially pretty happy with the repair, but over the past few days it seems to be degrading back to where it was before. Not *as* bad, but lots of audio dropouts and still some pixelation.
Is there any way to do this with clips instead of soldering?
I installed the new cap over 2 weeks ago and everything still looks great.
It is a very tedious fix, but with some patience very doable.
Thanks for the help.
I'm a little confused by the postings so far. Is the capacitor that needs to be replaced on the main board or on the power supply?
I have pixelation on tuner 2, so after reading this thread I just swapped out the power supply from another device. It didn't help. I have two more units gathering dust in my closet, so I can certainly try a different power supply if that's a possible fix.
I am incapable of swapping out a capacitor myself, but my mom's husband is a TV repairman. I'm sure he could do it, but I'm not sure how to tell him what to do.
I have been following this thread and would like to know if the problem has been fixed? Have 2 Phillips 704 S2 with the problem. Anyone have an update on the repair after a few weeks of service?
My two HDVR2's have not had any video breakups, for over a month, since I added the cap on u49. They had very bad breakups before.