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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Oct 23, 2012 3:08 pm Post subject: |
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| barclay66 wrote: |
Usually You would expect some kind of control via I2C coming from an system controller (IC701, Main CPU). On this schematic this doesn't happen. IC701 only controls SDA0/SCL0 and SDA1/SCL1. I'ts not clear to me where control over SDA2/SCL2 comes from.
Regards,
barclay66 |
Right, IC701 (MCU) does not control this bus line. But it does control the ATSC by way of transmit and receive lines (RX TX) and the ATSC has a controller that then handles the bus line in question.
As you can see, we are finding things out and we haven't even picked up a test meter yet or taken anything apart. Fun, yes?
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Tue Oct 23, 2012 3:13 pm Post subject: |
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Funny, this is the area of repairs that I'm really weak in. Learning lots here.
My guess is that since multiple symptoms are common to this one problem, it seems like it's almost an issue as with IC421 in the G90s. Loss of I2C lines, and you have all sorts of random stuff happening.
Leaky cap or open resistor on the line?
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Tue Oct 23, 2012 3:13 pm Post subject: |
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| macgyver655 wrote: | | As you can see, we are finding things out and we haven't even picked up a test meter yet or taken anything apart. Fun, yes? |
Yes, but at this point I would...
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Tue Oct 23, 2012 3:15 pm Post subject: |
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| Curt Palme wrote: | | Leaky cap or open resistor on the line? |
Or one of the devices randomly screwing up the bus.
This could well be IC801 as component input never works. Maybe the diagnosis can be done with one finger only: If this IC gets hot shortly after powering up it most likely will be the culprit...
Last edited by barclay66 on Tue Oct 23, 2012 3:25 pm; edited 1 time in total
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Tue Oct 23, 2012 3:23 pm Post subject: |
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It's the intermittent part that's throwing me off. USUALLY, parts aren't intermittent. Maybe a cracked SMT solder joint rather than a failed part?
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Tue Oct 23, 2012 3:27 pm Post subject: |
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| Curt Palme wrote: | | It's the intermittent part that's throwing me off. USUALLY, parts aren't intermittent. Maybe a cracked SMT solder joint rather than a failed part? |
Well: Intermittent may not be the correct term. Please bear in mind that English isn't my mother language. Please see my edited post above. Lets call it a thermal problem...
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Oct 23, 2012 3:33 pm Post subject: |
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| Curt Palme wrote: | | It's the intermittent part that's throwing me off. USUALLY, parts aren't intermittent. Maybe a cracked SMT solder joint rather than a failed part? |
Yes, it was bugging me also. So it was then more of trying to determine if it was in the ATSC or not first.
Barclay: I've noted your suggestions but I wanted to get some more responses and suggestions on where to proceed with testing. So lets assume the 3.3v supply is ok.
I have to run out for a few hours so I'll respond when I get back.
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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| Posted: Tue Oct 23, 2012 3:54 pm Post subject: |
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I say it's more a problem with the SDA2 signal over the SCL2 just because the SDA2 is a two way signal. Not sure how the OSD communicates with the AV select but lets say the signal from SDA2 gets to the OSD to make the change but then it does not get back to the AV select to make the actual input change. So something is blocking the SDA2 signal from going in both directions.
Nashou
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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| Posted: Tue Oct 23, 2012 4:00 pm Post subject: |
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to go further, in macs first post he states that the Component doesn't seam to work at all and it always go back to ATSC tuner just no sound. So this would say to me that the input change to Input 1 or 2 ( component) never gets made but its audio does. This is why there is no audio on the tuner after selecting the component input, the audio would get redirected but the video stays to ATSC. this is also why in a later post mac says he is finding audio on the Pre amp outs as they would got here no matter which input is selected.
Nashou
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Oct 24, 2012 12:06 am Post subject: |
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So lets see where we are at. We now know we have a problem with ic251, ic801, ic621 and/or the ATSC tuner which is the controller.
As usual the first thing I would suggest is to check supply voltages to these chips as they may be all powered from the same source. However, ic621 and ic251 are 9v supply and ic801 is 5v supply. Of course the 5v supply could be from the 9v supply through a regulator. But, if we look at ic641 which is for fixed audio out, which we do have even when it's acting up, it uses the same 9v supply, so it can't be a supply voltage problem. So we can rule that out. Did you follow that? LOL
Now ic701 is the main cpu and communicates with the ATSC controller but channel changes and audio and video coming out of the ATSC are fine so I would not think it's a problem there.
So it has to be related to the I2C bus line, since that line ONLY controls the 3 ic's we are having trouble with.
So my first thought was to check the 2 mosfets in the control lines (Q001 and Q002) and their supply power. Fortunately they were right on top of the main board and easy access. None of the legs showed any shorts between themselves, to each other or to ground. I then checked both the 3.3v and 5v supply voltages and they were fine.
So now what are you thinking?
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Nashou66
Joined: 12 Jan 2007
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Oct 24, 2012 4:36 pm Post subject: |
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| Nashou66 wrote: | Are D251 and D252 working ok?
Athanasios |
If you look closely at the print you will see it says "open" for those 2 diodes. So they are not there, which they are not.
Looks like interest in this thread is lost so I'll just let it go.
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gjaky
Joined: 05 Jun 2010
Posts: 2802
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ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
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| Posted: Wed Oct 24, 2012 5:08 pm Post subject: |
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No, Mac... Interest not lost at all... Some of us are just learning by lurking because we have nothing intelligent to add, and others have busy lives and may have to go a day before posting anything - both. 
Please continue.
SC
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Nashou66
Joined: 12 Jan 2007
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Oct 24, 2012 7:19 pm Post subject: |
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Ha, just checking to see if you guys are still awake.
Even if you don't have anything intelligent to add you are more then welcome to ask questions. The point of the exercise is to learn. Maybe I should of titled the thread "Some fun for all you guys"....
At this stage I was curious as to which direction some of you guys would take. I know what I would do, which is what I did, but still curious and as to why. I've seen many techs go in the completely wrong direction (my opinion) and couldn't figure out why. Unless they were just hunting. Now sometimes you do need to hunt, but I consider that a last resort.
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Wed Oct 24, 2012 8:32 pm Post subject: |
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ok, Im just going to say it...
CAPACITORS!!!
I would like to be right by just randomly guessing like that anyway  It sure sounds like a capacitance related issue, causing random issues, such as capacitors love to do when they start breaking down.
Am I even close?
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Wed Oct 24, 2012 8:43 pm Post subject: |
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Is the Clock signal present and stable at all affected ic's input?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Thu Oct 25, 2012 12:30 am Post subject: |
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| gjaky wrote: | | Is the Clock signal present and stable at all affected ic's input? |
I see your point gjaky and I don't disagree. But I always try to keep my trouble shooting simple. I guess my thinking is sometimes not the norm but it generally seems to work in my favor.
So I guess it's time to close this repair.
We left off with having come to the conclusion that the problem has been narrowed down to the controller or 3 controlled ic's.
Now we don't have the schematics for the ATSC to trace in that direction but we can conclude a few things about it. we can conclude that the bus lines that enter the ATSC probably go directly to the controller ic. So if the problem is in the ATSC then this ic would have to be replaced.
How can we be so sure there are no other ic's in the ATSC being controlled by the I2C bus? Because of the placement of the 2 mosfets (Q001 and Q002). The controlling side of the mosfets, the drain pin (D) would have to reenter the ATSC. They don't, only the source pin(S) does and it can't control more ic's from that side. So there's not much to be tested or looked at in there.
So at this point we just need to determine if there is a problem with the 3 slave ic's. So my next thought was to try disconnecting 2 of the 3 ic's bus lines and see if the remaining one would come to life. I chose the sound chip to remain because it's easier to verify. I was going to disconnect the other 2 chips by removing 4 resistors (r270, r271, r803 and r804). this would then leave only ic621 connected to the bus line. See, simple.
Now comes the funny part!
In order to remove these resistors I needed to remove the main board from the tv and put it on the bench. Removal was very easy, only a half dozen harness connections and some plastic clips. no screws.
So I put it on the bench and I'm looking at the board and near the back edge there was an open area about 2.5 inches by 1.5 inches where there were no components, just traces. And what do I see there but dried mouse pee. I knew it was mouse pee because there were also some droppings. Ah ha I thought. The pee is conducting across some traces and causing the malfunction. So I get the electronic board wash and a tooth brush and clean both sides of the board and let it dry.
I then reinstall the board thinking all will be well and turn it on. I have tuner picture but no sound. Try the inputs and nothing. Hmmm, now even cold I have nothing. So although I have the same symptoms they are there right from the start so it is different. So out comes the main again and it's time to do some continuity testing.
Dmm in continuity with tone set on (easier to listen then keep looking). Using the mosfets as the starting point I test from each D pin to the 3 ic's control pins. All is well there. I dont need to test the mosfets Gate(G) pins because we tested for voltage there in the beginning and voltage was present so those lines are fine. So we need to test the 2 S pins to the ATSC socket. So I remove the ATSC tuner (it just unplugs). Q002 S pin to pin 7 on the socket, beep. Q001 S pin to pin 44 on socket, no beep. Ah ha again, lol.
So I follow the trace from Q001, S to a point on the board where the trace passes through the board to the other side. It's like a tiny hole in the board where the trace would pass through to the other side. So I check for beep from S pin to trace hole and have a beep. I flip the board over and test from hole to pin 44 on the connector, I have beep. I test from hole on 1 side to hole on other side, no beep.
So the mouse pee seeped into the trace hole and burned the trace open. So apparently when the tv was cold the pee would conduct the signal enough for the data signal to work. And as the pee warmed up (yuk) it would loose conductance and then no data control. And then washing the pee off I lost all conductance.
So I soldered a very thin, insulated wire from the S pin of Q001 to the mounting pin of pin 44 of the ATSC.
Put it back together and all functions are fine, including the component inputs.
So no peeing on your electronics.....
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Nashou66
Joined: 12 Jan 2007
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Location: West Seneca NY
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