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Post by tibimakai on Oct 30, 2018 0:12:22 GMT -5
I have picked up this receiver, with shorted amp channel.
I'm also repairing another one, with no HDMI input(another thread on this forum).
What I have thought, is to replace the HDMI board and have a working receiver, but to my surprise, the receiver does not have any kind of output, no video(no menu either), and no audio either.
This receiver, looks like it's working otherwise. I have even made a firmware update.
Didn't measure anything yet. I'm thinking, that maybe the Q8000(MN864788) is bad?
I can't believe, how many HDMI issues are out here.
A blown audio channel, can take out an HDMI IC?
Any help would be appreciated.
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Post by tibimakai on Oct 30, 2018 23:32:21 GMT -5
At the HDMI ports pin #18, the 5V is missing.
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Post by tibimakai on Nov 9, 2018 1:10:26 GMT -5
I have repaired the amp. To my surprise, only the final transistors were blown. I never had an amp repair, that was so easy to repair. Maybe a car amp, a while back.
What I have noticed, that Q8000 is getting hot.
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Post by tibimakai on Nov 9, 2018 11:09:58 GMT -5
The only measurement I did last night, it was to check for short/voltage, at pin #36 of Q8302(HDMI SII IC). The 1.3V is there, but resistance is 293 Ohm. What that means? If it's shorted, the 1.3V shouldn't be there, right?
Not the SII IC is the cause this time, it is the MN Q8000, since is getting hot?
What should I check at Q8000? There are some weird voltage markings there, like 777_COM3. What should be that?
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Post by tjmotter on Nov 10, 2018 8:29:30 GMT -5
You are correct, since you have 1.3V, the chip is not shorted on the 1.3V line but that doesn't mean that it isn't shorting out the 5V line.
HDMI Receivers/Transmitters run on 3.3V (typically) but they must pass 5V through to the HDMI port to meet the spec. For some reason, this is often a weak point in the design and lack of 5V often means that one of the HDMI chips has blown. They often run hot so this isn't a huge concern. I would be suspicious of the SiI part only because you have a low resistance on the 1.3V line but Q8000 could be the culprit. The only thing I could suggest would be to remove one of them (probably the SiI) to see if the 5V turns on. If not, remove the second one (Q8000) to see if that is the culprit.
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Post by tibimakai on Nov 15, 2018 11:39:37 GMT -5
I have a question about this "short". When the board is mounted into the receiver, I measure 293 Ohm. If I remove the board, there is no short. I have noticed, that if I connect the HDMI connectors to the metal back cover, than when the "short" shows up.
It is still considered short, and I should remove the IC?
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Post by tjmotter on Nov 15, 2018 12:16:44 GMT -5
I would suspect so. The 5V signal is only used for HDMI handshaking (no processing at all) so if it shows a short when connected to an HDMI cable, it would seem to indicate that the 1.3V signal is shorted to the 5V signal. You can test this by using your meter to read the resistance between the 5V rail and the 1.3V rail. It should be very high. If it measures a short, it would indicate that the HDMI chip has an internal short between these two rails.
HTH
Todd
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Post by tibimakai on Nov 17, 2018 21:54:34 GMT -5
I have removed the SII IC(Q8302), but the 5V did not show up. Q8000 (MN IC) is getting too hot.
At some pin #18s, I measure 0.23V, 0.007V, 1.3V, etc.
Should I remove now, Q8000?
I have another question about the amp.
There is a need, to even check the idle current? The connectors are there, but there is no adjustment for them.
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Post by tibimakai on Nov 18, 2018 0:57:12 GMT -5
I have bolted down all the HDMI connectors, just in case if that matters. Only on the outputs I'm getting 0.23V, at pin #18.
0v, at all of the inputs.
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Post by tibimakai on Nov 18, 2018 17:25:40 GMT -5
If I remove Q8000, the 5V at the HDMI port should show up, or it will show up only, when a new IC is soldered in?
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Post by tjmotter on Nov 19, 2018 18:15:14 GMT -5
The 5V comes from the HDMI Receiver chip so you won't see voltages at the ports until the chip is replaced
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Post by tibimakai on Dec 8, 2018 3:13:28 GMT -5
OK, I have replaced both HDMI chips and there is still no audio or video from an HDMI source. There is no 5V at pin #18 at the HDMI ports. At the two outputs I measure 0.27V , but at the rest, only 0.019V.
At least, none of the HDMI chips are getting hot.
What else could I do next?
If I pair my phone via Bluetooth, the audio works great.
If I hold the Display for a couple of seconds, it will show Unknown and than ----. With the Directv box plugged in and turned on. Also the TV is plugged in and turned on.
No HDMI sign, shows up on the display.
Any help would be appreciated.
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Post by mastertech on Dec 8, 2018 10:53:53 GMT -5
I do not believe the HDMI in's should have voltage on the 5v line. Those are detect lines which would indicate the device connected to it should be putting out 5v.
The HDMI out's should have 5v and according to your schematic that 5v also supplies the data and clock lines for HDMI. So it appears as though your +5VTX line is down.
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Post by tibimakai on Dec 8, 2018 19:34:48 GMT -5
I will go over my soldering job, just to be sure. The SII IC came out really nice, but the MN IC is not the nicest.
But if it's not the soldering, than what else could be the problem?
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Post by mastertech on Dec 8, 2018 20:09:59 GMT -5
Not sure why you are thinking there. The +5VTX comes from Q8151. You need to test voltage at pins 1,3,5. Use pin 2 for gnd.  |
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