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Post by tibimakai on Nov 6, 2018 23:11:34 GMT -5
I have just noticed that you have wrote about the final transistors. Yes I'm buying them from Digikey. No transistors from China, only the ICs that I can't find here. I'm using the 2SA1962/2SC5242 once.
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Post by tibimakai on Nov 7, 2018 0:27:06 GMT -5
I'm having a hard time measuring these transistors. Not all measure the same.
Q7005 measures 2.5V between Base and Emitter, and OL between Base and Collector.
If I reverse the test leads, I measure 3V, between Base and Emitter. I'm measuring, only the bottom row transistors right now.
Only Q7019 does show OL between Base and Emitter. This is the only good transistor, and the others are all shorted?
I have to measure the two row transistors under Q7009, right?
These are: Q7002, Q7005, Q7003, Q7007, Q7004, Q7006, Q7021, Q7023, Q7008, Q7019, Q7000 and Q7010, right?
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Post by tibimakai on Nov 7, 2018 21:16:09 GMT -5
I have measured Iprotect and Vprotect diodes, and none of them is going high.
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Post by tibimakai on Nov 13, 2018 15:04:50 GMT -5
There is anything else, that we could do?
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Post by tjmotter on Nov 14, 2018 9:49:27 GMT -5
First, I would try to install that 2nd MPU I sent you. I put a newer rev of software on it so we may see a different result. Second, I would recommend that you ship the RZ800 MPU to me along with the one you pull off. I will try to clean it up and see if I can get the sw image off of it.
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Post by tibimakai on Nov 14, 2018 11:30:11 GMT -5
Do you think, that it could make a big difference, with the other MPU?
Which one should I send to you, the one that is soldered in now and the original one?
I was wondering, how could I know, if those transistors that I have replaced, they are all working OK, and there are no more faults coming from there?
Maybe I have missed something, or who knows what else could be damaged?
It is hard to believe, that the MPU software could be that much different from a 838.
How can we rule out, any other error(s), that may be still lingering in this receiver?
I would rather look into these, before I would pull off the MPU.
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Post by tjmotter on Nov 14, 2018 15:52:45 GMT -5
The software image is a big deal. It determines how the entire Receiver is configured.
I would want the one that is soldered in now and the original one.
The Mute transistors don't emit a fault, they merely shunt the audio signal to ground so it shouldn't impact the Main CPU.
There are probably additional errors. The only mechanism I know of is to address them one at a time. Feel free to keep checking and reach out to me if you want to proceed with the CPU change.
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Post by tibimakai on Nov 14, 2018 21:47:10 GMT -5
What you are trying to do, is to read the original MPU and transfer that software, to the 838 MPU?
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Post by tibimakai on Nov 15, 2018 1:46:54 GMT -5
OK, I have replaced the MPU, and now acts completely different.
No display at all, I can hear a couple of relay clicks, I believe three times.
I felt warming from the pre-amp area, some smoke odor.
I have started measuring the four big coils on the HDMI board, and all voltages were correct.
Reset the unit, with CBL and ON/Stby. It seemed like, is doing what it suppose to do.
After that started smoking, from somewhere way down near the two big filtering capacitors.
Can't see, from where actually the smoke comes from.
Why would smoke? Most likely there is still something wrong with it.
Definitely it comes from the mainboard, or the one, which has the mute transistors.
Wrong software could cause the smoke?
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Post by tjmotter on Nov 15, 2018 8:29:02 GMT -5
Wrong software would not cause smoke. You have a hard fault somewhere in this area that will need to be addressed. It could be one of the voltage rectifiers has gone bad.
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Post by tjmotter on Nov 18, 2018 7:44:32 GMT -5
The smoke could also be coming from the Volume chip. I really hope not because that is one of the hardest chips to replace but you should check it for shorts.
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Post by tibimakai on Nov 18, 2018 13:46:48 GMT -5
What should I check, positive to ground?
It was a slow forming smoke. Not an instant one.
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Post by tibimakai on Nov 18, 2018 16:47:24 GMT -5
I have paused with this receiver for a bit.
I'm concentrating on the 646s, with the HDMI ICs.
One is repaired, but I still have issue, with the other one.
Than I will go back to the 838, that smokes. I haven't mentioned this here, only at Badcaps forum.
Everything looks good, but it still smokes out a 2.2 Ohm emitter resistor, for a TTA pre-amp transistor.
When I have these repaired, or waiting for the MN IC, I will be back to take this 800 appart.
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Post by tibimakai on Nov 19, 2018 21:55:34 GMT -5
I have just taken apart the receiver, and I see R4905 burned(PCB bubbled up below it) Most likely, R4906 is burned as well.
It is pretty much, the 12 to 7V power supply. I will test the transistors and Q4001, Pin #91-92 for short.
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Post by tibimakai on Nov 19, 2018 23:03:46 GMT -5
As bad as it looks, chard resistors they still show their proper value(22 Ohm both of them), which is interesting. Transistors Q4901-Q4902 show .5-.6V each way, which is not OK, but out of the circuit, they look OK. SMD transistors Q4903-Q4904 show OK, after I have removed the other two transistors. What I have noticed, is the Q4142 has a bulge in the middle. Q4001 pin #91 and #92 do not show short, ~250 KOhm. It seems like this IC is not shorted, right?   |
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