Deleted
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Post by Deleted on Sept 27, 2015 23:12:04 GMT -5
I think you will have problem with smd small resistor.
I think you can also cross the feedback signal at the big resistors R20 and R21 to R80 and R81 and also cros CVL B with CVL R so the low side of the coil?
Please wait for confirmation of Mastertech. But this way you can work with the 2 watt big resistors.
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Deleted
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Post by Deleted on Sept 27, 2015 23:53:37 GMT -5
Or R78 R79 with R18 R19 might be simpler?
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Post by mastertech on Sept 28, 2015 0:04:40 GMT -5
I think you will have problem with smd small resistor. I think you can also cross the feedback signal at the big resistors R20 and R21 to R80 and R81 and also cros CVL B with CVL R so the low side of the coil? Please wait for confirmation of Mastertech. But this way you can work with the 2 watt big resistors. I don't think you are quite seeing what is trying to be accomplished here. Keep looking at it and maybe it will come to you. But the answer is: it must be R4 and R64. It is really starting to look like decibel is not capable of this type of testing. I have no problem assisting anyone by saying, do this and this and tell me what you get. But when there is difficulty and re-questioning every time I give a procedure then I have no interest in continuing. Plus it appears to just create more problems. So I am most likely going to end my assistance here. Decibel, you might as well put it back to how it was and either get another board or have it repaired by someone else. |
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Post by Decibel on Sept 28, 2015 0:22:01 GMT -5
I have a hot air solder station.
So I have no problem to operate with SMD components.
The difficulties that I have are the PCB of these units, really very fragile and the understanding the language.
Then also the points of check of the resistors.
The crossing circuit of transistors is ready. Today I will make the crossing circuit of resistors.
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Post by Deleted on Sept 28, 2015 3:32:43 GMT -5
Ok. Be carefull with hot air. It is easy to blow all parts of a board away. Personally I like using desolder wick with smd. Both sides and than take off. I also have a magnefying light.
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Post by Decibel on Sept 28, 2015 10:18:30 GMT -5
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Post by Decibel on Sept 28, 2015 10:31:30 GMT -5
  this is microsurgery |
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Post by Decibel on Sept 28, 2015 10:41:46 GMT -5
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Post by Decibel on Sept 28, 2015 10:53:06 GMT -5
The issue shift to blue   |
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Post by mastertech on Sept 28, 2015 14:35:35 GMT -5
Very good. So what do you think this tells us?
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Post by Decibel on Sept 28, 2015 14:43:36 GMT -5
Very good. So what do you think this tells us? I don't know. Perhaps there's something before these components that's broken. I90? |
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Post by mastertech on Sept 28, 2015 15:46:44 GMT -5
Very good. Yes, something before where we tapped in is most likely at fault. To be specific, something in the red square in the attached image. Now you just have to narrow down further. I would first check for the correct voltages right on the pins of I1, pins 4 and 7 (See yellow circles). Even though the voltage rails are surely ok cause the other channels work, there could be a break in the trace to this ic. If the voltages check ok then I would value test all the resistors in that red square, then test the 1 diode and then the 1 transistor. You should remove the diode and transistor for testing because they may have just very minor leakage which can be undetectable in circuit. If all tests are ok then I would just test the caps for short. Value should not be critical, at least not yet. If no shorts then I would just change I1 and I90 if they are cheap. And if they are cheap. I would order a couple in case of error during replacement. Let me know how you make out. Oh, and leave those jumper in place for know. Do not return it to normal. We will be testing for the blue channel to become normal for now.  |
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Post by Decibel on Sept 28, 2015 17:27:52 GMT -5
For my memory, the components of red square are ...
R1 4K7
R2 2K4
R3 1K3
R4 4K7
R5 3K3
R6 1K2
R7 10E
R8 1K
R9 1K2
R90 1K8
R23 1K
C1 100n
C2 100n
C3 150p
C5 680p
C7 680p
C8 100n
Q1 BF470
Z2 8,2V
I1 NE5534
I90 DG445DY
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Post by mastertech on Sept 28, 2015 20:15:46 GMT -5
Yep
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Post by Decibel on Sept 29, 2015 2:56:32 GMT -5
For my memory, the components of red square are ... R1 4K7 R2 2K4 R3 1K3 R4 4K7 R5 3K3 R6 1K2 R7 10E R8 1K R9 1K2 R90 1K8 R23 1K C1 100n C2 100n C3 150p C5 680p C7 680p C8 100n Q1 BF470 Z2 8,2V I1 NE5534 I90 DG445DY I will check voltages this evening. I checked values of resistors and there's a strange value of R2* labeled 2401. Below all values checked. Meter at 20k except R7 (meter at 200). R1 4.66 k R2 0.87 k (*) R3 1.30 k R4 4.70 k R5 3.28 k R6 1.20 k R7 115 ohms R8 1.01k R9 1.20 k R90 1.44 k R23 1.04 k |
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