nashou
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Post by nashou on Mar 23, 2017 19:59:19 GMT -5
Ok, now after R970 then after R971. Then value test R991. 49, 1.046 and R991 was 47 ohms as should be. it seems like voltage was dividing by two till after R971 ? |
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Post by mastertech on Mar 23, 2017 20:27:53 GMT -5
Does R971 value test correctly?
Remove D908 and see if you still have 5v at connector CN902.
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nashou
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Post by nashou on Mar 23, 2017 20:53:15 GMT -5
I believe its fine. My DMM takes a long to read those three resistors. And one direction it starts low then rises and in the other direction it starts way higher and drops. but my LCR meter with
a built in test tone of 120hz 1 kHz and 120hz reads it at about 650kohm to 700khm, it bounces around.
the 5 volt is there with D908 removed.
nashou
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Post by mastertech on Mar 23, 2017 21:01:15 GMT -5
Ok, that reduction to 1 volt is fine.
With D908 removed I want you to do an ohm test across that transformer, pins 4 and 5. Let me know.
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nashou
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Post by nashou on Mar 23, 2017 21:04:30 GMT -5
.2 ohm
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Post by mastertech on Mar 23, 2017 21:18:36 GMT -5
Ok,here is where we are. I have been chatting with some others who are more in the engineering area and it has been confirmed that the switching of Q902 is whats boosts that DC voltage to 400vdc. But this voltage should only show up after the coil and maybe even after D903. So we need to test after here just in case. Now based on some other tests I had you do, Q902 is not running and neither is ic902. So this is why we do not have the 400vdc. So why is it not running. Well I did some more research and it looks like ic902 needs at least 12vdc on vcc to turn on. And we only have 5vdc. So this may be the problem which is why I have you back in the area of ic903 which is where this voltage is created.
Now rather then keep on guessing I would like to try powering these ic's with 12vdc and see if it comes to life. You can use your external power supply for the 12vdc.
I will write up the procedure in the next post which I am doing now. So get your external supply ready and set it for 12vdc output.
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Post by mastertech on Mar 23, 2017 21:24:59 GMT -5
Leave D908 out for now. Take R976 and position it so it is still connected to the pad which goes to Q922. Then connect the other side of it to your external PS pos lead. Connect the neg PS lead to hot gnd. Now do not plug in the Sharp PS yet. Turn on your external supply and test the voltage at ic902, pin 8 (vcc) and ic901, pin 12 (vcc). I am looking for 12vdc on ic902 and app. 10.7vdc on ic901.
Let me know when you are here.
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Post by mastertech on Mar 23, 2017 21:33:19 GMT -5
I just realized you wont have your vcc voltage with the sharp PS not plugged in. So I want you to jump pins 1 and 3 of Q922 with some solder just for this test. You can leave the transistor mounted if possible.
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nashou
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Post by nashou on Mar 23, 2017 21:40:37 GMT -5
No luck , but the voltage is on on Q922 emitter and base not on the collector . I guess due to the fact that the opto is not working with no voltage to it .
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Post by mastertech on Mar 23, 2017 21:44:38 GMT -5
See post above your last.
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nashou
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Post by nashou on Mar 23, 2017 21:56:12 GMT -5
Ok, icl902 12,
Ic901 11.47
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Post by mastertech on Mar 23, 2017 22:00:08 GMT -5
ic901 is a smidge high. Drop it to 11.3 and see what ic902 ends up at.
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nashou
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Post by nashou on Mar 23, 2017 22:04:08 GMT -5
It ends up at 11.98
No other voltages on other pins especially pin 7 the driver voltage.
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Post by mastertech on Mar 23, 2017 22:05:48 GMT -5
Now shut off your supply and remove the solder on Q922 so it is mounted normal. Then take your DMM on DC and connect the pos lead somewhere after D903 to monitor the 400vdc line. Connect neg lead to hot gnd. and leave your meter on. Have the standby jumped to the 5v. Turn on your external supply then plug in the Sharp supply. Have your safety glasses on. See what your line voltage is now.
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nashou
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Post by nashou on Mar 23, 2017 22:17:09 GMT -5
Ok, where after d903? I tried fb903 and got 166
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