nashou
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Post by nashou on Mar 20, 2017 20:43:43 GMT -5
False alarm. It's fine I retested it on the tester.
Sorry
Back to normal scheduled programming.
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Post by mastertech on Mar 20, 2017 20:50:38 GMT -5
Ok, recheck the 2 ic's vcc.
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nashou
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Post by nashou on Mar 20, 2017 21:40:22 GMT -5
Ok, recheck the 2 ic's vcc. No Change same as before. Nashou |
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Post by mastertech on Mar 20, 2017 21:53:09 GMT -5
Same, meaning 5v on 1 and 4.5v on the other?
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nashou
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Post by nashou on Mar 20, 2017 22:45:44 GMT -5
Yes
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Post by mastertech on Mar 21, 2017 10:04:32 GMT -5
I want you to do an ohm test between ic902, pin 8 (vcc) and ic901, pin 12 (vcc). Naturally do not plug it in.
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nashou
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Tech in Training.....
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Post by nashou on Mar 21, 2017 10:33:58 GMT -5
I want you to do an ohm test between ic902, pin 8 (vcc) and ic901, pin 12 (vcc). Naturally do not plug it in. 158kohm !!!! It should be zero right? |
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Post by mastertech on Mar 21, 2017 10:37:41 GMT -5
Yes. Check the trace for damage, going to the ic with the lesser voltage.
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nashou
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Post by nashou on Mar 21, 2017 11:06:49 GMT -5
can't see any but I noticed my Board layout is different than the one in the SM. My version is 715T3150-3 the SM has the last digit as -1 . Where J921 is on the layout my board has D933 which is not in the SM we have, also it happens if i do an ohm reading across that diode it is exactly the same as from the two vcc pins. If you follow the layout traces J921 ( my board d933) goes right to pin 8 on ic 902 via J919. So they lowered the voltage with that diode for some reason. Nashou FULL SIZE IMAGE link !!!! www.flickr.com/photos/21885221@N04/33443343351/sizes/o/ |
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Post by mastertech on Mar 21, 2017 11:13:47 GMT -5
Ok, good to know. Now we can continue.
I want you to locate RV903. Remove it and then test the DC voltage at BD901, pins 1 and 4 and see what the voltage is now.
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nashou
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Post by nashou on Mar 21, 2017 11:22:05 GMT -5
No RV903 that I can find. , I have RV 902,904 and 905. the three yellow round discs.  |
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nashou
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Tech in Training.....
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Post by nashou on Mar 21, 2017 11:30:01 GMT -5
It's not populated.
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Post by mastertech on Mar 21, 2017 11:58:40 GMT -5
Well we need to see why that voltage is low. Guess you will have to remove some parts, 1 at a time and see if that voltage at BD901 comes up to the 300 to 400 volt.
Looks like you need to remove Q902, C929, D903. Test BD901 after each removal so we can see a direction if it changes.
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nashou
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Post by nashou on Mar 21, 2017 13:37:45 GMT -5
Pulled all three no change.
Off to work , be back after 9pm
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Post by mastertech on Mar 21, 2017 14:28:51 GMT -5
Ok, when you get back to it I want you to remove BD901 and set your DMM on diode scale and test it carefully. Have you ever tested a bridge rectifier before?
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