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Post by mastertech on Mar 6, 2017 20:03:30 GMT -5
They are surge protection devices. Like MOV's. Sometimes when there is a big surge and they try to conduct the surge away, they go short. Then it is a direct short on the circuit.
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nashou
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Post by nashou on Mar 6, 2017 20:12:00 GMT -5
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Post by mastertech on Mar 6, 2017 20:14:19 GMT -5
Your links do not work.
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nashou
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Post by nashou on Mar 6, 2017 20:16:33 GMT -5
I just checked on another computer and they did? Nashou |
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nashou
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Post by nashou on Mar 6, 2017 20:19:45 GMT -5
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nashou
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Post by nashou on Mar 6, 2017 20:38:33 GMT -5
The Varistors measured OL . So those are good but I did find one had a loose solder joint. it was wiggling in the hole( RV904) I wonder if that could have caused the failure?
EDIT: ic902 I con not find at digikey its a SG6961 . Not sure if its bad, How would I test it? And if it is bad and I put other parts in would it risk those blowing too?
Nashou
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Post by mastertech on Mar 6, 2017 20:45:56 GMT -5
I do not see an advantage of 1 ST over the other so your choice.
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Post by mastertech on Mar 6, 2017 20:49:54 GMT -5
What style SG6961? DIP or SOP?
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nashou
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Post by nashou on Mar 6, 2017 20:53:28 GMT -5
SOP, Mouser has them but for the one part it be 8 shipping and I ordered the other parts at Digikey.
Nashou
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Post by mastertech on Mar 6, 2017 20:58:16 GMT -5
Welcome to the wonderful world of electronics repair.  |
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nashou
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Post by nashou on Mar 6, 2017 21:00:30 GMT -5
Think it be wise to order it , or just hope it's not blown . It was one of the parts listed in the trouble shooting section.
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Post by mastertech on Mar 6, 2017 21:04:06 GMT -5
Well it is the driver for the mosfet that was bad, and it is common for it to fail when a mosfet blows. Are you sure the shipping is that much. Ask them to just put it in an envelope. I have done that before.
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nashou
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Post by nashou on Mar 7, 2017 12:24:04 GMT -5
Found some more resistors burnt. SMD R983 10 ohm read open. Have various 603 and 805 packaged resistors. Also R932 330 ohm was burnt. This is under the large coil L903. How should I test that coil? I had to remove it to replace R932. This are all surrounding ic902 . Maybe the resistors blowing protected that ic?  Mouser also said they don't put parts in envelopes so they did offer a cheaper shipping not listed on their online. between 2-5 dollars . so I ordered 4 pieces . Nashou |
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nashou
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Post by nashou on Mar 11, 2017 17:01:01 GMT -5
Installed all the new parts. Should I do the jumper again to see if I get the correct voltages?
One thing, I kept the hot air too long on ic902 when removing it and the board bubbled up a bit. Delaminated. I checked all continuity points from the legs of that IC and some surrounding parts to make sure its ok.
Seems like no harm was done. And I don't think any through holes or bias are in that section. except for the ones in the pic above. Those are ok.
Nashou
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nashou
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Post by nashou on Mar 11, 2017 18:20:04 GMT -5
Well still nothing, but at least no parts blew . I think maybe one or more of the optocoupler phototransistors TCET1103G might be bad.
There are three on the board all have readings between pin 1 and 2 in both direction and for pins 3 and 4 but ic909 measures as a diode would on 1 and 2 and for 3 and 4 its OL but for a short time it has a reading on one direction, I think its from me testing pins 1 and 2 and It activates the
LED ? they are ic 909,910 and 911.
How do I test theses? I might try my tester but not sure it it has those types of parts programed into it.
nashou
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