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Post by mastertech on Feb 27, 2015 22:51:50 GMT -5
Conversely when I tested from the raised end of the diode I got a reading of around .965 on cap scale. Also, I assume you mean diode scale? |
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Post by justgreg on Feb 27, 2015 23:32:24 GMT -5
Yup...understood about testing caps in situ. I have a Blue ESR but I was just killing some time testing across caps. Before you posted I had time to think about what I was doing. It was a flawed assumption on my part thinking that I could point my finger at a cap that tested shorted across because it dawned on me that we're trying to find a short on the power rail, so of course a cap could show a short on both sides when tested in-circuit. Live and learn.
I'll post a pic of the backside of the area you marked and post it tomorrow. Damn flu has me whooped.
Thanks again for your help so far Mac!
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Post by mastertech on Feb 27, 2015 23:35:50 GMT -5
Your welcome. Happy to assist.  |
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Post by justgreg on Feb 28, 2015 14:29:19 GMT -5
Just re-reading. Yes I meant diode scale. Here's the backside under the diode showing the 4 holes. Camera will take good macros one time and be crap the next. I hope this is the detail you wanted.  |
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Post by justgreg on Feb 28, 2015 15:25:05 GMT -5
What are your thoughts on:
*Temporaryily bridging/replacing the lifted diode with a resistor (suggestion for the value?)
*Applying 1.5vdc input at the mains in
*Using freeze spray to identify hot components
The lowest voltage TP I found was 1.8v. The variable voltage wall wart I have (RatShack) only goes as low as 1.5v but I can add a resistor in-line. (suggestions for a value?)
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Post by mastertech on Feb 28, 2015 18:48:40 GMT -5
What are your thoughts on: *Temporaryily bridging/replacing the lifted diode with a resistor (suggestion for the value?) Absolutely not.*Applying 1.5vdc input at the mains in Do not see the point.*Using freeze spray to identify hot components Again, no point in this scenario.The lowest voltage TP I found was 1.8v. The variable voltage wall wart I have (RatShack) only goes as low as 1.5v but I can add a resistor in-line. (suggestions for a value?) |
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Post by mastertech on Feb 28, 2015 18:52:38 GMT -5
Do the diode test on the 2 lower right pins of that regulator and give me the readings. Do probes both ways.
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Post by justgreg on Feb 28, 2015 19:52:01 GMT -5
.979 = Red on pin 1
.491 = Red on pin 2
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Post by mastertech on Feb 28, 2015 22:03:39 GMT -5
.979 = Red on pin 1 .491 = Red on pin 2 And the black(neg) probe was on the opposing pin when you did this? |
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Post by justgreg on Feb 28, 2015 22:16:52 GMT -5
Yessir. Reversed probes.
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Post by mastertech on Feb 28, 2015 22:26:47 GMT -5
I want you to do a continuity test from the power connector to those 2 pins on that regulator. See if the center pin shows continuity to 1 of those pins and then the barrel connection to the other pin.
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Post by justgreg on Feb 28, 2015 23:19:20 GMT -5
*Power connector center pin to leg 1 of regulator = continuity. No continuity to any of the other 3 legs on the regulator.
*Power connector ground = The only leg with continuity is #2
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Post by mastertech on Mar 1, 2015 0:13:12 GMT -5
Ok, that is just what it should be by what I see. Next test will be powered up. Leave that diode disconnected like it is. Connect the power supply but have the switch on the power strip off. Set your DMM to DC voltage. Put neg probe on pin 2 and pos probe on pin 1. Flip switch on and see if you have +5v. If you do, then leave the neg probe where it is but put your pos probe on the bottom left pin and see if you have 3.0v If you do, then put pos probe on end of diode that is not connected and see what your voltage is and let me know. Good luck. |
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Post by justgreg on Mar 1, 2015 15:37:56 GMT -5
Love it. The plot thickens!
Results to follow in a bit.
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Post by justgreg on Mar 1, 2015 18:54:28 GMT -5
OK. We got the voltages you expected in steps 1&2. Got +5.xx at the end of the diode. Not sure I mentioned it earlier but the pad the diode end normally solders to has continuity to ground. Where to next Yoda?  |
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