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Post by danno27 on Jun 22, 2015 12:23:05 GMT -5
well, to me, 0 and 001 are shorted, their internals have been fried by something. The others... outputting a weak signal? I don't know what the values should be. I know a 1K resistor should be within 989 to 1001 ohms but I don't know a hell of a lot about transistors, I haven't worked with them yet. Are these values similar to capacitance reactance and inductance reactance values? I'll look up the spec sheet for these...
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Post by gjaky on Jun 22, 2015 12:45:35 GMT -5
well, to me, 0 and 001 are shorted, their internals have been fried by something. The others... outputting a weak signal? I don't know what the values should be. I know a 1K resistor should be within 989 to 1001 ohms but I don't know a hell of a lot about transistors, I haven't worked with them yet. Are these values similar to capacitance reactance and inductance reactance values? I'll look up the spec sheet for these... Hint: all the transistors except the two that showed ~0 are fine! The multimeter in diode mode gives actually voltage reading, that means how much voltage drops on the P-N junction (in diode or transistor) what you probe on. A silicon diode drops about 0,6V, hence the reading. There are different semiconductors that drop less voltage. |
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Post by danno27 on Jun 22, 2015 13:05:34 GMT -5
Interesting, We touched on diodes a bit in my DC class, and I remember them dropping 3.3 volts if I remember right.
But for replacement, Sanken with part number C3519 should work. No? And there is 26 0 below that part number. I saw on a datasheet diagram, that number is a lot number?
Side note... A transformer just blew here in my neighborhood.. I'm outside on the back deck and I heard buzzing/popping, followed by a smell of burnt material. My laptop screen flickered from the brownout... I remember seeing the light from one of those things blowing...
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Post by mastertech on Jun 22, 2015 14:39:27 GMT -5
Yes, the ones reading .001 or 000 are bad. The others are ok. Generally speaking you do not need to know what the readings on a good one should be. They almost never just go off in readings. They are almost always good or shorted. Next you need to check and see what else has been damaged. I have attached the schematic so you can check the value of any resistors. Here is your list: These are all R's: 24,3,5,9,28,41,40,39,11,7,10,29,42,37,38,25,2,4 Also test transistors; Q13, Q15, Q3 So the 2 transistors that are blown are both 2SC3519? |
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Post by mastertech on Jun 22, 2015 14:47:42 GMT -5
One more thing I would also like to note. I see in your testing pin post that you did not do any testing also using pins 2 to 3. This pin arrangement should also be checked with test leeds both ways to be certain there is not a short just between those 2 pins and the other pins read fine.
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Post by jeremy on Jun 22, 2015 16:08:08 GMT -5
What do you think when you see these readings? Ooooo, I know!!! But I wont say anything, not my thread! Enjoying seeing the progress though, I have a Parasound HCA3500 so this caught my attention. Good luck with the repair! (Y) |
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Post by jeremy on Jun 22, 2015 16:09:58 GMT -5
I see I'm late to the game!  |
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Post by danno27 on Jun 23, 2015 10:45:36 GMT -5
I see I'm late to the game! Yeah, I'm a bit late too... My power has been off for almost 12 hours, 3 or 4 transformers blew, so PPL crews were out until like 2 AM last night. That is rare... Usually never goes out. Interesting, I was outside to hear them pop and sizzle, followed by the smell. So time to test these resistors. Guess I'll have to de-solder them all. Thanks for the schematic, I think I have it though. And yes they are both 2SC3519... And yes, I'll also test the other transistors on the board. Seems like a good idea. |
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Post by danno27 on Jun 23, 2015 14:42:29 GMT -5
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Post by danno27 on Jun 23, 2015 14:49:51 GMT -5
One more thing I would also like to note. I see in your testing pin post that you did not do any testing also using pins 2 to 3. This pin arrangement should also be checked with test leeds both ways to be certain there is not a short just between those 2 pins and the other pins read fine. Thanks for pointing that out... |
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Post by mastertech on Jun 23, 2015 15:07:58 GMT -5
Well I am not sure I see the discoloration you are talking about but everything looks pretty normal to me.
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Post by jeremy on Jun 23, 2015 17:34:24 GMT -5
I can see what he's talking about, but it's so slight that the component that warmed up enough to make it change color slightly is likely fine, board discoloration is normal when there is any heat usually. I don't think I would worry about it.
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Post by danno27 on Jun 30, 2015 9:37:14 GMT -5
I doubt anybody is following this thread anymore, but I have a question about resistors. I bought a whole mess of metal film resistors on ebay. They are 1/4 watt and I don't know if they're good enough to replace the existing ones. I figured I'd just replace all of them. The leads feel a little thin. How can I know I'm getting ones that are adequate enough? I know one on the schematic says 2w. but that is a larger one. And I scratched the outer coating on one of the larger 3 w resistors. didn't know if that would be a problem. And I'll probably have to put a wire to connect the one transistor to the neighboring resistor because I damaged the pad while de-soldering the one transistor. I don't know what kind of abuse is too much for these boards. I'm trying not to damage it while using my heated desoldering gun.
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Post by mastertech on Jun 30, 2015 9:50:48 GMT -5
If the schematic says 3 watt then you have to use 3 watt or larger. If it says 2 watt then you have to use 2 watt or larger. If it does not show a wattage rating then there is usually a legend to indicate what size is to be used but this schematic does not have that. So generally you would go by the size of the originals or larger.
When repairing a broken trace the size of the wire to be used should be considered by the size of the trace itself. Not necessarily by the width of the trace but compared to the wire if it were flattened out and flattened thickness. But not needed to be to critical. Most of the time people use a wire that is way bigger then what it required.
Scratching the coating does not affect the resistor.
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Post by danno27 on Jul 15, 2015 13:35:11 GMT -5
Just about to finish up this repair, one last thing, testing the Q3 C2240 Transistor and I'm not sure what my readings on this should be. I had a hell of a time getting that out of the board for testing. Can I replace with a general purpose NPN type if need be? Everything else is fixed, just need to flux and reflow some of the joints, I keep getting cold solder joints. Probably, nobody is following this post anymore though...
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