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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Cracked resistor?
On Tue, 04 Oct 2016 16:54:42 -0500, Tim Wescott wrote:
So, a customer sent me a board with the query "whuzzup?" It turns out that there's a resistor in there, which I mostly put in so that I could monitor current, but I kinda put in as a last-ditch fuse (1.5 ohm 0603). On this board, the resistor is open-circuit with no discernible burning. Is there some electronic mechanism that could cause this? Or am I just looking at a faulty part? I assume you've got your test prods directly on the pads so you know it's not just a dry joint? X-posted to s.e.r (more appropriate group) |
#2
Posted to sci.electronics.design,sci.electronics.repair
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Cracked resistor?
On Tue, 04 Oct 2016 22:08:17 +0000, Cursitor Doom wrote:
On Tue, 04 Oct 2016 16:54:42 -0500, Tim Wescott wrote: So, a customer sent me a board with the query "whuzzup?" It turns out that there's a resistor in there, which I mostly put in so that I could monitor current, but I kinda put in as a last-ditch fuse (1.5 ohm 0603). On this board, the resistor is open-circuit with no discernible burning. Is there some electronic mechanism that could cause this? Or am I just looking at a faulty part? I assume you've got your test prods directly on the pads so you know it's not just a dry joint? X-posted to s.e.r (more appropriate group) Yes. But making that mistake isn't beyond me, by any means. It's a very well-assembled board (I didn't do it), but well designed, too (I did it -- and I'm modest, just ask me). -- Tim Wescott Wescott Design Services http://www.wescottdesign.com I'm looking for work -- see my website! |
#3
Posted to sci.electronics.design,sci.electronics.repair
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Cracked resistor?
Cursitor Doom wrote:
On Tue, 04 Oct 2016 16:54:42 -0500, Tim Wescott wrote: So, a customer sent me a board with the query "whuzzup?" It turns out that there's a resistor in there, which I mostly put in so that I could monitor current, but I kinda put in as a last-ditch fuse (1.5 ohm 0603). On this board, the resistor is open-circuit with no discernible burning. Is there some electronic mechanism that could cause this? Or am I just looking at a faulty part? I assume you've got your test prods directly on the pads so you know it's not just a dry joint? X-posted to s.e.r (more appropriate group) Plenty of water and the whiskey bottle has been properly drained. |
#4
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Cracked resistor?
The dissipation power is 200mW max.
So I lower than 0.3A. If not, it burns ! Robert Baer a écrit : Cursitor Doom wrote: On Tue, 04 Oct 2016 16:54:42 -0500, Tim Wescott wrote: So, a customer sent me a board with the query "whuzzup?" It turns out that there's a resistor in there, which I mostly put in so that I could monitor current, but I kinda put in as a last-ditch fuse (1.5 ohm 0603). On this board, the resistor is open-circuit with no discernible burning. Is there some electronic mechanism that could cause this? Or am I just looking at a faulty part? I assume you've got your test prods directly on the pads so you know it's not just a dry joint? X-posted to s.e.r (more appropriate group) Plenty of water and the whiskey bottle has been properly drained. |
#5
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Cracked resistor?
On 10/04/2016 06:08 PM, Cursitor Doom wrote:
On Tue, 04 Oct 2016 16:54:42 -0500, Tim Wescott wrote: So, a customer sent me a board with the query "whuzzup?" It turns out that there's a resistor in there, which I mostly put in so that I could monitor current, but I kinda put in as a last-ditch fuse (1.5 ohm 0603). On this board, the resistor is open-circuit with no discernible burning. Is there some electronic mechanism that could cause this? Or am I just looking at a faulty part? I assume you've got your test prods directly on the pads so you know it's not just a dry joint? X-posted to s.e.r (more appropriate group) Hello, and the only similar problem I've encountered is with those sandy-colored dropping resistors (rectangular parallelepiped shaped) that have been used in radios and TVs. They can swell and/or crack over a period of time. Repeated heating and cooling no doubt stresses the resistor material. Sincerely, -- J. B. Wood e-mail: |
#6
Posted to sci.electronics.design,sci.electronics.repair
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Cracked resistor?
J.B. Wood wrote:
On 10/04/2016 06:08 PM, Cursitor Doom wrote: On Tue, 04 Oct 2016 16:54:42 -0500, Tim Wescott wrote: So, a customer sent me a board with the query "whuzzup?" It turns out that there's a resistor in there, which I mostly put in so that I could monitor current, but I kinda put in as a last-ditch fuse (1.5 ohm 0603). On this board, the resistor is open-circuit with no discernible burning. Is there some electronic mechanism that could cause this? Or am I just looking at a faulty part? I assume you've got your test prods directly on the pads so you know it's not just a dry joint? X-posted to s.e.r (more appropriate group) Hello, and the only similar problem I've encountered is with those sandy-colored dropping resistors (rectangular parallelepiped shaped) that have been used in radios and TVs. They can swell and/or crack over a period of time. Repeated heating and cooling no doubt stresses the resistor material. Sincerely, Some of those are 'Fuse Resistors', and are designed to fail open if the equipment starts drawing too much current, or if it is running too hot. I replaced hundreds, if not thousands of those in consumer electronics. Some OEMs switched to the Belfuse 'Chemical Fuses', which had a chemically coated element that would flash and vaporize the element at a set temperature. They were quite common, in spite of Phil Allison's claim to the contrary. -- Never **** off an Engineer! They don't get mad. They don't get even. They go for over unity! ;-) |
#7
Posted to sci.electronics.design,sci.electronics.repair
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Cracked resistor?
Look165 wrote...
The dissipation power is 200mW max. Not much safety margin for an 0603. -- Thanks, - Win |
#8
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Cracked resistor?
"Winfield Hill" wrote in message ... Look165 wrote... The dissipation power is 200mW max. Not much safety margin for an 0603. -- Thanks, - Win Isn't that at 25 °C? |
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