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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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Verify a(maybe) dying diode caused by a bad capacitor???
I have just fixed an power supply by replacing a bulging capacitor.
The capacitor is connected to diode. And the diode becomes hot and makes a black spot on the board since the faulty cap. I check the diode with a multimeter and it tests great. The repaired power supply( cap replaced) has been tested for several hours and no problem yet. Question: Is there any way to check whether the diode is working 100% ? Thanks! |
#2
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Verify a(maybe) dying diode caused by a bad capacitor???
wrote in message oups.com... I have just fixed an power supply by replacing a bulging capacitor. The capacitor is connected to diode. And the diode becomes hot and makes a black spot on the board since the faulty cap. I check the diode with a multimeter and it tests great. The repaired power supply( cap replaced) has been tested for several hours and no problem yet. Question: Is there any way to check whether the diode is working 100% ? Diodes are cheap. It was stressed. Replace it. |
#3
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Verify a(maybe) dying diode caused by a bad capacitor???
On Mar 12, 4:31 pm, wrote:
I have just fixed an power supply by replacing a bulging capacitor. The capacitor is connected to diode. And the diode becomes hot and makes a black spot on the board since the faulty cap. I check the diode with a multimeter and it tests great. The repaired power supply( cap replaced) has been tested for several hours and no problem yet. Question: Is there any way to check whether the diode is working 100% ? Thanks! It seems like the repair worked, but the hot diode concerns me. Your description is a little hard to understand. Did the diode get hot before or after the capacitor was replaced? In any case, the black mark by the diode isn't a good sign. Whether the mark was cause by the diode overheating or leakage from the bulging capacitor, I would replace it. As another poster tersely pointed out, diodes are inexpensive. For a definitive measurement, don't test the diode in place. Rather, unsolder one of its leads from the circuit board and then test it with your voltmeter's continuity checker. -Dave |
#4
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Verify a(maybe) dying diode caused by a bad capacitor???
By your descriptions it looks like your supply is working fine. It is
normal for some components to warm up and if it were faulty you would see some problem with your supply. If it works, don't mess with it. wrote: I have just fixed an power supply by replacing a bulging capacitor. The capacitor is connected to diode. And the diode becomes hot and makes a black spot on the board since the faulty cap. I check the diode with a multimeter and it tests great. The repaired power supply( cap replaced) has been tested for several hours and no problem yet. Question: Is there any way to check whether the diode is working 100% ? Thanks! |
#6
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Verify a(maybe) dying diode caused by a bad capacitor???
"Jeroni Paul" wrote in message ups.com... By your descriptions it looks like your supply is working fine. It is normal for some components to warm up and if it were faulty you would see some problem with your supply. If it works, don't mess with it. wrote: I have just fixed an power supply by replacing a bulging capacitor. The capacitor is connected to diode. And the diode becomes hot and makes a black spot on the board since the faulty cap. I check the diode with a multimeter and it tests great. The repaired power supply( cap replaced) has been tested for several hours and no problem yet. Question: Is there any way to check whether the diode is working 100% ? Thanks! I see lots of bulging caps in the power supplies of cheapo DVD players - I probably repair 2 or 3 a week on average. I have found it very rare indeed for the feeding diode to actually be faulty. Usually, it's just a case of replace the cap, and that's it. It is not at all uncommon for the diodes in these supplies to run very hot, and discolour the board. Sometimes, if there is room, I bend a small piece of metal around the body of the diode, with a bit of heatsink paste in there as well, to help cool it down a bit. Bear in mind if you do replace it that it will be a Schottky type ( I'm assuming that this is a switch mode PSU ??? ) Arfa |
#7
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Verify a(maybe) dying diode caused by a bad capacitor???
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#8
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Verify a(maybe) dying diode caused by a bad capacitor???
Jeroni Paul wrote: By your descriptions it looks like your supply is working fine. It is normal for some components to warm up and if it were faulty you would see some problem with your supply. If it works, don't mess with it. Bad advice. Some components may have been stressed by the fault The charring near the diode indicates this. There's NO WAY to prove the diode hasn't had its reliability compromised through overheating so it should be replaced as a precaution. Graham |
#9
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Verify a(maybe) dying diode caused by a bad capacitor???
Arfa Daily wrote: Bear in mind if you do replace it that it will be a Schottky type Or a fast-recovery type. Using a standard diode will guarantee long term failure although it might work for a bit. Graham |
#10
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Verify a(maybe) dying diode caused by a bad capacitor???
Eeyore wrote:
Bad advice. Some components may have been stressed by the fault The charring near the diode indicates this. There's NO WAY to prove the diode hasn't had its reliability compromised through overheating so it should be replaced as a precaution. The charring proves that the diode has always run hot and it is likely the way it is meant to be. A board is not charred in just a few hours of operation. Messing and replacing these diodes is a good way to risk the power supply, and given that it runs hot I would be very careful with the type I replace it with, get it wrong and you may blow the supply again. |
#11
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Verify a(maybe) dying diode caused by a bad capacitor???
On 12 Mar 2007 19:12:49 -0400 Sam Goldwasser
wrote in Message id: : writes: For a definitive measurement, don't test the diode in place. Rather, unsolder one of its leads from the circuit board and then test it with your voltmeter's continuity checker. If it tests good in-place, it won't test bad when removed. Unless the in-circuit test is turning on a junction of another semiconductor that's in the same circuit, and the diode is open. |
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