Idenfitying a diode - Page 1
Forum section: electronics / beginners

author: Pcmaker
author_rank: Regular Contributor
timestamp: October 21, 2017, 09:33:46 pm
content: I posted a problem about my DeWalt battery charger here a few days ago and I found a bad diode today right next to the transformer, buried under some glue. It's hard to read and hard to figure out which number/letter is the starting one.I'm getting 0.000 either way I test the diode with my multimeter.I think the correct order isBYV26EGPand has "451" under itI'm going to replace this diode to see if this is the problem. datasheet:https://www.vishay.com/docs/88554/byv26dgp.pdfI'm going to Fry's electronics tomorrow to replace this diode. What characteristics should I be looking for? Max voltage and size? Is "451" the voltage you're supposed to get when you test it with the multimeter's diode function?

author: ebclr
author_rank: Super Contributor
timestamp: October 21, 2017, 09:44:11 pm
content: Very importantIF(AV) 1.0 AVRRM 800 V, 1000 VsecondaryIFSM 30 Atrr 75 nsThis diode can be replaced with many types, nothing special

author: Old Don
author_rank: Regular Contributor
timestamp: October 22, 2017, 02:47:35 am
content: 451 is most likely a date code - 51 week of 2014, 2004 or 1994 or .....A multimeter does not put out voltage equal to a diode's breakdown voltage. It measures resistance measured by reading the voltage dropped across an internal resistor from the internal battery powering the meter. No current flow equals high resistance and max current (as designed) equals a short.You need a diode designed to handle the current flow of your charging circuit plus also exceeding the highest voltage the diode will see - if it is direct off mains then at least 1.5 times input voltage. Since a 1000 volt diode costs about the same as a 200 or 400 volt diode in many cases you can fudge and just go with a 1000 volt diode. But the current rating can not be exceeded or you will be back to buy a 2nd replacement soon.A 1N4007 is a one amp diode rated for 1000 volts and is easy to find. Don't know if it is what you need or not.

author: Pcmaker
author_rank: Regular Contributor
timestamp: October 22, 2017, 09:21:05 pm
content: This is the only 1000v Fry's had, but it's 3amp maxWills this work?

author: Pcmaker
author_rank: Regular Contributor
timestamp: October 22, 2017, 10:30:31 pm
content: Quote from: blueskull on October 22, 2017, 10:22:43 pmThe bad diode was buried under all that white epoxy right above the transformer, right next to the R3 resistor and the sleeved resistor.

author: Pcmaker
author_rank: Regular Contributor
timestamp: October 22, 2017, 10:39:45 pm
content: Quote from: blueskull on October 22, 2017, 10:33:20 pmHow do you know if a diode is an ultra fast recovery diode or not? Is there a symbol?

author: lilshawn
author_rank: Regular Contributor
timestamp: October 22, 2017, 10:41:50 pm
content: it's specified in the datasheet. typically UFR diodes are used on the output of SMPS because of the high switching frequencies used. A regular diode does not switch fast enough to block.

author: Pcmaker
author_rank: Regular Contributor
timestamp: October 22, 2017, 10:44:49 pm
content: Are Ultra Fast Rectifier diodes the same as Ultra Fast Recovery diodes?

author: Pcmaker
author_rank: Regular Contributor
timestamp: October 22, 2017, 11:06:36 pm
content: Quote from: blueskull on October 22, 2017, 10:54:03 pmIt only has to have a trr spec or does it have to be faster than certain amount of time/nanoseconds to be considered a UFR diode?

author: Pcmaker
author_rank: Regular Contributor
timestamp: October 22, 2017, 11:22:54 pm
content: Quote from: blueskull on October 22, 2017, 11:17:18 pmThanks!I'm very new at this, but I'm learning multiple different things every day and I'll eventually become competent and more importantly, not have to bother people asking so many dumb questions.

author: ElektroQuark
author_rank: Unknown
timestamp: October 23, 2017, 07:46:06 am
content: Do they really sell super cheap components ONE BY ONE in blister package?The handling and packaging will increase the price by a hundred.

author: Pcmaker
author_rank: Regular Contributor
timestamp: October 23, 2017, 10:49:49 am
content: Thinking of getting this as a replacement. I wish I could only buy a couple pieces in town. If Fry's doesn't carry these, then I'm guessing nobody in the city does. I don't want to pay 15 bucks total for a set of them from Amazon.https://www.amazon.com/McIgIcM-200pcs-Standard-Through-DO-204AL/dp/B071KKHBGC/ref=sr_1_1?ie=UTF8&qid=1508755704&sr=8-1&keywords=UF4007

author: Mjolinor
author_rank: Frequent Contributor
timestamp: October 23, 2017, 11:42:49 am
content: Rob one from something old and broken. Most modern things will have one in.