Hakko FR-300 Dead PCB Powerless Heating Element Whats the Diode? - Page 1
Forum section: electronics / repair

author: LuckyLarry
author_rank: Newbie
timestamp: March 03, 2019, 02:44:54 pm
content: Hey guys. So I'm new to The forum here, so I do apologize if this particular problem and or subject has been covered I tried searching but couldn't find anything specific to what I was asking and I've been searching for 6-7 hours(today lol) trying to figure out what this diode is. Endless datasheets, Google searches, forms, YouTube videos, everything possible. I have some... common electronics knowledge, but I am new to the whole SMD stuff so this is a little outta my depth.. There are so many different diodes and I have no idea what would work or not work or If I can just replace it with anything? I have no way to test the value with my ESR meter because it's open and it's showing OL both directions, out of circuit. I'm stumped.. I've been staring at the screen so long not getting anywhere, so I figured I would try this forum and hopefully someone would be able to help me out or point me in the right direction or give me some answers/help to something that is probably super simple or that I am just overthinking because I just don't understand Or have the proper knowledge.But I guess a little background on what happened exactly and what caused the diode to go poof... I decided to do an LED mod(really regretting it now lol) because I cannot stand the terrible location of the red heating element LED. I've left it on numerous times after getting sidetracked and forgetting it was on because you can't see the LED. Wile I was testing the connections to see what was suitable to hook up an LED to for DC power I some how hit the mains leads with my hand gave me a little zap so out of reflex it caused me to jump and flail like a girl.. and my probe hit something or grounded out a post. after it happened I put it back together everything worked normal except the heating element won't heat but the vacuum still works. after weeks and weeks and endless testing and buying random parts and trouble shooting trying to replace things 1 by 1 I finally came to the conclusion that I think there's a short to ground or ground short? Quite a few of my resistors/capacitors are having continuity, but I'm pretty sure I figured out finally the issue is this diode.. maybe I'm wrong yet again, but who knows. that's why I'm asking trying to get some input. But it does make sense because the diode is in the path with what I shorted out and popped that or causing it to go bad. I think it is causing these ground shorts(not sure if that's the right term?) and continuity issues. But I'm just going off of what I've read and researched so I could be wrong there too. I would really appreciate any input or any info anyone has or any direction someone can point me in to help me fix this thing. I know I can buy another circuit board but it's the fact of the matter that I want to fix it! at this point really bugging me and I can't let it win lol thanks!! -Larry

author: royarms
author_rank: Newbie
timestamp: March 03, 2019, 06:59:36 pm
content: https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.diodes.com/assets/Datasheets/ds30588.pdf&ved=2ahUKEwj558jJ0-bgAhWG14MKHZfcCVMQFjAAegQIARAB&usg=AOvVaw3u7FtueVrUBi-kDndnNIlfGoogle "smd code LJ diode" first resultSent from my SM-G900V using Tapatalk

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: March 04, 2019, 03:46:39 am
content: Where are you measuring a short?D1 is between the mains input (just after the power switch) and the low voltage, digital ground - it would have failed pretty spectacularly if it were dead, but the vacuum motor wouldn't work eitherDoesn't look like anything has obviously blown, can you take a photo of the board straight on, particularly the area below the power switch/trigger and those big resistors?

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: March 04, 2019, 03:47:50 am
content: Also, I wouldn't expect it to make any difference, but have you tried fitting the original LED back in?

author: helius
author_rank: Super Contributor
timestamp: March 06, 2019, 05:48:54 am
content: Before looking all over the circuit board, have you tested the heater itself? The resistance between the white wires should be 50Ω, and the resistance between the red wires should be 35Ω. Testing resistance between white and red should be OL.

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: March 06, 2019, 11:32:17 am
content: Measuring a short, as in measuring zero (or very close to zero) ohms between two points, a "dead short". If you're measuring 0 ohms across those capacitors then one or more components has failed short, and is shorting a power supply rail to ground.Using the continuity mode to test a capacitor might be misleading you; a discharged capacitor will present as a short initially, but the multimeter will charge up the capacitor(s) over time and subsequently read a higher resistance. Measuring continuity of a working capacitor will produce the beep initially, the resistance reading will rise, eventually displaying "OL", and the beep will stop.