How to figure out whats is wrong or replace. Bosch mulcher board - Page 1
Forum section: electronics / beginners

author: kjh
author_rank: Newbie
timestamp: October 15, 2020, 02:20:38 pm
content: Greetings, After lurking here for several years I decided to get my head out of the place it has been.I have basic understandings of how things work. But I am in the deep end now. I hope that someone could help me with how to get to the next level.This circuitboard is from an awsome mulcher. But It is stuck in a loop of alarming that one of the safety switches is triggered. Trust me they are not.The connector marked with black goes to a big ass electric motor.The white connector is incoming and connected to three switches that makes sure that certain components are properly placed. If they are it is a closed loop between right and left pin.The small white connectors are to some other switches that opens when other things arent properly placed.I dont care about all the safetyswitches, you have to be an idiot to get injured even if they arnt in place. I am aware that it will be on my own risk. And if you didnt get it from my probably mixed english, I am not an american and in sweden we cant sue eachother anyway.So why am I posting?I have obviously taken out the triacs and they give the same measurements and will obviously be replaced since they miss a leg each now... (bosch uses really good "glue") but I then dont think that they are broken so I start to think the greenpainted tiny "brainbox?" is the problem and well That seems difficult to replace.The issue is that it only beeps and blinks with the green leds. it responds to the buttons but only with blinking lights. and the beeping is never ending. according to the manual it is like that when a safetyswitch is triggered. And before the board came out It has been tested with the safetyswiches in ALL positions several times... I have even yelled safetywords while working on it still not safe enoughQuestion AWhat can I do to get further? apart from replacing the by me broken triacs...(the white wired safety cables were only shorted to them selves when i tested them but I at somepoint had nervous fingers and combined all 4)Option BSince I dont really care about the safety switches I would be fine to just make the motor turn when I push a button and honestly that button kan be on the mains line for all i care.But there are more cables to the motor then I am accustomed to. White, yellow, red, blue But I dont know even how to start figuring out what too look for to figure that out.

author: larrybl
author_rank: Regular Contributor
timestamp: October 15, 2020, 04:07:50 pm
content: I am assume this is a type of lawn mower. I am a member of several forms that discuss mowers up to full size tractors. Most "all" have safety switches which constantly cause problems. One thing that is NOT discussed is how to by-pass these. If someone tells you how, and something bad happens then you can guess the rest.Hopefully you can find a diagram and trouble shoot and fix the problem correctly.

author: Alti
author_rank: Frequent Contributor
timestamp: October 15, 2020, 06:27:25 pm
content: Hi, welcome to the forum.What I recommend:1. Find the model numbers of that gear. If it was expensive, there is a good chance the questions you ask have already been asked by someone else. By that I mean do not expect the only model number to be the one on warranty card but start there. Google, compare photos of various equipments of this type, versions, do not focus on Bosch and green because it might actually come from somewhere else and rebranded. Maybe same PCB was also in some other lawn mower. eBay. I am sure you get the concept.2. In era of RoHS, the vibrating equipment tends to fail by cracked solder joints. This happens when for example a big THT is held by tiny solderpads. Stop destroying PCB, take a microscope/magnifying glass and try to find THT components with cracked solder joints. Do not fix or crack it, just find if there are any. Unfortunately you managed to ruin two triacs already so you might have already destroyed the cause of the problem making repair even harder. Cracked joint is quite difficult to find so YT to know what to look for.3. This PCB is double-sided. This isveryunusual in this type of equipment but also makes THT bond much stronger. Unfortunately adds the problem of vias. These tend to crack when subjected to thermal stresses. This could be one of further causes.4. Board has quality components (BTB24-600 is one of more expensive TO-220 triacs, I mean like €2 instead of €0.2 16-amp version) which means it was not optimized for BOM (which is great). I really doubt any components coud fail there.5. Do not try to touch the board while it is powered because nothing on that board is isolated.6. This "brain" with green stripe is a microcontroller. If it is damaged then you won't be able to fix this thing. From your description it seems it is OK.

author: kjh
author_rank: Newbie
timestamp: October 16, 2020, 08:04:52 am
content: @larrybl It is one of these.So as long as you dont put your hands into the hole with the rotating knives, it wont be a problem. It cannot run you over or anything.@AltiThank you1. the spare part is kind of expensive (half the price of a new machine) Forum posts where people have the same issue have been under warranty and just got a replacement board from Bosch. And if I had been interested to learn how to swamp one part for another I would seek out a career as a brand name automechanic.(i know that there is car mechanics that are really good at repairing cars out there as well)My point is that I want to learn to repair or atleast figure out what is wrong with boards since everything has them these days.2. yes they are destroyed now, but I knew that they probably would be when I needed to drill them out of the board. they were REALLY well attached with rivets and glue. But I dont know any good way I could test them in circuit.And they seemed to be the most likely to have overheated since there was alot of debree covering the aluminium plates. (my neighbor who threw it out didnt give it enough love)I use a lens from a projector as a magnifying glass and I have not seen any cracks nor found them whit the ohm meter But the board is really well coated so the ohm metering is difficult.5. Thank you I am aware that this is a board not ment to lick while plugged in, but i understand and respect that you points this out. If I had not know (or anyone else) it would be unnecessarily interesting if you touch it when plugged in.No one seemed keen on the idea to simplify the thing by having just a forward and reverse option with an easier Cicruit

author: Alti
author_rank: Frequent Contributor
timestamp: October 16, 2020, 09:42:07 am
content: Quote from: kjh on October 16, 2020, 08:04:52 amhttps://www.bricoleurdudimanche.com/forums/forums-jardinage/forum-outils-du-jardinier-212/remplacement-des-triac-pour-le.htmlDo your homework and google.QuoteDoes not seem so.

author: kjh
author_rank: Newbie
timestamp: October 16, 2020, 05:34:01 pm
content: Thank you Alti I understand that you also speak french and that you are registered on the other forum as Gerard22. And I understand answering the same question twice is bothersome for you.I admit my French google foo is limited. I only tried to google in the 5 languages I know, French is not one of them.But I understand that the place to get help on my endeavor to learn might not be on this forum. It is for people that already knows.I’m sorry that I caused you so much trouble.