Electronics > Repair
miller dynasty what is precharge relay
SteveThackery:
--- Quote from: coppercone2 on August 26, 2024, 04:40:31 am ---
I guess the solder needed a bit of time to set (people have a misconception that it works as soon as its solid) ??? I have no other explanations.
--- End quote ---
A joke?
coppercone2:
You tell me. It needed to rest with the new components for a while before it works. All people can do is blame the card contacts but they look great to me. I cleaned them very well and inspected all of it with a 14x magnifier
Honestly what it reminds me is de-gassing a radiator for a house or something, after you do plumbing you got the air bubbles that take about that amount of time to really come out. Maybe the circuits get loaded up with bad electrons or something. They get stale in storage and need to be drained into the circuit. The machine was plugged into earth ground during this rest period. :o
Professionally at work of course you would just blame some kinda nebulous mechanical contact related effects or tin whiskers or what ever there is in the "old thing dont work" box of tricks, if you had to write a report to sate someone about a transient issue. Personally I think there might be more to it
coppercone2:
I got the fucking flaky conformal coating off the main board (wow that took an hour and like 1/2 liter of solvent), plus 100 task wipes, so I can replace the sensor and inrush relay, just incase, because they were connected to the dodgy PCB with the bad CD and op amps.
The machine was working before but I figure I should not leave it in the shop with a conformal coating that looks like it has the morphogenic changling virus
What a god damn mess. It turned into like... pizza crust blisters on the bottom. Wow i hate conformal coating. >:(
I don't know why. Maybe I turned it on too soon the first time I fixed it and it caused residual solvent to evaporate too soon before it was cured, but I dunno. I guess I should wait like a week >:(
coppercone2:
now some fucking resistors blew up >:(
I have a feeling this whole thing is under rated, they should have used 1/2 watt metal oxide parts instead of this film bullshit on the high voltage part.
I wonder how well it would drag behind my car :horse:
I almost want to make it my lifes work to remake this entire thing with heavy copper PCB (double thick fiberglass), with isolation traces, 300% bigger parts, and see if its still a piece of shit. it baffles me
I want to know if its actually a bad circuit that is unreliable or just shitty finite element engineering where they think they can predict everything to keep shaving the BOM to nothing. The only reason I keep working on it is because the parts are so cheap in comparison to the machine.
I wonder if it has the electrical equivalent to 10-32 screws holding on a truck tire.
I have a feeling every single component on those little PCB cards is basically electrically over stressed for any reasonable reliability at that voltage. All the parts near the card inputs near HV on the boost and inverter control card probobly need a change to a more durable resistor. This machine has "lol 1/4 watt" disease
"mains is never gonna be more then 124V AC with the 270V mov right?"
"the power is 249.95 miliwutts in the simulator!"
"don't worry, I put a nichicon capacitor!"
"the monte carlo is a casino right?? you want me to do a team building exercise there??"
- miller expert project engineers
Maybe I can scan the boards and we can have a betting pool on which one will blow up next
finding the deficiencies in their design is more fun then actually welding I suppose.
You need to be like Stalin to fix this thing. Kill everything that might even look at you the wrong way in the future. I just feel paranoid and I keep wanting to replace more and more parts. its not a good design that makes you feel like this after only ~10 years. :(
Fortunately there is a river between the two cities, There is a few suspicious grain silos that need to be cleansed on the other side.
I found brown residue under one of the 1000 ton grain silos.
Somehow I managed to burn my nose doing battle with the scourge
And the weird thing is, the resistor that blew, it blew hard, its 1500 ohm, and it left a crater in the PCB. THats a fairly high value resistor. I don't think it failed naturally. It went bang, not pop. wtf. I wonder if the resistor was fucked up and soaked up solvent from when the PCB was being cleaned or something. Or maybe the old conformal coating under the resistor had conductive material diffuse into it and blew up :-\
coppercone2:
I think the problem is that after i fixed it, I decided to replace more parts, and I replaced a 2n3906 with a 2n3904 transistor, because there is some severe confusion on another form that I followed, it made me feel that my mind was playing tricks on me because people were agreeing with the incorrect component.
I finished replacing all the IC's on the card, the damaged parts, and all transistors on that island with the correct parts, along with the blown IGBT and diode and shunt.
I am ready to try to reassemble it. The tests on the big parts seemed to show that none of the expensive crap got damaged.
So the only problem could have been a mistake, and not the conformal coating
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