At the end i changed the resistors, i tried deferent brand but stayed at 1 Ohm. And changed c204 from 15nf to 10nf.
I also tried 0.1 ohm but the mosfet was running loud and the startup of the welder was not smooth so I think 1 ohm is a must.
I really Really appreciate your BIG help in this project!!!
You are amazing!...
Olles4
Senior Member
Last Activity: 01-28-2025, 09:36 PM
Joined: 04-06-2022
Location: Tvrdošovce
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Alright i used 10nF capacitor and bought new resistors and it's running.
What kind of thermal paste should I use between components and heatsinks ?Leave a comment:
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Update:
I bought 1Ohm 1W +/-5% resistors and its not working it looks like the resistance is too big, if i short the resistor to GND screw-hole it runs. Any thoughts?
Btw from my perspective C204 looks like C205 by the size. C208 is way thinner.
C205 is 97nF (measuring de-soldered) what do you think ?Leave a comment:
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Thank you thats a valuable lesson!
I measured C208 and it’s 9.42nF so my guess is 10nF for both C208 and C204...Leave a comment:
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Why do you think it's same?
I mean I totally trusts you 😄 just want to know...Leave a comment:
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Okay tomorrow I will change it and it will run I’m pretty sure!
Just one thing is bothering me, c204 is a for current waveform spike suppression if I’m right, what is changing if you changes the capacitor value ?Leave a comment:
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its brown, black, gold, red it hard to see on the photo...Leave a comment:
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R205 and R206
oh I see, it’s R1 and R2 on the schematic.
by colour code it should be 1ohm +/-5% 2W(by size)
What do you think ?
The problem is i took down cap204 to measure it and unfortunately I broke it.. but on board I measured and it gave mi something between 15-18nFLeave a comment:
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I found something R205 and R206 are open
C204 15nF is a good value?Leave a comment:
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im using a K9J90E mosfet the old one was K3878
C201 is 103 2KV (10nF)
D201 new UF4007-E3/54 old BYV26E
R201 98.8kOhm
R205 and R206 should be 1Ohm am i right ?Leave a comment:
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okay but how should i deal with the over Voltage on Isense ?...Leave a comment:
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i used 1001 (1KOHM) Resistor for R209, should i try higher resistance ?
BTW im measuring on Gate or Surce of the mosfet only 2.4V...Leave a comment:
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oh shit but i have 2.6V on curent sense pin3...Leave a comment:
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c209 is jumpy but its something around 17 nanoF...Leave a comment:
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Hello. I have done some measurings. So on the small board the IC UC3843 pin6 (output to gate) is only 0,7mV and it seems like it didn't want to drive the mosfet
How much Volts should i get on mosfet Drain and Source ?
here is a link to ic [URL="https://html.alldatasheet.com/html-pdf/25582/STMICROELECTRONICS/UC3843BN/1622/1/UC3843BN.html"]UC3843BN datasheet(1/15 Pages) STMICROELECTRONICS | HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER (alldatasheet.com)[/URL]Hello. I have done some measurings. So on the small board the IC UC3843 pin6 (output to gate) is only 0,7mV and it seems...Leave a comment:
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These are the 2 connectors. So I assume the small board next to it what we were fixing it’s part of the supply.Leave a comment:
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So this is the front lcd panel with potentiometers and welding style adjustments with a small pcb it’s connected with 2 cables to the main boardLeave a comment:
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Nothing blown up just one of the heatsink was under voltage so it shocked me.. but it’s connected to diode which’s base is connected to the line.
I understand that but the problem is it didn’t even turns on....Leave a comment:
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