charlton1706
New Member
- Messages
- 24
- Location
- doncaster
- Thread starter charlton1706
- Start date
charlton1706
New Member
- Messages
- 24
- Location
- doncaster
Also I’ve found this I’ve highlighted the three that are getting power and charging looking at it though it looks like they all 6 should power together or am I missing something?
charlton1706
New Member
- Messages
- 24
- Location
- doncaster
charlton1706
New Member
- Messages
- 24
- Location
- doncaster
Robert Weaver
Forum Supporter
- Messages
- 442
- Location
- Belper
that diagram really helps.
the 3 that are not getting power might indicate the IGBT on the left has failed short circuit, which is causing the full voltage from the bridge rectifier to appear across the 3 capacitors you've highlighted (which are charging). can you trace back to find the component part number on the IGBT ?
the 3 that are not getting power might indicate the IGBT on the left has failed short circuit, which is causing the full voltage from the bridge rectifier to appear across the 3 capacitors you've highlighted (which are charging). can you trace back to find the component part number on the IGBT ?
charlton1706
New Member
- Messages
- 24
- Location
- doncaster
Hi Robert cheers for the reply mate I’ve taken a photo and highlighted the igbt also the capacitors that are getting the power this might sound daft but should they be continuity across them?
thanks again for your time mate
thanks again for your time mate
charlton1706
New Member
- Messages
- 24
- Location
- doncaster
charlton1706
New Member
- Messages
- 24
- Location
- doncaster
charlton1706
New Member
- Messages
- 24
- Location
- doncaster
Sorry they are k50T60
Robert Weaver
Forum Supporter
- Messages
- 442
- Location
- Belper
capacitors shouldn't have resistance to DC (they're typically made of rolled dielectric insulator which polarises and stores electon charge) but if your DVM uses a frequency to measure resistance it might be fooled by seeing reactance. there's some SMD resistors soldered on the board across the capacitors (R38/R38-1 and R39/R39-1 above) which may give a false reading (unlikely, they're 51k ohm each). you'd need to desolder each cap to test if you wanted to be sure.
IGBTs are arranged as transistor and MOSFET like...
to test, there's some guidance on the web (here) which advises there should be normal diode behaviour in one direction, and open (infinite resistance) in the other direction. again, you'll need to desolder each to check properly since the link asks to short gate to emitter. if you're getting continuity in both directions, the IGBT is faulty.
(Just measured the resistance of some 680uF and got 35.6M ohm.)
IGBTs are arranged as transistor and MOSFET like...
to test, there's some guidance on the web (here) which advises there should be normal diode behaviour in one direction, and open (infinite resistance) in the other direction. again, you'll need to desolder each to check properly since the link asks to short gate to emitter. if you're getting continuity in both directions, the IGBT is faulty.
(Just measured the resistance of some 680uF and got 35.6M ohm.)
Robert Weaver
Forum Supporter
- Messages
- 442
- Location
- Belper
charlton1706
New Member
- Messages
- 24
- Location
- doncaster
Good call Robert I pulled all 4 ibgt’s 3 tested fine and one has continuity across all pins!
Are these two IGBTs the same component? i.e. the same location going short-circuit for a second time?
When IGBTs go short, they often conduct high voltages from collector/emitter circuits through to the gate, blowing gate driver circuitry. As I mentioned in #2, an IGBT with a floating gate can self-charge the gate capacitance, conduct fully on, and blow itself up, so you need to check the components on the gate before risking another IGBT.
charlton1706
New Member
- Messages
- 24
- Location
- doncaster
Hi Eddie49 no not the same one I replaced one next to it on the same heat sink though I will stick a pic up its my bad I should of pulled them before to check but the one I replaced was obvious so it thought wow get in and just changed that you live and you learn hey
charlton1706
New Member
- Messages
- 24
- Location
- doncaster
Yellow the one I replaced and red the one I’ve just found
Robert Weaver
Forum Supporter
- Messages
- 442
- Location
- Belper
Eddie is stressing the importance of exploring the root cause of component failure before ploughing on; once a failed component is found, replace it but go beyond and find why it failed in the first place. If it were the same component, and it's failed again, then a common cause is at play.
I'd second that sentiment every time. Find what's broke, then think why it broke and fix that, otherwise it's an expensive cycle.
I'd second that sentiment every time. Find what's broke, then think why it broke and fix that, otherwise it's an expensive cycle.
Darren, it is really good that you knew this machine was the same as the ESAB Buddy Tig, and you were able to find the circuit diagram. That makes things a lot clearer and easier to understand.
It is a functional diagram and does not show every detail. In particular, only two IGBTs are shown, but in reality there are four. I guess each one on the diagram is a pair, in parallel. I would suggest making a sketch by following the PCB tracks, to know which transistors are paired.
The IGBT gates are triggered alternately, to send current one way and then the other through the primary winding of the large transformer. This will happen at high frequency - 50 kHz or more. If one or more IGBT is permanently on, either because it is shorted or because it's gate driver circuit is damaged, excessive current will flow. As you have found, this high current can blow a capacitor, or an IGBT, or the thermistor if it has not yet been shorted-out by the timed relay. To prevent this kind of repeated failure, I suggested either using a Variac ( variable transformer ) instead of the straight AC mains, or a low-voltage current-limited power supply instead of the DC bus, during troubleshooting. Another trick is to use a bulb in series as a "visual dropper resistor". If the unit you are testing is OK, the bulb will light dimly as it shares the voltage with the device, but if there is a short-circuit in the unit the bulb will light at full brilliance.
You mentioned that you were feeding 24v to the board. I guess that this is DC, across the + and - wires that originally were the outputs of the mains bridge rectifier? If so, is this 24v current-limited ( such as a benchtop power supply ) ?, rather than 2 x 12v car batteries ...!! I think that 2 or 3 Amps is a safe limit.
You could limit the current with the lightbulb method, using 2 x 12v 21Watt car indicator/stop light bulbs in series across the "PTC Thermistor" location. Due to the low supply voltage when testing ( 24v instead of 325v DC ) I do not think the time-delayed relay will be operating to short that thermistor, so the current to the capacitors and to the power inverter will always flow through the thermistor location.
As I mentioned in post #33, the integrity of the gate driver circuits is very important, if the inverter is going to work again, and if repeated failure of new IGBTs is to be avoided. Before installing any replacement power transistors you need to trace the gate wiring, from the IGBTs ( Pin 1 from the left ) back towards the Control board.
As @Jan-DIY suggested in post #9 of this thread
there are often Zener diodes to protect the IGBT gates, so these must be checked.
It is a functional diagram and does not show every detail. In particular, only two IGBTs are shown, but in reality there are four. I guess each one on the diagram is a pair, in parallel. I would suggest making a sketch by following the PCB tracks, to know which transistors are paired.
The IGBT gates are triggered alternately, to send current one way and then the other through the primary winding of the large transformer. This will happen at high frequency - 50 kHz or more. If one or more IGBT is permanently on, either because it is shorted or because it's gate driver circuit is damaged, excessive current will flow. As you have found, this high current can blow a capacitor, or an IGBT, or the thermistor if it has not yet been shorted-out by the timed relay. To prevent this kind of repeated failure, I suggested either using a Variac ( variable transformer ) instead of the straight AC mains, or a low-voltage current-limited power supply instead of the DC bus, during troubleshooting. Another trick is to use a bulb in series as a "visual dropper resistor". If the unit you are testing is OK, the bulb will light dimly as it shares the voltage with the device, but if there is a short-circuit in the unit the bulb will light at full brilliance.
You mentioned that you were feeding 24v to the board. I guess that this is DC, across the + and - wires that originally were the outputs of the mains bridge rectifier? If so, is this 24v current-limited ( such as a benchtop power supply ) ?, rather than 2 x 12v car batteries ...!! I think that 2 or 3 Amps is a safe limit.
You could limit the current with the lightbulb method, using 2 x 12v 21Watt car indicator/stop light bulbs in series across the "PTC Thermistor" location. Due to the low supply voltage when testing ( 24v instead of 325v DC ) I do not think the time-delayed relay will be operating to short that thermistor, so the current to the capacitors and to the power inverter will always flow through the thermistor location.
As I mentioned in post #33, the integrity of the gate driver circuits is very important, if the inverter is going to work again, and if repeated failure of new IGBTs is to be avoided. Before installing any replacement power transistors you need to trace the gate wiring, from the IGBTs ( Pin 1 from the left ) back towards the Control board.
As @Jan-DIY suggested in post #9 of this thread
WWS200, Parweld XTS162 welder repairs
Hi Chaps, I recently bought a known faulty WWS200 MMA/lift rig welder. It doesn’t look as if it has even struck an arc as it is immaculate condition. The issue is that when plugged in the welder is completely dead. I only got it this afternoon so have only had chance to take a quick look...
www.mig-welding.co.uk
I have just acquired a broken Static Arc 200 inverter MIG. It has a green disc-shaped thermistor as the precharge resistor, same size as yours, marked "15P", bypassed by a timed relay. The cold resistance is 100 Ohms. This would equate to the cold resistance of a 40 watt mains filament bulb, so as suggested, that would work as a temporary substitute.
charlton1706
New Member
- Messages
- 24
- Location
- doncaster
Hi all I know it’s been a while I’ve been busy but here goes I got the new igbt’s fitted along with the capacitors and boom the welder springs to life lol but now the problem I’m having it will not arc the hf works but can’t seem to get a arc any ideas lol
Thank you for the update. According to this thread:
the power to run HF start comes from the main inverter, and this is confirmed by your block diagram in Post #23. That implies the inverter is working, but something is wrong with the control logic. It may not be ramping up the output current high enough to strike an arc. This is measured by a current-sense coil around one of the output wires.
From the block diagram, I would suggest that you locate the six output rectifier diodes, and check them.
Are you sure that the soft-start resistor is now getting bypassed correctly by the relay?
Do you get the same fault at all settings of the Mode switch ( HF TIG, Lift TIG, MMA ), and all positions of the current control?
What is the open-circuit output voltage ( should be 60 - 70v DC ), and does this voltage change when you try to strike an arc?
Hf Arc start board
I recently bought a tig hf arc start board from China but it came with absolutely no documentation what so ever. Not even marks on the on board interfaces. It is supposed to be a 220v hf board but I don’t know if it is powered with 220v and also have an “activating” interface that starts and...
www.mig-welding.co.uk
From the block diagram, I would suggest that you locate the six output rectifier diodes, and check them.
Are you sure that the soft-start resistor is now getting bypassed correctly by the relay?
Do you get the same fault at all settings of the Mode switch ( HF TIG, Lift TIG, MMA ), and all positions of the current control?
What is the open-circuit output voltage ( should be 60 - 70v DC ), and does this voltage change when you try to strike an arc?
