- Thread starter steveuk
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In the partial diagram that you posted on Friday, there is a component marked "X". It has a symbol like a resistor, it is in a high-current path ( thick lines on the diagram ), and it has "thin" wires at each end. I assume it is a current-measuring shunt. It is probable that the control PCB expects to see a voltage ( a few millivolts ) across this shunt, and the PCB then adjusts the phase control firing angle for the thyristors to get the desired current regulation.
When troubleshooting the PCB on your "workbench simulator", have you taken into account the need for feedback from this shunt?
When troubleshooting the PCB on your "workbench simulator", have you taken into account the need for feedback from this shunt?
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Ok, Great reactivity, Yes sure i am aware about the shunt feedback, i inject 50mA into the pin 2 and 3 of the board and the UA741 starts to give a good response.
About the figure that i posted on last Friday it is a resistor not a shunt, the shunt has 4 connections. when it is covered by a electrical current it gives through the 2 pins the image by mV.
Thanks Eddie
About the figure that i posted on last Friday it is a resistor not a shunt, the shunt has 4 connections. when it is covered by a electrical current it gives through the 2 pins the image by mV.
Thanks Eddie
slim_boy_fat
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I can see his video here, does this help you see it?
https://www.youtube.com/watch?time_continue=40&v=ZNfFWwnFLTI
Good morning Sirs,
Is still somebody on this argument, because i am tring to repair the electronic board the 20801. 9.800 for the Mosa ts180 d el. My idea is problem on lm348 / lm741 because at the 3 pins of the tca785 no correct voltage is driven. All tips welcome also schematich diagram too.
Is still somebody on this argument, because i am tring to repair the electronic board the 20801. 9.800 for the Mosa ts180 d el. My idea is problem on lm348 / lm741 because at the 3 pins of the tca785 no correct voltage is driven. All tips welcome also schematich diagram too.
Hello and welcome to the Forum!
There have not been any updates to this thread for 4 years. It is not clear what, if any, was the outcome of the previous solution; the YouTube video does not contain any clues.
What is the actual problem with your engine-driven welder? Does it always run at full power? Have you checked the power semiconductors ( diodes and thyristors ) in the controlled bridge rectifier for shorts? Do you see gate pulses on the thyristor gates or at the pulse transformer primaries?
The diagram in Post #30 was hand-drawn, presumably from viewing the wiring on the actual machine. If you are comparing it to an official wiring diagram, then it is likely that the published diagram is correct. How does the wiring look on your machine?
Referring to the "3 pins of the TCA785", I assume you mean there is no signal at each of the three TCA785 chips? [Three chips are used to provide 3-phase control.] Do you mean the control input or the pulse output pins?
You may find this TCA785 application video helpful:
There have not been any updates to this thread for 4 years. It is not clear what, if any, was the outcome of the previous solution; the YouTube video does not contain any clues.
What is the actual problem with your engine-driven welder? Does it always run at full power? Have you checked the power semiconductors ( diodes and thyristors ) in the controlled bridge rectifier for shorts? Do you see gate pulses on the thyristor gates or at the pulse transformer primaries?
The diagram in Post #30 was hand-drawn, presumably from viewing the wiring on the actual machine. If you are comparing it to an official wiring diagram, then it is likely that the published diagram is correct. How does the wiring look on your machine?
Referring to the "3 pins of the TCA785", I assume you mean there is no signal at each of the three TCA785 chips? [Three chips are used to provide 3-phase control.] Do you mean the control input or the pulse output pins?
You may find this TCA785 application video helpful:
Hallo Eddie49,
Thanks a lot for your answer, excuse for my bad english.
The situation is this:
The diesel works the generator too, infact there are the 3 phase 400, the monophase 230 Vac and the 3phase 45 Vac for welding section.The throttle is manual. At the welding electrode no voltage present. The rectifier is ok. The power supply on the electronic board +- 15VDC present, but no gates signal present. I found two of three 470 ohm 10W, broken. Before trying the board on the system, I am check the board at desk. No correct voltage ,-14VDC, at the 3 pins (pin 11 of TCA875 control voltage). If i supply from external, a variable voltage as requested from the TCAs, then i have signal gates, so do you have schematic diagram because it not clear to me the section of lm348 and lm 741 how the system controls the current the voltage.
Thanks for your attention
Massimo
Thanks a lot for your answer, excuse for my bad english.
The situation is this:
The diesel works the generator too, infact there are the 3 phase 400, the monophase 230 Vac and the 3phase 45 Vac for welding section.The throttle is manual. At the welding electrode no voltage present. The rectifier is ok. The power supply on the electronic board +- 15VDC present, but no gates signal present. I found two of three 470 ohm 10W, broken. Before trying the board on the system, I am check the board at desk. No correct voltage ,-14VDC, at the 3 pins (pin 11 of TCA875 control voltage). If i supply from external, a variable voltage as requested from the TCAs, then i have signal gates, so do you have schematic diagram because it not clear to me the section of lm348 and lm 741 how the system controls the current the voltage.
Thanks for your attention
Massimo
