Friends you can see I have a PCB here it has got powered on we will check its voltages when we check its normal voltages its 314 volts passing through it on its positive side now will check voltages on its u v w 74 volts are passing through it here as well 74 volts are passing through the third one is also 74 volts it means we should have here 15 volts which are not available so let me tell you what is it doing now see what will happen we will have to wait see the compressor started vibrated and stopped Now again…… see it starts and vibrates and stops it tries for 5 to 6 times and then totally stops starts again it's working the same way nowhere it will try to start once again now if we see the analyzer all the IGBTs are getting on but after that, they get switched off it means that its IPM is ok so where is the problem so then we over here it tries again and stops and its low side is preparing voltages but here one thing is faulty due to which this problem is coming if we check low voltages ang its 5, 6 and 7 number pin it is high input the high input means where positive voltages appear now here we have open indoor and now its outdoor PCB has start so it is started so we will check its voltages so when we have check its PCB voltages so how many voltages are coming here 322.5 volts are coming and here 78 volts are coming here also 78 volts are coming and here also 78 volts as its showing 78 volts and after som time its position changes but here as you can see volts are not coming here but after some time voltages will appear here as you can see so voltages has start coming here so 2.4 volts are coming here so our analyzer has also start working as you can see and all IGPTS has started and beside it compressor has also start working now we will check how many voltages are ccoming in next point so here 2.4 volts are coming we will also check in next points so in all points same voltages are coming which is totally fine and analyzer is also fine and compressor is also fine so it means that this PCB has get fine now here we have to understand one thing that designs of different PCBs are different diiferent companies use different techniques for PCBs so the design used in this PCB is that the voltages from direct micro controller that comes in to the IPM and IPM is directly controlled by some resistance and capacitors so protection is kept between micro controller otherwise no kind of half bridge IGPT driver is not installed here so see what we have done in it so as you can see what we have done in this PCB as we have changed IPM beside it ……IPM has also created problems in its low side so what problem was in its low side …….
I will show it to you as you can see as you can see its low side it consists of three points this 5, 6, and 7 number pin so high positive volts come in this 5, 6, and 7 number pin so here from 2.7 to 5 volts are coming directly from a microcontroller beside its 12 number pin it is for negative point when they get on and off then IGPTS also get on and off but what happened here that its resistance here so its is resistance R 84 beside it capacitor with it is C72 so when we were checking them with meter they were fine but when we were putting them in unit but as the unit was not working as we showed you but its resistance was getting high very fastly as i closed the unit than i cecked there values so its resistance was getting very high due to which IPM was not able to start and not able to start the compressor that's why I changed these three capacitors and resistance so now as you can see compressor has started working