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Registered Member #3964
Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332
My opinion is that there must be an floating pin, or looks soldered properly but not. also, i would like to ask, is there a paralleled input on the pin 1? also, how do you treat those ICs? they are CMOS that are very very sensitive on static charges. so make sure that when you try to hold the pins, you are grounded - because we might have statics on our body unconsciously.
Registered Member #6038
Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248
Thanks everyone for the suggestions. I will go back and check the solder joints again and see if anything is floating that I overlooked. Will also start looking downstream of the output too for something that has blown - things just stopped working so a blown component sound logical.
Thanks again - will update with what I find later today.
Registered Member #6038
Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248
At LAST !!! 2 of the 74HC14's were damaged. The one was completely fried and produced a flat 5v output regardless of input. The other one was giving that weird 1.8v offset but with the square wave out. So I tried a 3rd one and bingo! I guess they are really sensitive.
During testing after I hooked up the half-bridge power board, I noticed that with a 100Hz modulator signal my GDT "sings". I don't recall it doing that before. The waveform at the gates of the MOSFETs is not good either. Suspect that the MOSTFET(s) may be toast too which is causing the singing due to the load - agree with this diagnosis? GDT Singing is bad right?
Registered Member #6038
Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248
I have been super careful with the handling - running low on them
Good to know about the singing GDT - Driver output to the GDT is now good, but I need to test the MOSFETs as the waveform at the gates are a disaster. Could explain the weak spark output too. Will take the half-bridge apart and see what's up. This has been a great learning opportunity. Hopefully the thread will be useful to others in the future.
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