The replacement TVS diode arrived today and I soldered it on. The short circuit observed before is gone. I plugged it into my truck and the GAUGE fuse didn't blow and now I have A/C again. I fixed the issue finally. Thank you @george_tlc for your help in identifying the part. It was the correct...
I do think the "27 620" markings on the TVS diode means 27V avalanche, 620W. Doing the math, this part would burn out if it had to shunt more than 24A at 27V. That's three times the capacity of the 7.5 Amp GAUGE fuse that protects the circuit. I wonder if that also means if the Amps stay under...
I hope you're right. Given the markings, will you help me find a replacement part? It sounds like the zener diode symbol on the board sent me in the wrong direction.
It can't be 6.2V zener voltage. The input to the cathode on this part is straight from the GAUGE fuse, so 12-14V. If the zener voltage is 27V then it wouldn't ever kick in as a voltage regulator. I have no clue what the specs are on this part. The only way to really know is for somebody with a...
Based on the markings on the circuit board and the fact that the cathode is connected to hot, I'm 99% sure that this is a zener diode used to provide a reference voltage for this part of the circuit.
The next question is, based on the markings on the diode, what are its specifications so that...
So to be clear, the failed part is a diode which regulates power and is also a common point of failure in electronics. If you ever have a spinning hard disk die because the platters fail to spin up, a quick trick is to find the power diode and desolder it to remove the short circuit. The drive...
Here's the photo from before desoldering the capacitor and the diode.I'm testing the same points on the board as I did in the "after" shot above.
I just wanted to show that there was a short before desoldering and then there isn't one after desoldering the capacitor and diode.
aaaaand, of course just after a I order the new part and spend the hefty amount of money, I followed the hot traces to the second board and found a hefty diode that was next in the circuit. I desoldered it and sure enough it was actually the short:
It's hard to take pictures and test parts at...
Well, s***. Now that the sun is up and nap time is over, I decided to dive in deeper. One thing I forgot to mention last night is that there is no guarantee that the first filtering cap is the short. I got ahead of myself late last night. In theory, anything on this board could be shorting, its...
But it turns out there is a hidden and undocumented splice that changes this:
J4, 10 - C16, 4 cooling fan, also A/C Air Amplifier and two other places I haven't followed the wires to yet.
Oh, you're right, it is pin 10. I just took a closer look at the note on page 5 of the EWD. I was looking at the arrows and not the numbers in the note :cheers:
So it is pin 10. It really doesn't matter though because the junctions label all pins as "A" or "B" and so knowing the pin number...
If any of you guys are ever in Vegas, you should stop by the Las Vegas hacker space called The Syn Shop. I learned this electronics theory from playing around with circuits on nights where everybody solders up some electronics kits.
The proper fix of course is to replace the capacitor with a new one with the same capacitance and voltage tolerances. Here's a closeup of the markings on the capacitor:
So this is a 47 uF 35V tolerant electrolytic capacitor. It's likely an aluminum one but the inner material doesn't really...