Nevermind for the last 2 questions, I had to discharge them. Just getting a little carried away. It's my time now to get this thing back together and everything is looking great so far. That is until testing time comes!
Okay, here are the results:
From closest to the terminal out to the 4th power supply mosfet, 12V through remote pulling .11A
Gate: 4.27V, 4.27V, -.26V, 3.57V
Drain: -.27V, -.27V, -.27V, -.27V
Source: 0V, 0V, 0V, 0V
From closest to the terminal out to the 4th power supply mosfet, 12V through remote pulling .11A
Gate: 4.27V, 4.27V, -.26V, 3.57V
Drain: -.27V, -.27V, -.27V, -.27V
Source: 0V, 0V, 0V, 0V
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The -.26V reading came from the transistor that got hot as hell when I tried powering it up after only changing the PS transistors.
The FET with the lower voltage on the gate is either shorted (likely) and/or could have a defective gate resistor.
Thank you for your response, so I checked the resistors, there's 2 near it and one reads 57 ohms and the other reads 7K ohms. So I don't think it's a bad resistor. The only other thing is that it's shorted like you said. I honestly wouldn't even know where to begin, I don't think these are double layer pcb's, there are likely other planes. How would I even start to troubleshoot this?
A gate resistor shouldn't read 7k ohms. The short would be between the terminals of the FET (if there is a short).
What are the markings on the gate resistor reading 7k?
What are the markings on the gate resistor reading 7k?
The markings are 1502 and it is R1008. But I just tested pins 1 and 2 on the transistor and it is shorted. I have plenty of extras, so I'm gonna change it real quick and get back to you. . .
Ok ,I hope you're still there, here are the voltages:
Same format as before:
G: 4.36V, 4.36V, 4.9V, 4.9V
D: -.16V, -.16V, -.16V, -.16V
S: 0V, 0V, 0V, 0V
So am I good to go? !
Same format as before:
G: 4.36V, 4.36V, 4.9V, 4.9V
D: -.16V, -.16V, -.16V, -.16V
S: 0V, 0V, 0V, 0V
So am I good to go? !
That was a brand new transistor that was shorted. I just checked all of my new ones and one other that I never even used was shorted! That is why I didn't even think to check the transistor for a short b/c it was brand new. I figured somewhere down the line a short was being caused.
Where did you buy them?
Static electricity 'can' cause the gate to short but it's not common for the types of FETs used in power supplies.
Static electricity 'can' cause the gate to short but it's not common for the types of FETs used in power supplies.
digi-key. . ., yea, I feel duped. What is the next step? Do I connect the B+ now?
Yes, I know about static, but I have never ever had that happen before.
Yes, I know about static, but I have never ever had that happen before.
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If you purchased from digi-key, the fault is almost certainly due to improper handling after you received them.
If you read the same on all gate legs of the power supply FETs, the drive circuit is likely OK.
Did you check the output transistors to confirm that none were shorted?
When you apply B+, all heatsink mounted components must be clamped tightly to the heatsink and you need to have a low value fuse (10 amps) of a current limiter inline.
If you read the same on all gate legs of the power supply FETs, the drive circuit is likely OK.
Did you check the output transistors to confirm that none were shorted?
When you apply B+, all heatsink mounted components must be clamped tightly to the heatsink and you need to have a low value fuse (10 amps) of a current limiter inline.
According to my readings, there is some small difference in some of the transistors. Is this ok? 4.36 and 4.9V on the gates of those two pairs. Also, the drain is supposed to be negative?
If you're referring to the output transistors, as long as you don't read anything near 0 ohms between the legs of any individual transistor, they're likely OK.
I was talking about the power transistors there is a small variation in the gate pairs.
'Power transistors' covers virtually all large transistors. That's not the same as 'power supply transistors'.
Without knowing precisely how you're testing, there's no way to know if that's significant.
Without knowing precisely how you're testing, there's no way to know if that's significant.
Oh, I'm sorry, I was talking about the power supply transistors the whole time, except for when I said output transistors.
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