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Registered Member #1845
Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211
The cause of a hot regulator is usually a short between its center pin (ground) and pin3 (the regulated output voltage)
There are a couple things that might be causing this....
If you have your display board connected into the terminal on the circuit board backwards, it could be shorting the regulators out. (the display board is connected with that ribbon cable) It has to be oriented the correct way.
The capacitors could possibly be bad or a diode could be shorted out.
If you put in a new integrated circuit somewhere, and then suddenly noticed the regulators got hot, the integrated circuit could be bad, installed backwards, etc., and this could be shorting out the regulator.
Registered Member #1828
Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55
Well I trashed U62 getting it out. Put a new one in, and same result~1.7v. Pulled all the IC's and now have 15v. Started putting them in 1 at a time and checking U62. Bad U4. I now have it putting out a signal on gate when I apply 5v to ext mod. but can't get anything that means anything to me on the differential measurement. That's enough for today. I was hoping for sparks for christmas. Maybe tomorrow.
Registered Member #1845
Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211
Well I trashed U62 getting it out. Put a new one in, and same result~1.7v. Pulled all the IC's and now have 15v. Started putting them in 1 at a time and checking U62.
The wild goose chase begins (guns go off in the background)
I did what you are doing numerous times also. Stick with it though. Good luck.
I now have it putting out a signal on gate when I apply 5v to ext mod. but can't get anything that means anything to me on the differential measurement.
you should be able to see the +30v -30v swings on each IGBT. Have you figured out how to do this with your oscilloscope.
Registered Member #1589
Joined: Sun Jul 13 2008, 06:40PM
Location:
Posts: 70
If I am not mistaken, I have a very similar model of scope, and it does not have internal ground isolation. Do a continuity test between the case of the scope and mains ground. If it should show to be connected, look into making an isolation transformer and try again.
Edit: Take two matching transformers. ie two 120V to 12VAC transformers, connect the two 12V secondaries together, connect mains to one 120V, and the scope to the other transformer's 120V. Make sure one side of the second transformer's 120V is not grounded. Someone help me out with this explanation if it is not sufficient.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
For your scope and differential measurements . . .
1. Set Ch1 / Ch2 to ADD 2. Set Ch2 to INVERT (button) 3. Ensure both channels set to the same voltage scale 4. Tie ground leads together (but don't attach to anything) 5. Each probe goes to the points you are measuring.
Registered Member #1828
Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55
OK, I got a squarewave signal on E to C on each IGBT. Is that all I need? A better 9V battery probably helped.
Adjusted Overcurrent Check Adjust R30 to halfway, ok 10k, 10 turn pot, rotate to stop, backup 5 turns. 1,2~11! Plan b go to back of board and set to 5K Check Overcurrent setpoint Check
Dang, I have to finish the front panel to mount the led's
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
d20180 wrote ...
OK, I got a squarewave signal on E to C on each IGBT. Is that all I need? A better 9V battery probably helped.
What measurements are you trying to check? If you are checking the gate driver, you are measuring the wrong points. You should be getting a +30V to -30V square wave signal on the Gate to Emitter of each IGBT when checking gate drive. Also, after you verify each gate individiually, you should then put your oscilloscope back into regular 2-channel operation and then just touch the probe of each channel (don't connect the probe GND to anything!) to each IGBT's gate and verify that the signals are out of phase from one another.
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Help needed with MiniBrute
