MS2931 going into protection
Posted: January 29th, 2017, 7:27 pm
As the title states, I have an MS2931 going into shutdown immediately after power up.
No neck glow and no HV. Potting compound on H.Drive coil had leaked, but I removed the HOT, coil, and FBT and cleaned that up. With FBT and F701 removed, and HOT/coil installed, I've wired a lamp holder to the metal frame and PSU side of F701; 75W bulb does light up for a second or two.
HOT tests fine out of circuit.
R511 replaced since it had come into contact with the potting compound.
B+ is steady around 183VDC.
Vertical IC was replaced, showing 15VDC on pin 7, and 15VDC on pin 4; pins 5/6 show nothing (not sure if this is normal, absent an input signal), but I do read -15VDC from T901.
U921/U922/U602 are outputting steady 12VDC/5VDC/9VDC.
U951 pin 6 and U351 pin 26 both stay low; VCC reads 12VDC and 5VDC, respectively.
U901 pin 10 reads about 26VDC, and pin 7 reads 5V after shut down.
Heater reads around -10 to -11VDC, and even after 30 minutes the heater circuit hasn't drained. not sure if this is normal.
Haven't pulled Q901 and checked that, but I figured if all of my output voltages were good I shouldn't need to?
Not sure what to check, now. Any suggestions?
No neck glow and no HV. Potting compound on H.Drive coil had leaked, but I removed the HOT, coil, and FBT and cleaned that up. With FBT and F701 removed, and HOT/coil installed, I've wired a lamp holder to the metal frame and PSU side of F701; 75W bulb does light up for a second or two.
HOT tests fine out of circuit.
R511 replaced since it had come into contact with the potting compound.
B+ is steady around 183VDC.
Vertical IC was replaced, showing 15VDC on pin 7, and 15VDC on pin 4; pins 5/6 show nothing (not sure if this is normal, absent an input signal), but I do read -15VDC from T901.
U921/U922/U602 are outputting steady 12VDC/5VDC/9VDC.
U951 pin 6 and U351 pin 26 both stay low; VCC reads 12VDC and 5VDC, respectively.
U901 pin 10 reads about 26VDC, and pin 7 reads 5V after shut down.
Heater reads around -10 to -11VDC, and even after 30 minutes the heater circuit hasn't drained. not sure if this is normal.
Haven't pulled Q901 and checked that, but I figured if all of my output voltages were good I shouldn't need to?
Not sure what to check, now. Any suggestions?