OH4Â Control Board Ambient Overheat fault in Toshiba drive
OH4 Control Board Ambient Overheat fault in Toshiba drive
Description While OH1 is Motor Heat and OH2 is Heatsink Heat, OH4 is the temperature of the Control Circuit Board itself. The main microprocessor has an on-die thermal sensor. If the air *inside* the drive casing (not the heatsink) gets too hot, the capacitors on the control board will dry out rapidly and logic gates may become unstable. OH4 trips to save the electronics from thermal death. Causes
1. Internal Stirring Fan Failure: Large drives often have a small internal fan just to circulate air over the circuit boards. If this fails, pockets of hot air develop.
2. Cabinet Ventilation: The drive is mounted in a sealed enclosure sitting in direct sunlight, turning the cabinet into an oven.
3. Clogged Vents: The small ventilation grills on the plastic front cover of the drive are blocked by dust.
4. Overloaded Regulator: Drawing too much current from the 24V terminals can cause the on-board power supply regulator to overheat. Solution Check the ambient temperature of the room or cabinet. If it is above 40°C or 50°C, you must install cabinet cooling (AC or filtered fans).
Inspect the drive's internal fans. On a G9 or AS3, remove the front cover and look for the small 40mm or 60mm fans mounted on the control chassis. Replace them if they are stopped or noisy.
Touch the control board components (carefully, with ESD protection). If the main linear regulator is scorching hot, disconnect any external sensors powered by the drive to see if the temperature drops. If the board overheats with no load and good ventilation, the board itself has a shorted component and needs replacement.
Description While OH1 is Motor Heat and OH2 is Heatsink Heat, OH4 is the temperature of the Control Circuit Board itself. The main microprocessor has an on-die thermal sensor. If the air *inside* the drive casing (not the heatsink) gets too hot, the capacitors on the control board will dry out rapidly and logic gates may become unstable. OH4 trips to save the electronics from thermal death. Causes
1. Internal Stirring Fan Failure: Large drives often have a small internal fan just to circulate air over the circuit boards. If this fails, pockets of hot air develop.
2. Cabinet Ventilation: The drive is mounted in a sealed enclosure sitting in direct sunlight, turning the cabinet into an oven.
3. Clogged Vents: The small ventilation grills on the plastic front cover of the drive are blocked by dust.
4. Overloaded Regulator: Drawing too much current from the 24V terminals can cause the on-board power supply regulator to overheat. Solution Check the ambient temperature of the room or cabinet. If it is above 40°C or 50°C, you must install cabinet cooling (AC or filtered fans).
Inspect the drive's internal fans. On a G9 or AS3, remove the front cover and look for the small 40mm or 60mm fans mounted on the control chassis. Replace them if they are stopped or noisy.
Touch the control board components (carefully, with ESD protection). If the main linear regulator is scorching hot, disconnect any external sensors powered by the drive to see if the temperature drops. If the board overheats with no load and good ventilation, the board itself has a shorted component and needs replacement.
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