Older microwave/convection oven I picked for free on Marketplace. Previous owner replaced turntable motor which didn't fit in the mounting hole properly. Shaft was at an angle causing plastic thing that fits onto it to eventually break. Filed the hole bigger, fitted the motor correctly, put on a new plastic thing, all (almost) is OK.
The fluorescent display is quite dim. The camera doesn't see what the eye sees so these pictures are brighter than what the display really looks like:
As you can see even from these pictures, the tops and bottoms of the letters are dimmer than the middle.
I did replace C20 as it checked low but no change. R10 and R11 look like they have generated quite a lot of heat but check at the proper 18 ohms. Pin 2 on IC-1 is specified as the Anode driver voltage of -40 volts. I have not cheked that voltage but I have checked Pin 29 of the display tube which is fed by Pin 2 through a 100k resistor. Pin 29 voltage to either the case or pin 31/32 or pin 1/2 of the display starts out at about -32 volts at power up of the microwave but then settles down at about -12 volts.
That seems low but that's about where I'm stuck, not being terribly familar with how fluorescent displays work. Is this display dying and in doing so pulling down the driver voltage from 32 to 12 as the display starts up?
Here's the schematic for reference if it helps:
Thanks in advance for any help. I would love to take this home and start "air frying" (the new name for convection cooking) but this probably isn't coming home if the display is this dim.
Val
The fluorescent display is quite dim. The camera doesn't see what the eye sees so these pictures are brighter than what the display really looks like:
As you can see even from these pictures, the tops and bottoms of the letters are dimmer than the middle.
I did replace C20 as it checked low but no change. R10 and R11 look like they have generated quite a lot of heat but check at the proper 18 ohms. Pin 2 on IC-1 is specified as the Anode driver voltage of -40 volts. I have not cheked that voltage but I have checked Pin 29 of the display tube which is fed by Pin 2 through a 100k resistor. Pin 29 voltage to either the case or pin 31/32 or pin 1/2 of the display starts out at about -32 volts at power up of the microwave but then settles down at about -12 volts.
That seems low but that's about where I'm stuck, not being terribly familar with how fluorescent displays work. Is this display dying and in doing so pulling down the driver voltage from 32 to 12 as the display starts up?
Here's the schematic for reference if it helps:
Thanks in advance for any help. I would love to take this home and start "air frying" (the new name for convection cooking) but this probably isn't coming home if the display is this dim.
Val
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