Hi,
I have a dead coffee machine that I would like to fix. After some probing, I have found the power supply to be faulty. Problem is, I have no schematics or information I can reference.
It looks like a SMPS built around a DM0265 controller. It has a transformer without any markings that makes it quite hard.
Anyway, the transformer has 4 windings around a common core. The primary had 120 windings, the next on top of that had 15, next there was 9 and finally 17. The 15 wind coil was connected to VDD on the DM0265 and nothing else.
The other two where connected to the rest of the logic. The start (or end) of the 9 turn was VSS for the board as I traced a few tracks. The other side of the winding was joint to the start of the 17 turn winding. This junction went to a L7805 and the end of the winding was connected to the rest of the circuit. (See attached drawing)
I need to know what the expected output voltages would of been. I guess the output going to the L7805 would not matter too much as long as it is less then the max of the vreg as it does not go anywhere else. The other tap went to stepper motors so it could be anything..
What I do know is:
As this is more of a exercise it trying to learn, I would like to workout what the output voltages would of been. I will then see if I can find a replacement transformer or wind mine own.
So, can anyone help me work this out?
The other thing I don't understand is why this failed. When I pulled the transformer out and checked the windings I did not find any broken or shorted winding but when I applied power it got hot (too hot to touch) and I did see quite a bit of blackening on the board around it.
Thanks
I have a dead coffee machine that I would like to fix. After some probing, I have found the power supply to be faulty. Problem is, I have no schematics or information I can reference.
It looks like a SMPS built around a DM0265 controller. It has a transformer without any markings that makes it quite hard.
Anyway, the transformer has 4 windings around a common core. The primary had 120 windings, the next on top of that had 15, next there was 9 and finally 17. The 15 wind coil was connected to VDD on the DM0265 and nothing else.
The other two where connected to the rest of the logic. The start (or end) of the 9 turn was VSS for the board as I traced a few tracks. The other side of the winding was joint to the start of the 17 turn winding. This junction went to a L7805 and the end of the winding was connected to the rest of the circuit. (See attached drawing)
I need to know what the expected output voltages would of been. I guess the output going to the L7805 would not matter too much as long as it is less then the max of the vreg as it does not go anywhere else. The other tap went to stepper motors so it could be anything..
What I do know is:
- The controller worked at a frequency of 67KHz.
- The transformer had a surface area of 49mm squared and made form the black ceramic like material.
- The voltage on the stepper motor controllers is between 10 and 46v.
- Input voltage to the transformer was ~300 DC.
As this is more of a exercise it trying to learn, I would like to workout what the output voltages would of been. I will then see if I can find a replacement transformer or wind mine own.
So, can anyone help me work this out?
The other thing I don't understand is why this failed. When I pulled the transformer out and checked the windings I did not find any broken or shorted winding but when I applied power it got hot (too hot to touch) and I did see quite a bit of blackening on the board around it.
Thanks