2PAC Mafia
Member
Hi,
I´m trying to repair an Eltek fire alarm unit controller. There is no communication between the display unit and the other unit where all sensors are connected.
I have not experience on this unit but checking the power supply where I should get 24V I´m getting 30V so I´m thinking about the possibility of having problems at power supply and due to that the system is blocked, detecting to high voltage value (it is only an idea).
The main IC from the SMPS is an UCC3804. I have checked the feedback pin is ground connected and at Comp pin I have 1,24V. I tell you this because I thought about the possibility of having some problem at feedback circuit getting the maximum output voltage at SMPS. The Comp pin is connected to the transistor part from a HCPL354 opto at collector and emitter directly to ground. In theory, that should control the stability output at power supply.
I replaced the opto swapping with another on the board. Same behavieur. Measuring at pin 6 I have 45,8KHz PWM pulse.
Any idea why do I have this high voltage output? I think that is not normal. As always not schematics available.
Can I play with Comp pin (with a resistor) just trying to change the output?
I attach some manual I found in Internet just to show you what I´m speaking about.
I´m trying to repair an Eltek fire alarm unit controller. There is no communication between the display unit and the other unit where all sensors are connected.
I have not experience on this unit but checking the power supply where I should get 24V I´m getting 30V so I´m thinking about the possibility of having problems at power supply and due to that the system is blocked, detecting to high voltage value (it is only an idea).
The main IC from the SMPS is an UCC3804. I have checked the feedback pin is ground connected and at Comp pin I have 1,24V. I tell you this because I thought about the possibility of having some problem at feedback circuit getting the maximum output voltage at SMPS. The Comp pin is connected to the transistor part from a HCPL354 opto at collector and emitter directly to ground. In theory, that should control the stability output at power supply.
I replaced the opto swapping with another on the board. Same behavieur. Measuring at pin 6 I have 45,8KHz PWM pulse.
Any idea why do I have this high voltage output? I think that is not normal. As always not schematics available.
Can I play with Comp pin (with a resistor) just trying to change the output?
I attach some manual I found in Internet just to show you what I´m speaking about.