Hi all,
I bought a 300W 12/200 modified sine wave inverter for my van, but it starts beeping and goes off when trying to manage about 100W. I opened a dispute, and seller sends me a working unit (not the same board), but still want to repair the first one.
I tryed testing it with a 60W light and everithing looks ok, but if I switch on another one, The inverter starts beeping, alarm led switches on, and both lights go off.
I don't have much experience, but taked a look arround and everithing looks ok... checked mosfet and they look ok too, no capacitors conducing, etc..
Finally, I decided to make some inverse engineering on 12v stage. It has KA7500B controller managing two mosfet and in charge of triggering the alarm. The error is triggered by a small circuit, left-hand side of the buzzer, two zener diodes a npn transistor and some other simple components, connected to pin 1 of KA7500B, it is, if I'm not wrong, an error comparator pin (pins 1-2 and 15-16 in the KA7500B)
When alarm triggers, N13 transistor starts conducing and I can see about 4v at it's Emitter pin (B).
Measuring transistor's base with a cheap oscilloscope, switching on a 220V 60W ligth I can see a lot of noise, and when the second test light was switched on and the inverter goes off the noise stops as shown in the image:
Transformer also warms up, may it be making noise and that noise triggers the transistor?
Thanks in advance.
I bought a 300W 12/200 modified sine wave inverter for my van, but it starts beeping and goes off when trying to manage about 100W. I opened a dispute, and seller sends me a working unit (not the same board), but still want to repair the first one.
I tryed testing it with a 60W light and everithing looks ok, but if I switch on another one, The inverter starts beeping, alarm led switches on, and both lights go off.
I don't have much experience, but taked a look arround and everithing looks ok... checked mosfet and they look ok too, no capacitors conducing, etc..
Finally, I decided to make some inverse engineering on 12v stage. It has KA7500B controller managing two mosfet and in charge of triggering the alarm. The error is triggered by a small circuit, left-hand side of the buzzer, two zener diodes a npn transistor and some other simple components, connected to pin 1 of KA7500B, it is, if I'm not wrong, an error comparator pin (pins 1-2 and 15-16 in the KA7500B)
When alarm triggers, N13 transistor starts conducing and I can see about 4v at it's Emitter pin (B).
Measuring transistor's base with a cheap oscilloscope, switching on a 220V 60W ligth I can see a lot of noise, and when the second test light was switched on and the inverter goes off the noise stops as shown in the image:
Transformer also warms up, may it be making noise and that noise triggers the transistor?
Thanks in advance.