Sorry, I thought I hadn't posted it in the right section. Should I delete one of them?
No it's ok, you can't delete threads
Why do you suspect this ic is bad? What voltages etc. have you checked so far? Check that you have voltage ACROSS the main filter cap (165vdc)
See the pdf, the output should drive a mosfet's gate, There will be a resistor from the mosfet source to ground, check that it is not open, it should be around 1Ω or less If it IS open the mosfet is likely shorted, if it is ok then I suspect the problem is elsewhere.
No it's ok, you can't delete threads
Why do you suspect this ic is bad? What voltages etc. have you checked so far? Check that you have voltage ACROSS the main filter cap (165vdc)
See the pdf, the output should drive a mosfet's gate, There will be a resistor from the mosfet source to ground, check that it is not open, it should be around 1Ω or less If it IS open the mosfet is likely shorted, if it is ok then I suspect the problem is elsewhere.
Hello R_J!
Across the filter cap I am getting 166V.
I am getting 12V on the VCC pin (pin 5) and 0 on the output (pin 6). Where is the source pin? Do you mean CS pin 4?
You would need to provide pictures of both sides of the circuit board to start troubleshooting.
12v on the vcc pin is good You would need a scope to see what is on the out pin for drive. The out pin should connect to a mosfet gate. This ic can not drive the transformer directly.
The source pin is on the mosfet, the CS pin will connect to it via a resistor.
You would need to provide pictures of both sides of the circuit board to start troubleshooting.
12v on the vcc pin is good You would need a scope to see what is on the out pin for drive. The out pin should connect to a mosfet gate. This ic can not drive the transformer directly.
The source pin is on the mosfet, the CS pin will connect to it via a resistor.
Hello RJ,
Tried to take pictures, on one side the one in the picture there was a lots of white hard glue that I had to remove. I discovered under the glue a damaged RS1M diode and since I didn't have a RS1M I replaced it with an FR107 diode. You're right, the out pin connects to a mosfet gate, as you will see in the photo (i removed the mosfet and C6, which I will replace), but I have 0V at the output of the mosfet. Here is a photo with some explanations. Tks!
Also, not much purpose on taking a photo of the other side, it is filled with glue and you see absolutely nothing. I would have to remove all that glue and it is a mess. Here is a photo anyways.
The transformer primary is connected between the + of the bridge rectifier and the mosfet drain, there should also be a feedback winding that supplies run vcc voltage for the ic. One end of the feedback winding connects to hot ground the other feeds a diode and then pin5 of the ic
Did you check the feedback circuit? You did check to make sure there was no shorted output on the secondary side, like shorted cable, shorted output diode etc.
The feedback is a winding off the transformer, (T1B) which connects to R4, and D1 diode to supply the run vcc for the ic. Your component designations will be different but the circuit should be the same.
Ok, so I checked every component on the back of the board and didn't find anything suspicous, except for a T4 diode that was in parallel with a 100 ohm resistor, so I removed it and it tested good.
Took out the little transformer and the output seems shorted as can be seen in the photos with my blue ring tester compared to a good coil. Also took a closup of the inside for your info.
I guess this means I will have to retire this power supply and keep it for parts with the exception of the transformer, right?
I doubt the transformer is bad, Check the resistance of the windings, if they are not open I suspect the transformer is ok. Did you check the primary and feedback windings with your ringer?
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