Hello guys,
I received some logic controller units to repair from boilers. All of them with problems on SMPS circuit, all of them solved except one.
On this one I can´t undestand the problem why power supply doesn´t work. I found the PWM IC (VIPer22A) destroyed and main filter capacitor at primary damaged also. After replacing them the unit didn´t work. I check all components in primary and secondary side, all of them correct.
To find the problem I replaced all primary components including transformator by known good components from another unit which worked properly, in fact all components had same values testing them with multimeter but as the power supply was not switching I took that way to solve it.
After replacing all components power supply didn´t switch on!!! I connect my power supplies to secondary side to see behavieur after secondary side, +5V, +12V and -12V, and unit worked properly.
If you check the drawing I made you can see it´s a really simple SMPS, where I didn´t put LC filter and NTC, directly AC on bridge. I have 310Vdc at drain from VIPer22A but it never switches not even for a second.
http://www.restoretronic.com/descargas/Esquema primario fuente de alimentacion.jpg
**broken link removed** dañado en SN0235.jpg
I have no answer about why PWM IC don´t start up with the high voltage there. I also tested the pin number 1 and 2 are connected to main groung at diode bridge.
May be one of you have some good idea...