Really dumb question about fuses, ratings. Still blowing fuses

[fastline]

Unless it is under that glob of mystery glue on that other daughter board (dont think so), no, there is no optocoupler. I can get a pic of that other daughter board but It does not look like the dimensions work to be an optocoupler. Only other chip on the boars is a 084C towards the output side.

 

[ben7]

Is there a resistor and capacitor connected in series directly to the secondary of the transformer?

 

[fastline]

Well, that gets a bit confusing because there is a total of 14 taps on the transformer. 7 on the primary, and 7 on the secondary. Of the ones on the secondary, 2 of them go to those large diodes to the side of the transformer, 1 goes to a pair of small diodes in series, then some SM resistors and such and eventually to the 2 regulators in TO-220 packages, 1 goes to R52, then to the threaded brass mount on the back (common or ground?), 1 goes to the the second largest cap and R63-R65 and make their to that lonely transistor closest to that other daughter board.

I am not sure what exactly you are looking for but I can trace one of the secondaries from the tap through a cap and to some small surface mount stuff and into that other daughter board. Let me know what specifically you are looking for and I will take a look. I still want to know what is under that glob of glue but I fear I will destroy that board trying to find out.

 

[fastline]

Just for reference, without those PS mosfets on the board, I am able to apply power without any current draw at all and I do here something "spooling up". Sounds a lot like a camera flash but MUCH quieter. Actually can barely hear it. I think it is the main cap charging up. Not if that is helpful at all.

 

[ben7]

There has to be a feedback circuit in there some where. Are you sure everything tested fine?(no shorts, open circuits, etc) I haven't encountered an smps transformer that was shorted out.

 

[Nigel Goodwin]

There has to be a feedback circuit in there some where. Are you sure everything tested fine?(no shorts, open circuits, etc) I haven't encountered an smps transformer that was shorted out.

It happens, but it's really VERY rare - on the odd occasions it does happen, you'll almost certainly see a fair few of exactly the same transformer fail in the same way, presumably it's not been made correctly.