Presonus Eris E8

[Sender]

My friend's monitor is broken and I'm looking at it for him. It looks like one of the rectifiers on the power supply broke. I poked around a bit and didn't seen anything else wrong, however I'm hoping a schematic is kicking around somewhere so I can double check. Does anyone have an Eris E8 schematic they can share, or any other advice (maybe you fixed a similar issue with your E8)?

 

[Khron]

List of symptoms? Some internal photos? Perhaps voltage measurements?

This is GroupDIY, remember? Sitting around waiting for miracles... isn't the most productive option ;D

 

[Sender]

I was hoping the schematic would help with the DIY portion of it, it usually does!!!

When the monitors are switched on they immediately pop the input fuse. I cracked it open and didn't seen anything immediately obvious (no swelled caps, burnt components, etc.). It looks like there are two center-tapped secondaries that come off the transformer and go to rectifiers. The AC inputs of one of the rectifiers was shorted together so I'm going to replace that.

It seems a little odd that that is the only thing broken. I would expect something down stream to also be broken but I checked across all the big filter caps and LDOs and there weren't any shorts there.

I'll replace the rectifier and see how that changes things.

 

[Khron]

One thing to check might've been to disconnect the secondaries and see if it still popped fuses.

Although a "series bulb tester" might be a good way to save on fuses, for testing purposes.

Did you measure that "short" across the rectifier AC input with the transformer still connected, or...?

 

[JohnRoberts]

Check for a shorted reservoir cap... a bad cap can eat the diodes, while a shorted diode can trash the caps, so a bit of a chicken/egg thing.

JR 

 

[Sender]

One thing to check might've been to disconnect the secondaries and see if it still popped fuses.

Although a "series bulb tester" might be a good way to save on fuses, for testing purposes.

Did you measure that "short" across the rectifier AC input with the transformer still connected, or...?

All measurements were made with the AC input transformer disconnected.

 

[Khron]

Then yes, at least two diodes in the respective bridge had turned into wires.

I'm guessing one (higher-voltage) secondary's for the power amps (or at least the woofer), and the other's for the opamps (and maybe tweeter amp)? Which one was shorted?

 

[Sender]

For those that were curious (and I'm sure so many were) there was a small ceramic cap across the diode bridge input that was shorted. Simply replacing that took care of the issue!

 

[Khron]

There you go then ;D

I've revived several laptops with that exact problem (shorted ceramic cap)...