IEC-320 Filtered AC Inlet with open Neutral

[nevetslab]

This past month one of our Aguilar DB751A Bass Amps came over with the note on the front panel NOT POWERING UP. I moved it to the bench, removed the top cover and checked the 35A Bridge Rectifier, as those are known to fail from time to time. It was fine.

I plugged it into my Variac/Power Analyzer and brought up the AC mains, watching the current meter, seeing nothing change. Power Switch was fine and in the ON Position. Fuse was fine. I looked from the male pins of the IEC connector to the fuse holder, that was fine, and from the fuse holder to the power switch, that was fine. Checked the in-rush Thermistor on the barrier strip above the enormous Toroidal Power Xfmr, and that was fine. But, I had no continuity between the IEC Neutral terminal to the Power Switch. I removed the Filtered Corcom 15RB1-Z IEC Connector from the chassis, unplugged it, and sure enough, no continuity between the IEC inlet Neutral pin and the 1/4" Faston terminal on the back side.

NG_CD_15SRB1-Z_0-686076.pdf

I looked at the data sheet, not finding any in-line fuse. I unsoldered the Faston male terminal on the Neutral, which only resulted in melting the plastic housing around it, applying fresh solder while it was hot. That didn't change anything.

What an ODD Failure. Never seen anything like this fail before.

[Jon Snell]

I expect one side of the common mode choke has failed. These are only rated at 6Amps (C14) so many high peak current draw at switch on has proved too much for the poor filter.
Crown use a larger connector (C20) and more modern manufacturers use Neutrek PowerCon connectors due to their ability to handle 20Amps continuously.
Very unusual indeed.

[nevetslab]

I expect one side of the common mode choke has failed. These are only rated at 6Amps (C14) so many high peak current draw at switch on has proved too much for the poor filter.
Crown use a larger connector (C20) and more modern manufacturers use Neutrek PowerCon connectors due to their ability to handle 20Amps continuously.
Very unusual indeed.

These are only rated for 6A, eh? Interesting it's stated to be rated for 15A on the spec sheet I attached. The schematic didn't indicate a choke in series with the AC line internally, though that would be the logical place of failure. It would have to be extremely small, as this module is not much larger than the plain plastic IEC Male Panel Mount connector that I have installed temporarily to verify the amp itself is working (which it is). First time I've ever had one of these fail.

[Jon Snell]

These are only rated for 6A, eh? Interesting it's stated to be rated for 15A on the spec sheet I attached. The schematic didn't indicate a choke in series with the AC line internally, though that would be the logical place of failure. It would have to be extremely small, as this module is not much larger than the plain plastic IEC Male Panel Mount connector that I have installed temporarily to verify the amp itself is working (which it is). First time I've ever had one of these fail.

I think you were unlucky.
This is a Power Line Filter and the data for it is within your pdf, after all.
An exact relacement will probably outlast the life of the amplifier.