More switchmode power supply grief - Cisco IGS router

[Maciej W. Rozycki]

On Thu, 3 Feb 2022, Peter Coghlan via cctalk wrote:

> Today I finally managed to check it out.  The ceramic F4A mains input fuse
> beside the power switch on the back panel had blown.  When I opened it up,
> I found a POWER-ONE MAP80-4000 power supply.  The main chopper transistor
> labelled Q1 on the PCB is almost a dead short.  It is a large plastic
> packaged FET mounted on a piece of aluminium which is in turn screwed to
> the case for heatsinking.  Unfortunately, there are no markings on it so
> I have no idea what to replace it with :-(
> 
> As Q1 is shorted across all three terminals, whatever drives it may be
> damaged too :-(
> 
> After finding screw heads hidden under the label, I managed to extract
> the PCB from the case and found some corrosion underneath, possibly from
> leaking electrolytic capacitors :-(

 This PSU seems to have been used across various Cisco devices and I had 
one fail several years ago in a WS-C1202 Ethernet/FDDI switch, also having 
suffered from leaking caps.  Back then RS still had it in stock at a hefty 
price of £489.60: <https://uk.rs-online.com/web/p/products/8338173/>, so I 
chose to recap the failed one and thanfully it has continued working ever 
since.  You may try to enquire with the manufacturer.

 Good luck with bringing yours back to life!

 FWIW,

  Maciej