More switchmode power supply grief - Cisco IGS router
Peter Coghlan
cctalk at beyondthepale.ie
Sat Feb 5 05:27:54 CST 2022
"Maciej W. Rozycki" wrote:
> 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!
>
Thanks Maciej. I'll be surprised if the manufacturer has records of
what they used for the chopper in power supplies 30 years ago - who
knows if their design has changed between then and now. I'll be even
more suprised if they will talk to me about it but I guess it's worth
a try.
Regards,
Peter.
>
> FWIW,
>
> Maciej
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