More switchmode power supply grief - Cisco IGS router

[Jonathan Chapman]

With that much carnage, I'd probably drop a Mean-Well module in there. I believe there would be enough room for one or two in the IGS I have (taller white box, divider "shelf" over the mainboard, I don't know if there was a lower profile model).

Thanks,
Jonathan

------- Original Message -------

On Saturday, February 5th, 2022 at 09:17, Phil Blundell via cctalk <cctalk at classiccmp.org> wrote:

> On Thu, Feb 03, 2022 at 06:06:10PM +0000, 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 :-(
>
> Does that PSU have a PWM controller IC, or is it built entirely from discretes?
>
> If there is an IC driving the chopper transistor then you may be able to get
>
> some clues about the likely characteristics of the transistor from the IC
>
> datasheet. Is it definitely a FET? Some, particularly older, designs used
>
> bipolar transistors there.
>
> As you say there is a fairly high likelihood that other components on the
>
> primary side will have blown up as well so you might be looking at a fairly
>
> extensive repair. Are there any other obscure, unmarked devices or is this
>
> the only one?
>
> p.