I bought this Microset PTS150 13.5v Power Supply Unit from Italy in October 2013* to keep my AGM batteries under continuous trickle charge and to power my 12-220v inverter directly at night.
*Nearly eight years ago!
July 9, 2021
Last night it suffered partial failure. The output voltage became unstable and it couldn't supply enough power to keep the inverter running, so my office computers powered down.
Into the workshop it went for investigation. The on/off switch had to be removed to allow the Printed Circuit Board assembly to be lifted out.
What I discovered surprised me. I was anticipating electrolytic capacitor failure. Instead, I found a failed (blue) PTPE capacitor.
In fact three of the five blue capacitors had failed in the same way. They had expanded and cracked the encapsulating plastic housing.
I replaced all five with (yellow) 100nF/100v capacitors, which I had in stock.
After reassembly, the output voltage under load was back to normal and stable.
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