Bad zener Powerware 5125-1500

I was able to replace parts on the circuit board (P/N: 128301_timer_pcb) to fix this issue on my KCO253CU Kitchenaid Toaster Oven. R1 was visibly burned. On further troubleshooting, ZD2 was found to be shorted.
Known Failed Parts Replaced:
R1: 47 Ohm 2 Watt resistor
ZD2: 47V Zener Diode
Other Parts Replaced
C1: 1.5 uF 400 Volt Film Capacitor
ZD1: 5.1 V Zener Diode, tested OK but replaced anyway.
See attached photo of circuit board for component part numbers.
John W.

If this is the 1N5369 51volt zener, then it is a 5 watt part, and apparently is intended to dump a fair amount of heat, hence the wattage rating. About the only thing I can suggest is to go to a higher wattage 51 volt zener, but if the units are working, no action whatsoever may be warranted. Failure of this zener seems to cause a failure to charge the battery, but the good news is that (at least in the two I have worked on) changing the part (about $0.50) gets it working again with no additional damage.

For what it's worth, in the older variant of the Prestige inverter card, this diode is not present - the charger has an IRF540 MosFET, which also seems to be prone to failure, but once again, simply changing this part has never failed to fix a unit for me, and cost is $1.59 . . . far too cheap to not give it a try.

The LEDs are actually indicating the amount of load on the UPS and only indicate battery charge level when running on battery power. You can email [email protected] if you'd like to follow up.

M-PW9120 6000i protection diode is damage when we connect the ups with main source otherwise backup is ok only protetion diode is damage

chek the optocoupler 3sd12

Try the legacy products page on eaton.com/powerquality (go to products and services and then click on the legacy products link) or call 800-356-5794. http://powerquality.eaton.com/Products-services/legacy/prestige-info.asp

The zener diodes are 1N4774, I believe they are one watt. Try 3 watt metal oxide for the resistors. You might as well replace the 6800uF 63 volt main filter capacitors and the 220uF 50 volt capacitors while you're at it. Half the time the heat that cooked your other parts takes them out as well.

I had a DC bus fault error displayed.

So I unplugged battery, then turned on UPS. It said Batt disconnected of course.

So when I plugged in the batt while the UPS was on, and held the power button for a few sec, the UPS displayed Batt testing.

After a few moments it was back online and had no faults!

Worth a shot.

did you get what you needed?

your problem could be related to a dispay board or possible CSB board.