While it was idling during my vacation the UPS had a burnout: a pair of 1N5404 power diodes (they split open and scorched the board), an IRFZ44V power MOSFET (shorted gate to drain), and a circuit trace (melted through). The transformer appears perfect, and the battery remains good.
I replaced components and fixed those faults; the unit turns on and the buzzer sounds momentarily like normal but there's no voltage on the regulated outlets.
If I had a circuit diagram (with voltages marked) I might be able to fix it. Are they available?
Or is there somewhere to send the circuit board for refurb?
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Get APC Powerchute Personal Edition for free and run it. If it says your battery isnt charged, check its voltage disconnected. Charge it with a car battery charger and see if its still a good battery. If not , replace it. If the battery is good, then check the charging voltage. Should be about 14 volts. if not, check the small transformer on the main board. Should be 120 in and 17 to 18 out. 4 diodes in a bridge for charge. The input to the transf has small fuse into it alone.
You could have done a very slow damage to the Yamaha if your UPS was not a pure sine wave type ( on line UPS ). Most of the UPS we get are called Off line type and are far cheaper than the On line pure sine wave type. The out put of the Off line type UPS is not a sine wave ( the natural waveform of AC voltage ) and strains the Power supply circuit of any device connected to it. Now if the humming sound is the same irrespective of the volume position, it is a power supply problem. You might be having a leaky rectifier diode or capacitor. First change the diodes and see if its ok then change the main filter capacitors too.
hello, ik got a lot of these UPS for repair. I exclude any battery problem that I suppose you already checked. The Systems I have here does all have problem at charger electronics (VT 9 or components around) mostly burned out (short circuit). No repair is possible as copper lines are burned.
Normally if this UPS is in working condition and the batteries are also good, you should be able to start the UPS by just using the battery cabinet. As soon as power is applied the fan must run and the 4 yellow led for battery/load should lit up. If it is completely dead, then a qualified technician will have to check the internal circuit. It has one main board on which all power components are mounted and a separate control board. Generally there is a 80/100 A than goes opened. I hope you can give us more information if the UPS is completely dead or the led comes up
Shutdown the equipment connected to the UPS, disconnect the load and remove the main power to the UPS. Open the UPS to see if you can see any sign of burning component. Confrim that the UPS is not Overloaded before the shutdown. If you are not an experienced techinician with UPS please contact an experience Technician because there are life Voltages in the UPS which can cause electric shocks.
firstly check your sleeping timer set ups. if that is okey, then check the following
the power supply components eg
power transistor on the power supply lekage
zener diodes, power diodes of the bridge rectifier.
in short the supply is drowing to much current, hence semiconductors are heating up and reach a cutoff point, and saturates