E-ast 500W inverter teardown

I’ve bought the inverter for cheap in the outlet. As I assumed it’s not fully working, I decided to have a look first.

The case is a nice finned aluminium, acting as a big heatsink. There are 8 screws holding the case together and few more for the transistors. One part of the case goes off easily. The PCB slides into the bottom case nicely.

The unit. The unit. The unit. Cables. I received one pair of beefy cables with clamps, and two pairs of lighter cables (probably a bug, they are the same). These fell out when I opened the case.

The PCB inside looks nice and clean, it’s based on the standard KA7500 chip (there are two of them), there are two groups of four power transistors, each group on the opposite side of the case. Wires for the 12V input are pretty beefy (and inflexible). Only the fuse holders seem a bit fishy. I decided to investigate and found out they are in fact female Faston connectors soldered in a PCB! They are bent, and one of them is not soldered in place at all. It was an easy fix and everything else seems to be good to go.

A quick look inside. Notice the skewed fuses. One was not properly inserted into the board and not soldered at all! One transformer is also not inserted all the way, but it the connection seems to be fine. One group of power transistors, held nicely to the case. Tha KA7500 drives the inverter. SLF capacitor. Never heard of them. Beefy tracks reinforced with a lot of solder. Seems a bit dodgy, but is probably ok.

Using the unit

Official specs
Input voltage11-15V DC
Max input current49A
Output voltage230V AC +-5%, 50Hz
Max output current2.2A (*230V = 506W)
Standby input current≤0.5A (*12V = 8.4W)

After completing the unit back, it works just fine. The specs seem pretty nice, it is designed to work from car battery, and has undervoltage warning specified somewhere around 10-11V, and efficiency of 85%. The standby input current is not specified in the brochure, but the official website says 0.5A.

Let us see how these specs hold. I’ve tested with my Manson HCS-3200 power supply. Unfortunately, it only goes to 20A, which is just under half max load. I’ll get a battery for testing later.

After powerup, the device consumes 0.7A at 12V, that is 8.4W. My Manson was a bit confused by the inverter under load, and did not show current correctly, and I was unable to measure efficiency with any relavant precision. The undervoltage protection is realised by really loud and annoying buzzer, and triggers just under 10.5V. On the other hand, the fan is reasonably quiet and only starts under a load.

The inverter claims to output modified sine wave. Here is the actual output; I wonder why my Fluke 45 failed to measure the AC voltage.

The modified sine wave A close look at one period. A closer look at the waveform.

Although it does not resemble the sine wave, it is stable under load and works fine with my old soldering iron and my notebook adapter.