[thingstodo]

This is one of the surplus DC/AC inverters that I have.

The idea is to use the isolated DC/DC section, where 12V is boosted to around 150 VDC, before it is converted to modified sine wave.

I got this surplus. The manufacture date is 2004, so it's not exactly leading-edge technology.

I did manage to get the screws out. The heat sink splits into an upper half and a lower half. There is a 'power board' on each half and an 'electronics' board that sits between, on a lip between the halves of the heat sink.

There are several signal cables going from the electronics board to various locations. The power to the electronics appears to be unfiltered input voltage (10 - 15 VDC) which goes through a small regulator. The electronics board has a dark flash-burn on the bottom and a couple of resistors that have corroded badly.

The majority of the control signals appear to be switching signals to 32 power transistors that switch the 12VDC through 16 step-up transformers. There is a pair of 35V capacitors and a pair of transistors for each step-up transformer. I was expecting diodes to rectify the AC pulses from the transformers, but I don't see any. There are 8 larger 200V capacitors which appear to be for the output stage, along with 4 inductors. There are a couple of smaller capacitors between the large capacitors. One of these has corroded off.

Each step-up transformer has a 40A automotive fuse. All of these appear to be fine.

I pulled all of the fuses and put regulated 12.8VDC at 0.9A max into the power feed. The power draw is about 0.3 amps.

Turn off the power and put a pair of fuses back in - far right top. Apply power - the same 0.3 amps draw. No output power. No power indication on the display. No noise.

Check a few terminals within the circuit. There does not appear to be signal switching on the electronics board. I don't expect that any of the switching transistors are stepping the 12V up to 150 VDC, or 75 VDC, or whatever the design is.

Turn off the power and put a different pair of fuses back in a different location - far left, bottom board. Apply power - same 0.3 amps draw. Check power on the electronics board. 12V in. 5V regulator is working. No signal switching. Check the intermediate outputs on the bottom power board. Nothing.

Re-assemble, put the cables back together approximately as it was when I started. This is a source of parts for further experiments. If I can figure out how the display works, that might be useful. Put the 40A fuses back in - again, convenient storage. Label as 'parts' and as 'badly corroded'

I have other units to test. I guess it's time to move on to the next one. Not a lot of useful information from this one.