Hi maybe someone can help me. I bought a broken 3000w inverter. I have managed to fix most of the problems. I now have a 230v output. Mppt works… It is a rebranded Apert inverter I believe.

The problem I have is when you switch the inverter off then it doesn’t stay on in standby mode. It keeps restarting every 2 seconds. So you can’t set any menu items that require standby mode. If you connect solar or mains then it stays on just not when only on battery it restarts.

I think it has something to do with the Sps power supply.

7 hours ago, Tony777 said:

The problem I have is when you switch the inverter off then it doesn’t stay on in standby mode. It keeps restarting every 2 seconds.

Just clarify when you switch off. If the rocker switch is off only PV charging can still work. When the battery is charged it should stay on if the rocker is off.

Do I miss something?

🤣 The problem is when you leave it off, sun is down and also remove the mains. Then it beeps then restarts and does this continuously. I would expect it to keep the lcd on for a while then go off. ( Like my Growatt inverters.)

The behaviour is the same as when you run it from mains and don’t have a battery connected.

On 2025/11/25 at 6:16 PM, Tony777 said:

It is a rebranded Apert inverter I believe.

I believe that it's a clone, which is not the same thing. They could have left off all sorts of things.

On 2025/11/26 at 5:48 AM, Tony777 said:

The problem is when you leave it off, sun is down and also remove the mains. Then it beeps then restarts and does this continuously.

The shutoff circuit is quite simple; it basically has to be U8 (per the schematic trace) or what drives it. Try shorting that opto collector to emitter; the power supply should shut off and stay off.

Restarting continuously sounds like bad capacitors in the power supply. You could try replacing the usual suspects.

Thanks for the help. I thought normal behaviour was that if you turned the switch off it would just turn the 220vac off. Then maybe go into standby after a while. What is the normal behaviour of the genuine units.

Edited December 12, 2025Dec 12 by Tony777

Just now, Tony777 said:

Some pictures

21 hours ago, Tony777 said:

I thought normal behaviour was that if you turned the switch off it would just turn the 220vac off. Then maybe go into standby after a while. What is the normal behaviour of the genuine units.

Right. But with the switch off and no charging sources (PV or AC-in), it should switch off after about 30 seconds. To be revived if PV is present next morning. I assume that your problem is that it doesn't stay off when the DSP commands the power supply to go off.

I've had a lot of problems with the opto isolators on the 145 V max Solar Charge Controllers. There is one opto dedicated to waking the inverter at dawn; if this is shorted or very leaky, it would restart immediately after shutting down, I think.

For example, U4 at the bottom of the below traced schematic (parts designators like U4 may differ, especially with 24 V models):

Hi this is what the inverter does when you switch it off. It cycles like this continuously.

On 2026/01/19 at 4:35 PM, Tony777 said:

It cycles like this continuously.

I'd say it has to be one of the transistors associated with the start circuit, or the associated resistors:

So Q10 or Q9 in the above.

Or possibly the SCC's opto coupler (if present) is shorted. Try removing the 2-pin cable from the Solar Charge Controller to the main board.

I managed to fix the problem. When I got the inverter Q24 was blown up so the inverter would not switch on. I had no schematic so I guessed and installed a 2N3904 when it should have been a 2N 3906. In my fiddling I managed to burn some resistors on the board.

https://powerforum.co.za/topic/888-circuit-diagram-help-needed-repairing-alfa-p-300024-off-grid-inverter/

My inverter is just like the one in the link.

Does anyone have the values of the resistors on the under side of the board specifically R 91 and R 102 or a high res picture of the underside. How hot does the step up transformer usually run at idle. Mine is running at 60 degrees Celsius only running a 6w led. Might be because I have not got the correct resistors installed.