Siglent SDG800 powers on but doesn't respond to key presses

[ESTechnical]

Hi everyone,

I have picked up a siglent sdg800 that doesn't respond to any key presses. When the unit is switched on, the display works and all the front panel LEDs light. It gets past the splash screen to show the settings of a sine wave output, but nothing more happens. I have got the unit apart and probed around a bit to find there is no activity at all in the front panel ICs related to the buttons and LEDs. There's multiplexers and shift registers on the front panel PCB but no serial data or clock pulses to be found anywhere. I checked for the correct supply voltages everywhere there's a labelled test point. I can't find a schematic or service manual online.

I've checked the front panel FFC is connected properly and continuity tested a few pins that I can follow from the shift registers and they are connected all the way back to the main board and then disappear inside the PCB layer stack and presumably go all the way to the microprocessor.

Do you think I should cut my losses and dispose of the unit, or is there something that could be done to fix it? I had a look around the other siglent threads but didn't find anything about the controls not working. I hope I haven't missed anything obvious!

Thanks very much
Ed

[bdunham7]

If you can identify the ICs that seem to be inert and then find a datasheet to show you the power and ground pins, you can test directly there to verify that they are powered up. 

I don't know if there is a front panel lock utility, but you might look into that.  I wouldn't think that it would remain on through a power cycle, although there could be  a malfunction related to it.

[ESTechnical]

I've been testing the serial in and clk pins of the shift registers - it looks like these drive rows or cols of the keypad matrix and LEDs on the front panel. Nothing is coming to them from the main board. I suspect the ICs on the front panel are fine, just they receive no data and sit in a default state. There's no shorted pins, they are not heating up etc. They definitely receive the 3.3v supply.

I can't trace where the signals come from/go to on the main board anywhere beyond the FFC connector. It looks likely that these are going straight the main processor which is a BGA package.

[ESTechnical]

I contacted Siglent and they sent me firmware recovery/update files. The unit now works! I am really impressed with support from Siglent!