Cheap oscilloscope sold as "powers on, blank screen" soon after the seller got back to me to say "it won't power on, must be a PS problem".
Once received opening the scope I found the line trigger connector disconnected from the PSU, standby PSU was working but main power would not respond to power soft key press.
On primary side there's a 2 pin connector that can be used to force the main power on, the connector is same type as the line trig. one, I imagine the seller had last minute regrets on selling a scope that may be a too easy fix, went in to check to do whatever he could and went and connected the line trig connector in the wrong place...
Found TL3842 (60
between Vcc/GND pins), 2SC1815 (power enable to the 3842) and 5.1
series resistor on Vcc open, fits well with the wrong connector scenario.
After replacing these main power and soft key work, so I get a scope that powers on with a blank screen.
Checking around with the thermal cam. doesn't show anything alarming, doesn't show there's much going on at all actually.
On CPU board 3.3V power is good.
The line trig. leads to a trigger selector daughter board on the lower PCB (F.E. and acquisition), expecting the miss-wiring may have caused havoc there I checked for burnt components and tried removing the full acquisition PCB in case it was holding the CPU bus low. No better...
Next suspicion was a corrupt firmware so I started looking for that and came across these:
https://wiki.leedshackspace.org.uk/wiki/Electronics/GDS-820SThe oscilloscope has required re-flashing several times. If after pressing the standby button the LCD lights up and displays a blue screen but does not boot after you waited for more than 20 seconds, then its likely the oscilloscope has experienced this issue again.
https://www.gwinstek.com/en-global/products/detail/GDS-800Firmware:
https://www.gwinstek.com/en-global/products/downloadSeriesDownNew/12124/1054I first tried Realterm on the serial port to see if it was responsive, Power On Reset does give an output from what looks like a bootloader.
Next the Instek update software, which does complete the update sequence but the scope is still in the same state after the update.
Probing at the HY29LV160BT flash during a POR shows bus activity for a few seconds then seems to freeze at one point, buses still active but probably stuck on a very short loop.
Probing HY29LV160BT during firmware update shows no bus activity at all, so although the CPU responds to the software to initiate the update it doesn't write the received data to the flash.
Broken bootloader or hardware fault?
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