Electronics > Repair

Tektronix MDO4104-6 Front Panel Microcontroller Failure

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My front panel PCB on my MDO4104-6 scope was not responding to push button presses nor knob turns. My oscilloscope automatically was powering up when AC power was applied. The oscilloscope does boot up and channel 1 does appear. However, I can't adjust settings due to the front panel not working. Some of the front panel LEDs were on at random boot times. I can connect to the oscilloscope through OpenChoice with no issues. I've tried updating the firmware to the 3.18 version (last version to be made) but the front panel was still not functioning. I then ordered a replacement microcontroller for the front panel PCB and soldered on a new part. Now the oscilloscope won't power on (as expected since it controls the remote signal to the power supply). I forced the power supply to turn on when AC is applied by shorting the remote jumper header on the power supply. The oscilloscope boots up but no LEDs are on and no buttons work on the front panel. This is to be expected since the microcontroller is blank with no program to run. I would like to know if there is a way to reprogram the microcontroller on the front panel PCB. I don't see any information on firmware other than the 3.18 version that I don't think updates the software on the front panel PCB, but I could be wrong. Also, when I try the USB stick with 3.18 firmware, my oscilloscope won't try to update because it detects that the oscilloscope already has this firmware. I did place a TXT file named "forceinstall.txt" and this does force an install of the firmware, but the front panel still is dead. I did check with an ohm meter my soldering of the microcontroller to the PCB and from pad to pad to confirm no solder bridges. I ended up trying the LOCK command using the OpenChoice software tool to see if the main processor is preventing a firmware update to the microcontroller. I ran the command and forced the install with no luck.

Does anyone know of how to program the front panel PCB directly? I'm assuming that the firmware for the front panel is not public knowledge. When I reached out to Tektronix directly they stated that it would cost me +$5K and it may not work after they try fixing it.


Will Tek sell the board?

Hello joebot5,

The front panel microcontroller U302(I think) is a programmed part.  Without the flashed program it will do nothing.  When the scope FW is updated it checks for the latest code in the front panel controller and will update if needed.  If the boot sequence does not see the program in U302 the scope will not boot.

 As to a fix, find another MDO4k pull the chip and save a copy of it with prom burner.  Then burn that program into your new chip. 

Sorry it isn't easier....

Hi Jwalling - Tek replied with saying they can try repairing the scope but the cost would be ~$5k and it may not work. They didn't offer selling me the front panel PCB. Thanks for the suggestion!

Hi mikehank - thanks for your response. That is a good idea - i just need to get a working MDO4K at least a working front panel. If anyone knows of one available out on the web that would be appreciated.


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