Tektronix MSO56 - Does not detect probes anymore / TekVPI probe interface

[steffenmauch]

Hello together,

I do have a MSO56 from 2019 which does not detect any probe which is using the TekVPI® probe interface automatically.
E.g. the current probe is powered, the red LED is blinking but nothing else; a TPP0500 probe is not detected as well.
This is true for all six channels.

When running the diagnostics, it is reporting 'Probe Interface Board(Source) and Front Panel (Destination)' failed.
Does anyone have further information hereon?

The service manual is available but my initial guess that the ribbon cable is loose seems not to be true.
https://download.tek.com/manual/5-Series-MSO-MSO54-MSO56-MSO58-Service-Manual_EN-US_077130700.pdf

A visual inspection of the Probe Interface Board has not shown any sign of damage; so I am a bit lost at the moment.

Any ideas how to track the error down or does anyone know if this is a common error for MSO5x?

Thank you
Steffen

[PartialDischarge]

If you eventually take it to the Tek repair service, let us know how much will it be, I'm guessing in between 100% and 300% of the new scope price.

[steffenmauch]

Well, service quote was approx. 10K ...

I did some reverse engineering:

U201 is a 'MKE02Z64' ARM Cortex-M0 microcontroller
all regular TekVPI signals are routed to this MCU and protected with DA112S diode arrays e.g. U901, U801 etc.
J201 is a 2x5 programming adapter without JTAG but with SWD

U501, U401, and U301 is a 'CY7C655-32' USB Interface IC USB-Serial Dual CH Bridge
the D+/D- is routed to the additional two pins above the regular TekVPI interface
Compared to
https://w140.com/tekwiki/wiki/TekVPI_connector
it does have two additional pins which are used for D+/D- of USB.

Each TekVPI interace has a load switch on its +12V rail (U609, U608, U607, U606, U605, U604, U603 and U602) 'LDRB' in a SOT23-5

The RGB led of the power button as well as the power button are routed individually to J1501.
This confirms, that my initial guess was wrong as the ribbon cable is required for switching on the oscilloscope.

There are two buffers U1501 - LC125A marking and U1502 - AHCT125 marking.
https://www.ti.com/lit/ds/symlink/sn74lvc125a.pdf
https://www.ti.com/product/de-de/SN74AHCT125

The signals of the MCU are routed to this and the input/output then to J1501.
There are three inputs and two outputs from the MCU shifted to J1501.
The output enable signals are all tied to GND.
Pin 7 and 8 of the J1501 is USB

As the original failure is mentioning SPI, I guess that
MISO and IRQ are the outputs
MOSI, CLK and CS are the inputs

I will try to connect a logic probe to the signals and record if there is some traffic as I do not believe that U1501 or U1502 is the issue but instead MCU U201.
I will also try connecting a debugger to U201 but even if it is running, I guess that Tektronix will have locked it.
If it won't run, I would need the binary of the MCU ...

Honestly, I think that this will be the point where the repair will stop as nobody will have that image or?
Or does someone have a spare Probe Interface Board or is willing to try to read out the MCU?

[PartialDischarge]

Well, service quote was approx. 10K ...

That is fkin amazing. One buys Tek and pays more expecting reliability, and if it fails you're screwed. They should make public the repair fees

[voltsandjolts]

For 10K you could buy a new scope, copy bits you need and resell!
But I think any MCU code would likely be readout protected.

https://www.sjelectronics.co.uk/tektronix-mso56-5-bw-350-350mhz-bandwidth-5-series-mixed-signal-oscilloscope.html

Best of luck to you.