Electronics > Repair
Tektronix TDS 540 repair
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feedback.loop:
Hi!
I am trying to repair Tektronix TDS 540 (with no A).
Mostly successful, but cannot figure out the last(?) problem:
Fully recapped and cleaned the boards in the process.
Desoldered DS1245Y-120 NVRAM, backed up in a programmer, soldered a socket, put the NVRAM into the socket.
Now it shows only one error: "FAIL ++ Processor", but seems to work fine. Passes SPC and other tests.
Seems to show all waveforms just fine. I don't see any problem with that.
After clearing the error log (using a GPIB command) and rebooting, two lines show up in the error log:
SEVERE INTERNAL ERROR diagnostic test failure pu_diag sequence
SEVERE INTERNAL ERROR diagnostic test failure extended cal librarian reset

I don't think this model has a calibration EEPROM on the acquisition board. Everything must be in the NVRAM. Is it possible that nothing is wrong with the hardware, and this is just a matter of clearing some error condition in the NVRAM?
Does anyone have a working dump of the NVRAM for this model? Firmware v1.10e
I would appreciate any help very much.
Tantratron:
I've never seen so far any no suffix or A or B serie for these TDSxxx, I just know C series and D series.

Since it is takes little time, maybe open your TDS cabinet then remove the Acquisition board to verify if there is or there is not the two small EEPROMs.

As for you NVRAM dump, did you save their content prior desoldering and did you have already that Fail ++Processor ?

feedback.loop:
I don't see any EEPROMs.
The error was there from the start together with a few more that went away after recapping and cleaning.
wn1fju:
If it is anything like the 2-channel TDS520 I recently repaired, the cal constants are stored on the "firmface" board, the board that sticks down vertically
between the front panel board and the processor board.

You should be able to find the NVRAM binary at   http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=01_ROM_Images_and_Drivers
Enter TDS540 in the search box at the top of the listing.

I guess I was lucky with mine - after the recap, everything worked fine with no errors and calibrated nicely.

You can also search around in the various Tek forums and will find a cute way to alter a couple of bytes in the NVRAM to enable the FFT processing.
wn1fju:
Here's the link to that forum entry on enabling the FFT:

https://forum.tek.com/viewtopic.php?t=136932

Worked fine on my TDS520, although the splash screen at startup says nothing about the options now being enabled.  Yet, all the FFT menus are now present and everything works.
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