Electronics > Repair
Tektronix TDS 820
dgimb:
--- Quote from: David Hess on August 21, 2024, 03:47:01 pm ---
--- Quote from: dgimb on August 21, 2024, 12:40:38 pm ---The falling edge signal of DIR signal was wrong.
The reason was not signal on the RD*\1 pin on U1178.
--- End quote ---
So with none of the buffers producing the correct output, something earlier in the logic was the problem.
I would not expect that kind of output from any TTL gate because open inputs usually pull high, but FAST TTL has a lower high level input current.
--- End quote ---
Pin RD*\1 did not receive a signal from another part of the circuit(see screenshot).
RD*\1 had about 2.3V and this was an undefined state for trigger.
It was resolved with a long wire through the main board :)
dgimb:
--- Quote from: TERRA Operative on August 21, 2024, 04:15:42 pm ---
--- Quote from: dgimb on August 20, 2024, 05:01:40 pm ---Thanks for the advice.
I'm going to backup the oscilloscope firmware and use the "NI GPIB-USB-HS" adapter to do it.
Can you give me some information about this process?
What are the important points here?
Thanks!
--- End quote ---
Here's the instructions and tektool DOS app attached (Can be run from command prompt in Win10).
Also info on unlocking options too.
I've also added some floppy disk tools that will allow you to copy in and out the NVRAM and Calibration data (To backup your cal data. I have seen the EEPROMs go bad once or twice).
Be very careful about what you copy in! Make absolutely sure you copy OUT first, maybe twice then generate checksums and compare to ensure you have a good read.
--- End quote ---
Thank you very much for your help!
lordium:
I recently just happened to buy one of these TDS820 for some testing. I did a backup of the firmware and nvram (v2.03e) and unlocked the FFT (option 2F). I attach here if anyone needs in the future.
Unlock option 2F (FFT):
unlock nvram switch on side first, send commands over gpib, then lock, reboot, done
PASSWORD PITBULL
WORDCONSTANT:ATPUT 327689,1
commands I used to get the firmware/nvram:
./tektool -r NVRAM_all.bin -b 0x04000000 -l 0x100000
./tektool -r firmware.bin -b 0x01000000 -l 0x400000
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