Measurement aborted HP 54503A

[xaaander]

Hello. I recently changed NVRAM.
When I want to use ''blue functions'', selecting  Frequency for example, I choise  canal 1 with bnc from AC rear signal, I got this message:
Function is off.
Measurement aborted.
It's the same with all function.
How to turn on function ?
Thanks you.

[Stray Electron]

I have a HP 54510A and a couple of newer 545** models and AFIK there is no way to turn off those functions.  I think that your message is due to some kind of malfunction and the software detecting that and is causing the measurement to abort.

[xaaander]

Ok. Thanks you. I 'll try to calibrage again

[Stray Electron]

  Have you checked that the rear output is actually putting out a signal? 

[xaaander]

AC rear signal is ok, but as you mean, DC signal isn't. Do you know what IC is using to create DC signal?
Small connector from BNC to board is ok.

[Stray Electron]

  No, I've never been inside of any of the HP 54xxx scopes so I have no idea. You might search through some of the old HP Journal articles and see if they have any articles about the 54xxx scopes. Those usually have a good technical description.  The only "repair manual" that I've even seen for the 54xxx scopes just say to replace the entire circuit board and there is no technical information.