Tek 2440 repair help needed

[cncjerry]

I picked up a 2440 cheap with plans to give it to my brother.  It starts up, runs diagnostics and they all seem to pass.  Then it said to run self cal and ext cal.  Self cal runs.  When I hit ext cal, it fails without any other errors.

I'm going to look for the manual but in the meantime, can someone give me a hint as to what is going on?

Thanks

jerry

[cncjerry]

well, I'm progressing.  I'm able to exit out of the diagnostics by punching the menu off/extended functions.  I hooked onto the calibration signal and hit the auto button and all looks well.  Signal should  be .4V into 1Meg and it is.  As I dial down the horizontal though, it seems to be looping even though the display reads the correct setting.  So after 500us,  200us  should have fewer waveforms and it has more like it went higher in time opposed to lower.  So the display continues like this until I get into the nanoseconds and then it starts to look ok except at 200ns, the square wave looks like a triangle or something. 

Anyway, this all looks like a calibration issue.  I'll start with a new battery and try to get into the EXT calibration.  Unless someone thinks this timebase is indicative of some larger problem?

Jerry

[cncjerry]

not trying to look like an idiot, but the issue with the time base is that the calibrator varies with timebase so that was the issue.  The calibrator does look funky at 5Mhz though. 

So anyway, for $50 it looks like an interesting scope.  Nothing like my others but will be fine for my brother once I swap out the NVRAMs and battery.

Jerry

[ChuckDarwin]

If the calibration/config nvram isn't dead yet--assuming you are replacing it--you might want to read it out and copy it to the new nvram to save the extended recalibration step.

[cncjerry]

It must be dead because it is asking for external calibration which I'm not afraid of having all that is needed.

I can't figure out the lack of battery.  There must have been a later change in the schematic as my unit no longer has a battery just a jumper across where the batteries should be.

Thanks

Jerry