Well.....I'm putting my 465B final entry here because it started here.
![Grin ;D](https://www.eevblog.com/forum/Smileys/default/xgrin.gif.pagespeed.ic.QVVz6XIT20.png)
Final calibration and wrap up of this 465B/DM44 project. My approach to checking a scopes calibration is rather simple. Check the major functions that are most important but don't get tied up in minor stuff that for a hobbyist like me doesn't really make much difference. Besides, I'm not a cal lab nor do I have the equipment to do a traceable calibration. So I break it down to the following categories:
CRT/HV: Check the bias (which for some reason was way high), check the HV. Is the trace clean and sharp? Is the focus OK? Yes and yes. Done.
Horizontal/Sweep: Is the trace linear? Is the sweep time accurate? Yes and the sweep time is dead on. No adjustments required. Done.
Trigger: Do the trigger circuits work? Easy to trigger? Is it stable? Yes, yes, and yes. Done. I also did a quick check of the delayed sweep and all seems good.
Vertical: Is the vertical gain accurate? DC balance adjusted properly? Here's where it needed some minor tweaks. Both channel 1 and 2 needed an equally small increase in gain. And the DC balance for the channel 2 invert circuit needed adjustment. Other than that the vertical circuits looked good.
Attenuator/Compensation: These input circuits are absolutely critical for faithful trace display and frequency response. My fear is that some twiddle happy “tech” got in there and screwed them up. Which is easy to do and a royal pain to fix. I can rest easy. No one has been in there since the scope left the factory. They are perfect. Here's 1MHz square from the Heath IG-4244 Scope Calibrator. It's excellent across all attenuator settings and both channels. No peaking or rounding. Makes me happy.
![](https://imagizer.imageshack.com/v2/xq90/922/tdLU2T.jpg)
And here is 10MHz. For a 100MHz response scope this is also excellent.
![](https://imagizer.imageshack.com/v2/xq90/923/5qv41S.jpg)
And finally, the DM44. The DCV and Ohms were calibrated a few weeks ago when this unit was on the ill fated 465. I did not calibrate nor check the Time functions as it's a don't care. And when I get a chance I'll see if I can fix the temperature probe. But other than that this 465B/DM44 is done.