Re: 2465B DC Balance/Parametric measurement problem

Bob Koller <testtech@...>


You need to run CAL 2 and 3 first. The different Trig hybrid will need different cal constants, plus the bad one probably caused some too-far-afield constants to be generated. If the CAL's don't pass or correct the problem, then, maybe the Control board has a problem. Is the serial number of your instrument above B05xxx?

From: jmacwilliams
To: TekScopes@...
Sent: Monday, June 4, 2012 8:46 AM
Subject: [TekScopes] Re: 2465B DC Balance/Parametric measurement problem

With nothing connected to Ch1, Volts/Div at 5V, and input set to GND (it actually makes no difference what it's set to), I can set the reference line to 1 division from the top using the Position pot. Assume the bottom line is numbered 0, then there are 9 horizontal lines, numbered 0 to 8, 8 being the top line. Reference line is on line 7. Here's how it changes as I rotate Volts/Div thru its settings:

5v -- line 7
2v -- line 5.5
1v -- line 3.4
500mv -- line 7
200mv -- line 5.5
100mv -- line 3.4
50mv -- line 7
20mv -- line 5.5
10mv -- line 3.4
5mv -- just below the bottom of the display (line minus something)

So there is a pattern: 5v = 500mv = 50mv and so on. This repetition repeats for ch2 when the same deltas.

Hope that makes sense. I'm about to try changing the A5 board with a known good one.


--- In TekScopes@..., "Patrick Wong" wrote:
> Hi Jim,
> Back to your OP, how much does the trace move vertically, in major divisions?
> Patrick Wong AK6C
> --- In TekScopes@..., "jmacwilliams" wrote:
> >
> > Power on self test works with no problems reported. Switching Volts/Div for both Chn 1 and 2 causes the signal to move vertically on the display. I tried running the DC balance procedure and the scope executes the procedure, but the problem doesn't change.
> >
> > Parametric measurements do not work either. The scope tries to make a measurement, but ends up not finding the signal, and the Volts/Div ends up on the highest scale.
> >
> > The Trigger voltage reading is also incorrect. Connecting Chn 1 to the Cal signal, the scope will trigger on the signal when the Trigger voltage reading is somewhere -0.5 to -0.1 volts. The Cal signal is truly between 0.0 and 0.4 volts.
> >
> > I suspect all of these problems have a common cause. I've checked all the test voltages on J119 and all read correctly.
> >
> > Anyone have any ideas?
> >

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