Re: Another scope 7854
On Fri, 5 May 2017 01:24:00 -0500 (CDT), you wrote:
yOn Fri, 5 May 2017, David @DWH [TekScopes] wrote:I have seen this before where the waveform edges were distorted by aThe 7000 series uses a separate internal trigger path which originatesI will try this. I did re-seat the two ICs.
lot of ringing. This might be produced if one of the active stages is
saturating or clipping.
I am curious why enabling DC Offset coupling seems to fix the issue (I amIn both cases, the operating point of the active stages changes. The
position control does the same thing; does it have any effect on the
I did see that the base of Q426 was about 4.6V DC, rather than the 3.2V onThere are two version of the 7A18. The schematics show that the older
design has +3.2 volts at the base of Q426 and the newer design has
+4.7 volts at the base of Q426.
The same signal is applied to the signal channel switch and the
trigger channel switch so if it was distorted at that point, then I
would expect it to show up on the screen.
With the traces centered, I would compare the DC voltages between the
two channel switches with different channels selected to see if one
obviously has the wrong operating point.
I would also apply a square wave to channel 2 and measure the waveform
at the output of the trigger channel switch and at the collectors of
Q480 and Q580 to see if it is distorted. The signal levels at those
points are high enough to allow this.
FWIW the voltage rails in the plugin are spot on.Those are Berg Miniserts. If you are interested and cannot find the
datasheet online, then I can make it available.