I recently fixed one customer scope whose attenuator
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was not making 50 ohms in the 50 ohm position. The problem
turned out to be the latching relay in the attenuator section
had a "patina" on its gold plated coil pins, that was preventing
the coil from having continuity.
A clean up with deOxit red straightened out the problem.
On Fri, Dec 27, 2019 at 07:25 Jose Alfredo <firstname.lastname@example.org> wrote:
Leo, thanks for helping me. I removed the 50 ohms terminal and things go
worse. See: https://youtu.be/JeFw-dr9V3M
You may have a bad or flaky input attenuator.
Set the scope to DC coupling, and measure the resistance from the inner
conductor of the input to the shell. It should be 1MOhm on the dot across
all vertical settings.
Set the coupling to AC, and you should measure infinite input resistance.
Set the coupling to 50Ohm and you should measure 50Ohm.
If any of those are off, the attenuator has problems.
The contacts on these attenuators can develop oxidation or other problems
that cause them to either not complete the connection, or to go high
resistance. It’s also possible that a previous user has burned out the
50Ohm termination resistor.