Re: 7834 Missing Trace


Colin Herbert
 

To remove a plug-in with a broken pull-tab:

If you can grasp some of the pull-tab with long-nosed pliers, do so once you have put something to act as a pull-handle onto one of the BNCs (it doesn't matter which, but don't obscure the pull-tab too much and don't use a BNC Tee-piece; they simply pull apart. Something like a Normalizer is perfect). Pull the plug-in forward gently without pulling the whole scope off the bench and then give the pull-tab a pull with the long-nosed pliers while keeping pulling gently at the plug-in. You might hear a click as the retainer disengages and the plug-in start to move out. Once you have got the plug-in out of the scope, don't put it back into that or any other scope until you have sourced a spare pull-tab or disabled the retaining ability of the broken one, otherwise you are back at square one.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of sdferg7@...
Sent: 08 August 2020 17:08
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7834 Missing Trace

The trace only gets fuzzy when I have the calibrator signal plugged in, and only the top half. The issue still comes and goes, usually after I change a setting, e.g. the vertical channel. With no signal the only time the trace flickers from moving up and down is when it goes through the trigger.

Unfortunately the scope only came with 1 vertical plugin, in the right slot, and the pull tab is missing. Is there an easy way to get it out without much disassembly? In the manual it seems the only way to get the black follower tracks out is to have their respective plugin removed to access the screws. When I select the empty left vertical plugin slot I get a flat trace slightly tilted clockwise, maybe 1 or 2 degrees.

I also discovered I was mistaken about the 2 dots, they actually appear to be the minimum and maximum of the right horizontal plugin from the calibrator signal I had plugged in. If I select chop with no signal I get 1 brighter dot from the right plugin, still nothing from the left.

I also did more testing on the scope's calibration. Last night after the scope was pretty warm I tried measuring a 1.6V battery at 1V/div which showed on the scope as about 3/4 of a division. This morning I tried the same with the scope cold and it came to almost exactly 1 division. This seems to follow my previous experience with the scope reading lower as it gets warm. The scope also seems to read slightly off on the frequency of the calibrator signal, each period shows as slightly less than 1ms. Of course that could be an issue with the calibrator.

Shane

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