Electronics > Repair

TDS744A: 1M input impedance measures: Ch3 = 160Kohm, Ch4 = 706KOhm [resolved]

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--- Quote from: John_ITIC on April 23, 2024, 07:15:21 pm --- I'm not sure how to actually use the 5mV/div, 2mV/div and 1mV/div setting because the scope will not allow me to select those fine vertical resolutions when I'm plugging passive probes in (min vertical resolution then becomes 10mV/div).

--- End quote ---

If you connect 10X probes w/ readout or select 10X manually for non-readout probes, the vertical scales are all multiplied by 10.  So with a 10X probe, the apparent 10mV/div setting is actually the 1mV/div setting to the scope.


--- Quote from: bdunham7 on April 23, 2024, 11:44:30 pm ---or select 10X manually for non-readout probes,
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AFAIK that cannot be done on the TDS7* scopes, probes without the readout pin are assumed to be 1x.

David Hess:

--- Quote from: John_ITIC on April 23, 2024, 07:15:21 pm ---This is an "organic acid, water soluble" flux and it is stated that hot water should be used for cleaning. There is no mention of flux remover or IPA. I'm not sure what the ideal cleaning procedure is.
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That would explain it.  I tested organic water soluble flux many years ago and rejected it because of the cleaning requirements outside of production.  I did not run across the leakage problem, but in retrospect that seems obvious.


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