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Sherlock Ohms

Bad Parts Plague Oscilloscope

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Rob Spiegel
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Re: Quite a maddening problem
Rob Spiegel   5/1/2013 4:37:22 PM
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That's right, Chuck. But until you actually experience this problem, it would be quite natural to discard the solution if the replacement part did not correct the problem.

Eric Tucker
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Iron
Tek Models
Eric Tucker   5/2/2013 9:07:27 AM
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Chiming in not as an expert but as an enthusiast of the classic 500-series Tek 'scopes: The Type 547 isn't a storage 'scope, perhaps the author meant the Type 564? I've owned both and still have the 564, which still stores a trace! Not bad for a 50-year-old instrument.

Rob Spiegel
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Re: Quite a maddening problem
Rob Spiegel   5/2/2013 12:58:40 PM
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Good point, Eric. So you would argue that Sherlockm shouldn't have been needed on this case. The problem should have been solved by quality control before the engineer began work on the project.

Rob Spiegel
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Re: Quite a maddening problem
Rob Spiegel   5/2/2013 1:03:56 PM
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BrainiacV -- from these comments, I get the feeling that this problem is not uncommon at all. I guess troubleshooting  should come without any assumptions, including the assumption that the parts -- even new ones -- are not faulty.

armorris
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Platinum
Re: Root Cause
armorris   5/3/2013 3:59:20 PM
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It might be heat from the soldering iron. I remember those ceramic terminal strips, and several components might be soldered into those silver-plated notches. It might require a lot of heat to overcome that much thermal mass to melt the solder and replace the diode.

William K.
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Bad parts right from new stock
William K.   5/4/2013 1:02:41 PM
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Some of the mor4e frustrating repair projects come from assuming that a new part is good because it is new. Out of tolerance capacitors and wrong marked resistors can lead to an extended diagnostic chase, that is certain. Mismarked transistors also, particularly when a PNP is found marked as an NPN. So for some things that need to be correct the first time they are switched on, validating the "ggodness" of every part winds up being a real time saver. 

Critic
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Platinum
ESD!
Critic   5/6/2013 4:10:21 PM
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ESD!

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