[ARC5] Scope Question

[Bob kb8tq]

Hi

Interestingly, if you head “over the ocean” there are guys working on street corners who will happily 
pull a BGA off a board, re-ball it and put it back down on a board. Our surplus market no longer 
has cool stuff like BGA rework gear for pennies on the dollar. Their surplus market is flooded with
that sort of stuff. 

Bob

> On Mar 21, 2018, at 10:31 AM, J Mcvey via ARC5 <arc5 at mailman.qth.net> wrote:
> 
> It's so true about the "new stuff" having less chance of being repaired due to "unobtnaium" parts.
> The problem is not limited to scopes either. Radios, Tvs , surround sounds, you name it and it has custom ICs that are not or soon will not be available.
> Some of the BGA components fail not because of the silicon, but because the solder connections crack. Reflowing them will sometimes restore operation, but is not always reliable. They actually need to be removed, cleaned and re-balled- but who wants to do that?
> 
> Modern LED TVs have a high panel fail rates because they overdrive the LEDs which guarantees their early demise 
> The mfrs do not make the LED strips available , besides it's a bear to disassemble an LED panel anyway, so the 3 year old TV goes on the curb. .
> 
> Sadly much of this present day "high tech" is not going to survive the test of time like the old discreet technology has.
> Not only is it planned obsolescence , but with a built-in self destruct mechanism too!  
> On Tuesday, March 20, 2018, 6:19:11 PM EDT, Jim Wiley <jwiley at gci.net <mailto:jwiley at gci.net>> wrote:
> 
> 
> Wayne - 
> 
> 
> 
> The switch setting "ground"  means "disconnect the incoming signal going into the scope and ground the scope signal path, so the input INSIDE THE SCOPE is connected to ground". 
> 
> Or to put it another way,  internally inside the scope the "ground" setting opens the circuit connecting the signal from the external probe  (or input cable) and the oscilloscope internal amplifier so there is no connection  from the outside world, and instead shorts the vertical amplifier input to ground.  
> 
> The other two settings are used to set the vertical amplifier as a DC coupled or AC coupled amplifier, to display signals.   The "ground" setting is used so the operator can make sure there is no external signal coming in, and can thus get the trace "on screen" somewhere so he or she can see it (giving a place to start).  
> 
> I hope this makes sense.  
> 
> 
> 
> - Jim, KL7CC
> 
> 
> 
> 
> 
> 
> On 3/20/2018 7:32 AM, Robert Eleazer wrote:
> 
> I am troubleshooting a Tektronix 2236 scope.  Tektronix says to use another scope to do that.  Now, the general settings they say to use for the test scope says for the coupling switch, which offers the options of AC, Ground, and DC, is to use "Ground."  I set the coupling to Ground and I don't get any reading.
>  
> Does this make sense to y'all?  I get readings with either DC or AC coupling selected.  The signals being measured are all pulsating DC voltages of various kinds, such as square waves, triangle waves, etc..
>  
> Thanks,
>  
> Wayne
> WB5WSV       
> 
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