[Test-Equipment] Advice about used scopes

[Mike Manes]

I've been told that the CRT is a popular failure in the 7000 series.
But it can be tested for remaining life simply by advancing the
brightness control slowly to max.  If the trace brightness tops out
and then gets dimmer, the CRT's on its last legs.

73 de Mike W5VSI

Chris Albertson wrote:
> Thanks a bunch for all the info.  Disagreements are good.  Let's us see
> both sides of a point of view.  As for my use of the scope.  I do want
> to be able to look at the waveform from  radio transmitters that works
> at frequencies of up to 50Mhz.   I need to be able to design and test
> RF transformers and RF mixers and filters at frequenies up to 50Mhz.  I
> want to see what is being sent to the antenna (or more likey dummy
> load)... A 20Mhz scope may not work for that
> 
> As for measurements.  My guess is that any used scope will not be
> calibrated well and the cost to calibrate it would be more than the
> scope is worth.   I'm working on getting (building actually) a
> frequency counter and a peak indicating RF voltmeter  I figure a used
> scope is for making relative measurements, comparing signals and
> looking at the shape of waveforms (is is clipping?)
> 
> My budget really is "$100 and up""  not "about $500".
> 
> Now, after reading some downloaded manuals,  I understand the
> serviceability of the older analog  4xx scopes.  I've skimmed over the
> service manuals and I think they are well written and I might be able
> to do some simple maintenance on those "portable" scopes.
> 
> Question:  What fails on the 7000 series scopes?  I had the idea that
> maybe I could get a 7904 and a good sock of spare plug-in modules.  If
> it's the modules like the vertical amp and the time bases that go out. 
> They sell for cheap.  I could buy two (or three) of everything.  But if
> it's the mainframe itself, well I guess they are cheap enough I could
> keep spares too but storage space is an issue.
> 
> One more question:  The 7904 has two vertical amp bays.  Do I
> understand this right?  With an amp in each bay I could have a dual
> trace scope.  Or with a dual channel amp in one bay I could have a dual
> trace scope.  What do I get by placing two dual channel amps in each
> bay a four channel scope?.  I've also seen scopes with two time base
> units.   I've not found this covered in a Tek manual , yet.
> 
> The 7000 is looking good _if_ my plan of stockpiling spares would  work
> but just getting a 465 seems simpler and will do what I need.  Maybe
> buy a "parts" 465 to keep in the closet.
> 
> 
> 
> 
> 
> Chris Albertson
>   Home:   310-376-1029  chrisalbertson90278 at yahoo.com
>   Office: 310-336-5189  Christopher.J.Albertson at aero.org
> 
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-- 
Mike Manes    manes at attglobal.net     Tel: 303-979-4899
"Things should be made as simple as possible, but not more so."  A. Einstein