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Scope bandwidth limitation - amp or crt?

cs snipped-for-privacy@hotmail.com wrote in news: snipped-for-privacy@z34g2000cwc.googlegroups.com:

Actually,most TEK-made CRTs had a ceramic cast bell,gllued-on faceplate(nice and FLAT),and just the neck tube was blown glass. Only the early CRTs were all-glass.

I don't know.I have not seen any references to high-BW analog scopes for sale.

It's FAR cheaper to use a LCD video display and digitizing circuitry than to make a high bandwidth CRT for an analog scope;that's one problem.

Beware of used TEK TDS scopes,as they may be past the LTPS(long term product support) period,and thus have NO parts or assemblies available,and no schematics for troubleshooting.

--
Jim Yanik
jyanik
at
kua.net
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Jim Yanik
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Hello Jim,

OTOH there are still a lot of used one to be had a reasonable cost. Here in the lab the trusty old 7704A is dutifully continuing its job.

However, there are things you can't properly diagnose with an LCD screen. Also, I found that even on EMI analyzers (!) there are LCDs that produce an incredible racket above 30MHz. It's pathetic but once at a client I had to place aluminum foil over the display, hit "store" and then remove the foil to look at the spectrum. The only other option would have been to find a larger space for 10m measurements and look at the screen with binoculars (seriously, I have done that). This was never the case with the older HP gear.

Regards, Joerg

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Joerg

Joerg wrote in news:REmPf.57075$ snipped-for-privacy@newssvr21.news.prodigy.com:

Yes,I was saddened to see the 7000 series disappear. (except for the 7500 models!) They were potent,flexible scope platforms. I too would much rather use an analog scope than a digital scope.

--
Jim Yanik
jyanik
at
kua.net
Reply to
Jim Yanik

Hello Jim,

I even bought a cheap digital camera for the lab, to be able to document the screen contents since there is no GPIB except for the really slow

7D20 digital module. Well, at least that beats the messy fumbling with that instant film back in the 80's.

Regards, Joerg

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Joerg

I wonder if that might actually make a hobbyist attempt at a custom CRT more reasonable?

I would certainly be nice to be able to get in there and change things, rather than have each attempt be a one-shot try.

Idle contemplation though... no space for such a project even if there were time and funds.

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cs_posting

cs snipped-for-privacy@hotmail.com wrote in news: snipped-for-privacy@u72g2000cwu.googlegroups.com:

The flat glass,glued-on faceplate also gave us the internal graticule. Earlier CRTs had external faceplates,or bonded-on faceplates that sometimes debonded or got bubbles underneath.

I dunno;it wasn't an easy task even for TEK,they had to trash batches of CRTs,some lines had very high reject rates.The 2465 CRT was quite an engineering feat with it's quadrupole lens that eliminated the mesh lens and enabled a shorter CRT and still retain high BW capability,also achieving low deflection sensitivity.

Uh,even TEK did not repair or alter ceramic-belled CRTs after they were finished,evacuated and tested. They did break them up,and reuse the electron gun/deflection structures,and recycled the faceplate glass. (or they used "seconds" for internal TEK use;that's how I got a FREE new CRT for my 2213!) We had to return old CRTs to Beaverton for recycling.

--
Jim Yanik
jyanik
at
kua.net
Reply to
Jim Yanik

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