On Nov 29, 4:56 pm, Jim Yanik wrote:
Fred Bartoli " " wrote :



Jim Yanik a écrit :
Doug McDonald wrote in
:

Sam Goldwasser wrote:

Reasons why I should maybe stay with my 485:

1) Better proprietary IC availability (?, don't beat me up; I
thought this was what I read...)
2) Easier to service/repair than the 2465
3) More robust for the beginner

Obviously if I am thinking like this, I have no idea what I
should ultimately do. What does everyone think? ducking
I'm an expert on these things.

Oh?

The 485 is the best portable
analog scope ever made. It is arguably the best analog scope ever
made, though the 7904 series competes well on the bench. Do anything
you can to keep one working. There is no substitute for a 485/7904,
and I've used them all, including $50,000 digital ones. For
repairing analog electronic oddities, digital frequently simply
doesn't work.

A 485 is 350 MHz scope.

The 2465 is a very poor substitute, though a good scope.

Doug McDonald

IMO,the 485 is much worse than a 2465,having lots of flaky attenuator
problems,a bitch of a power supply repair-wise,and less accuracy than
the 2465 series.And you get a better CRT display with the 2465.
The 2465 was the best portable scope TEK ever made.What killed it was
TEK selling off the ICO/Hybrid plant to Maxim,and Maxim cutting TEK's
throat by forcing a last-time buy on TEK-made ICs.
The 485s are getting really old,the HF switch contacts are degrading
and unavailable.
The 2465 is more serviceable -if you can get the parts.
the 485 has the same problem.

I worked for TEK for 21.5 years in their Field Service centers
repairing and calibrating these scopes.I'd much rather work on a 2465
than a 485. 485s were a PITA even when TEK was still issuing the mod
summaries on fiche.There were SO many ECO changes,you couldn't keep
up with them all.

I agree about the 7904 lab scopes being great.Had one on my bench.

Totally agree on the 2465.

As for the DSOs, the OP clearly don't know what good ones can do. See
the DSA/11k plugins series. That's simply the best scope I've seen.
Period.

I currently have a setup with a DSA and one 11A34 and one 11A33 diff
plug-in from which I *measure* signals at the 10uV level with
excellent accuracy (has been checked against some calibration
tooling). But the truely amazing parts are the plug-ins (11A33 & 11A34
checked) recovery from deep saturation.
Right now after a 200mV step down to 0V (on a 1mV/div scale), both
plug-ins show not more than 40uV thermal tail and recovers from
saturation in under 50ns. All this being very well behaved and hence
can
be well compensated for, pushing the performances one step further.

We're trying to find a 'modern' DSO doing that: nada, nothing.
The last we've tested (DPO7054 @ euro 15K) showed near 2mV thermal
tailing after a 200mV step.

What I wonder is what did make Tek losing the art of those exceptional
input stages...

Ignorant beancounters and overpaid upper management.
They thought they could sell off the ICO/hybrid division,and then buy the
same parts from the new owner,but Maxim decided TEK was not buying in
enough volume to make Maxim happy,and forced a last-time buy before
shutting down the production of TEK ICs/hybrids.


IIRC Maxim made them available to all comers, but no one else wanted
very many of them.

Tek could have had another vendor make them:they just did not want to
spend the money.

Unless and until someone decides to make third party parts to FULLY
support at least some Tek models (some replacement assemblies using
merchant parts would be needed) the best solution is leave old Teks to
Tek collectors and support someone who will commit to the analog
oscilloscope business.