Re: Measurements of ampllifiers

[[email protected]]

tubesforall wrote:
> Velleman (www.velleman.be) makes a very inexpensive dual scope and
signal
> generator controlled by a PC that will do the job. See PC-500.


I would stick to legitimate test equipment manufacturers, which
needn't be that expensive as many are available very cheaply at
hamfests today. The exception would be a serious oscilloscope-"simple
scopes" can be had for five to twenty dollars all day and repaired by
jackleg methods, but modern, calibrated, DC-coupled triggered sweep
scopes with attenuators and calibrated sweep are probably best bought
_new_. Or late model(still supported) refurb from legitimate test
houses (i.e. not *ucker.)

Fifteen years ago one was safe in saying "buy nothing but a Tek scope"
but Tek does not build actual oscilloscopes, per se, today. Iwatsu in
Japan is one of the last respoectable builders of scopes. Hameg in
Germany may still be at it as well, but I don't know.

People who "can't afford test equipment" are usually full of ****. And
if they really aren't they need to get a job, or a better one at any
rate. As the True Hams said in the old days,"If you have time to ham,
you have time to build". (There are very, very few true hams left.)

[tubesforall]

I would agree--you want real test equipment. I have a cal'd 466 dual trace
Tek scope (1980's vintage) that does everything I need except give digtal
sampling, FFT, and storage capability. You can get those for about
$150-$200 used. The Velleman complement costs about $800 for both
pieces--and is very respectable quality using a self calibrated front end
that is optically isolated. It is, however, a little fragile. Unlike the
Tek scope you can't hit the AC coupled front end with 1000VDC--it will zap
it for sure. If you can live with those restrictions, the combination of
rugged Tek, and cheaper DSO make a nice bench setup. The Velleman has good
software for running BODE plots with phase, and multiple stacked traces.
Again, it's not top end--but does the job for audio signals.


> wrote in message
oups.com...
>
> tubesforall wrote:
>> Velleman (www.velleman.be) makes a very inexpensive dual scope and
> signal
>> generator controlled by a PC that will do the job. See PC-500.
>
>
> I would stick to legitimate test equipment manufacturers, which
> needn't be that expensive as many are available very cheaply at
> hamfests today. The exception would be a serious oscilloscope-"simple
> scopes" can be had for five to twenty dollars all day and repaired by
> jackleg methods, but modern, calibrated, DC-coupled triggered sweep
> scopes with attenuators and calibrated sweep are probably best bought
> _new_. Or late model(still supported) refurb from legitimate test
> houses (i.e. not *ucker.)
>
> Fifteen years ago one was safe in saying "buy nothing but a Tek scope"
> but Tek does not build actual oscilloscopes, per se, today. Iwatsu in
> Japan is one of the last respoectable builders of scopes. Hameg in
> Germany may still be at it as well, but I don't know.
>
> People who "can't afford test equipment" are usually full of ****. And
> if they really aren't they need to get a job, or a better one at any
> rate. As the True Hams said in the old days,"If you have time to ham,
> you have time to build". (There are very, very few true hams left.)
>

[Robert Morein]

> wrote in message
oups.com...
>
> tubesforall wrote:
> > Velleman (www.velleman.be) makes a very inexpensive dual scope and
> signal
> > generator controlled by a PC that will do the job. See PC-500.
>
>
> I would stick to legitimate test equipment manufacturers, which
> needn't be that expensive as many are available very cheaply at
> hamfests today. The exception would be a serious oscilloscope-"simple
> scopes" can be had for five to twenty dollars all day and repaired by
> jackleg methods, but modern, calibrated, DC-coupled triggered sweep
> scopes with attenuators and calibrated sweep are probably best bought
> _new_. Or late model(still supported) refurb from legitimate test
> houses (i.e. not *ucker.)
>
> Fifteen years ago one was safe in saying "buy nothing but a Tek scope"
> but Tek does not build actual oscilloscopes, per se, today. Iwatsu in
> Japan is one of the last respoectable builders of scopes. Hameg in
> Germany may still be at it as well, but I don't know.
>
> People who "can't afford test equipment" are usually full of ****. And
> if they really aren't they need to get a job, or a better one at any
> rate. As the True Hams said in the old days,"If you have time to ham,
> you have time to build". (There are very, very few true hams left.)
>
Cal,
Tek's high end scopes are still made here. The ones assembled in China
are reported to have very good mechanical construction, and I'm sure they
didn't give the Chinese the responsibility of making the chips.

The best way to acquire a scope is to use eBay to purchase a used Tek
scope. The 7000 series are exemplary instruments, representing the finest in
American craftsmanship. The economics of maintenance are actually superior
to when these scopes were in production, as parts are plentiful through
cannibalization.
I personally have purchased a 7904 with a set of plugins for $170 off of
eBay, and it has worked flawlessly out of the box ever since. Many
specialized plugins are available for virtually any measurement need, from
low frequency differential to microwave sampling.
As for the odds of getting a bad one, I've bought around ten that way,
and never got bit. The scopes are well supported by the listserver TekScopes
>, who represent a wealth of expertise and
generous knowledge sharing.
A Tek 7000 scope equipped with the appropriate 7A21 differential plugin
can measure into the microvolt range, something a Hameg cannot. And when it
breaks, the superb documentation enables self-repair, or simply calibration.

[[email protected]]

The old Teks are lovely. My reluctance to invest money in them is due
to the lack of full support-there are chips and assemblies, plus the
CRT, that just are no longer available. For years I've hoped someone
would make replacement CRTs but it's not going to happen.

The new Tek scopes are all digitizing scopes with LCD displays. These
have many advantages but they do not, even with the "digital phosphor
technology", fully replace the analog CRT.

There are many fine Tek scopes out there from about a 30-year period
that are still good to use, and I don't mean to put off their buffs.
But they are just not supported by Tek anymore, and I don't want to
have to look at them when the jug, attenuators, or what have you fails
and it has to go to its final resting place.

It's interesting to note there is a company that-at ridiculous
cost-makes an aftermarket "mainframe" to allow 7000 series plugins to
be used with modern (or any other) scopes.

[Robert Morein]

> wrote in message
oups.com...
> The old Teks are lovely. My reluctance to invest money in them is due
> to the lack of full support-there are chips and assemblies, plus the
> CRT, that just are no longer available. For years I've hoped someone
> would make replacement CRTs but it's not going to happen.
>
> The new Tek scopes are all digitizing scopes with LCD displays. These
> have many advantages but they do not, even with the "digital phosphor
> technology", fully replace the analog CRT.
>
> There are many fine Tek scopes out there from about a 30-year period
> that are still good to use, and I don't mean to put off their buffs.
> But they are just not supported by Tek anymore, and I don't want to
> have to look at them when the jug, attenuators, or what have you fails
> and it has to go to its final resting place.
>
> It's interesting to note there is a company that-at ridiculous
> cost-makes an aftermarket "mainframe" to allow 7000 series plugins to
> be used with modern (or any other) scopes.
>

The parts are actually more available. How can you say a jug is not
available when every 7904 takes the same CRT as a 7704A, a mainframe that is
plentiful for $50?

Contrast this with the $500 (conservative) bill for a minor Iwatsu repair,
or the complete nonrepairability of any digital scope after the warranty
runs out.

Certain later Tek scopes should be avoided: the 2200 series and the 2400
series.
But the classic 7000 & 5000 series, and even the 500 series, are fine.

I have a Tek 555, built in 1961 or so, that I bought surplus from GE. It was
originally part of the Saturn V support project in Huntsville, AL. Every
time I turn it on, it works, unless it needs a tube. It has never needed
more.

If you really get stuck, Sphere in Canada has lots of Tek parts.