开云体育

Thanks. You beat me to the second question! I did wanna know if I
could "upgrade" knowing that better op-amps exist.

I've downloaded the book and will check it out later and added the
site to my Audio & Electronics Bookmarks.

Interesting note about "anything with banana plugs" is that when
playing around with the AM501 plugins was a sensitivity of the output
based upon the proximity of my hand near the jacks. Wild and crazy
things would happen as I got anywhere near 'em, sorta. One was much
more sensitive than the other.

Do ya have any recommendations for a replacement. I'd even be willing
to spend more than the few cents that some of these cost--maybe even
like $5--15 per chip!

: )

Thanks again.

Kuba Ober wrote:

> I guess for basic RF stage alignment you don't even need a scope, an
RF RMS
> voltmeter with a phase detector/indicator would probably suffice. I
used
> such a phase-indicating RF voltmeter back in high school to fix an
ailing
> RC receiver. It had a single mixer, an IF filter & amp, and it'd
directly
> demodulate the RF

I mean IF of course.

Kuba


You don't NEED anything like an RF RMS voltmeter. or phase detector. A
diode probe on a VTVM or very minimal scope will do just fine. You tune
for the typical 'rabbit ears' [flat phase] response.

Phase MIGHT be important in a wide band microwave communication system
using BPSK or QPSK or NPSK, but not in audio gear.

No way.

-John

My late father used to say "Why do it simply, when complicated works
well too" (It looses something in translation)

He also said "An engineer can do for two cents what any fool can do for
$10.00"

'nuff said,
-John



"DON CRAMER" wrote:

Oh sure you would have done that in the old days. But perhaps Kuba is
proposing
that with today's open source calibration code for radio and audio
alignment,
running under Linux in a home brew digital scope, anyone would of course
just dive
in there and modify the....

Or have I missed the point entirely yet again, Kuba? Drat, I hate it
when I do that.

Tee-hee. Thanks for the fun.

Hello,

Anyone have spares I have a way to test. I have three new 1000uf tabed
radials that have been tested and work in 465M, and one old style
1000uf OEM tested.

I also have one old style 18000uf tested good. I need either
replacements for the one 18000uf NOS or new or a couple of old styles
I can test.

Thankyou for all the help the two 18000uf new I purchased off ebay
turned out to be NG. I have access to a Sencor tester, willing to
horse trade.


Charles

On Wednesday 07 February 2007 16:49, you wrote:

Oh sure you would have done that in the old days. But perhaps Kuba is
proposing that with today's open source calibration code for radio and
audio alignment, running under Linux in a home brew digital scope, anyone
would of course just dive in there and modify the....

I don't have the clue what you're talking about :(

Er, guys, do you even know what you're arguing about? The discussion has
degenerated into everyone saying this: for a noob, buying an unknown 7603 and
having no access to equipment to properly test its performance is good
advice.

Given that "random" mainframes and plugins can perform pretty wildly, and that
a noob tends to believe what the screen shows, this is some bad advice
really. The OP ("noob") says that he needs the scope for audio work (among
other things). In audio work if you don't have other equipment such as
distortion meters or spectrum analyzers, the main ways to "align" anything is
to provide wideband square wave and tweak the stages till it looks right on
the output. Or to provide a sine wave input, and also tweak till you're
happy. If the scope does some of the things I had "random" 7603 + plugin
combinations do, good luck getting anywhere. The noob may well get completely
discouraged from furthering his/her interests.

So: getting a 7603 is a good thing, as it's an investment that can be built on
(more plugins) but it's a bad thing if you have nothing to at least partially
test and calibrate it with. Apart from the 7603, some good probes would also
be needed, especially for any RF tuning so that the probe doesn't detune the
DUT.

Kuba

I guess for basic RF stage alignment you don't even need a scope, an RF RMS
voltmeter with a phase detector/indicator would probably suffice. I used
such a phase-indicating RF voltmeter back in high school to fix an ailing
RC receiver. It had a single mixer, an IF filter & amp, and it'd directly
demodulate the RF

I mean IF of course.

Kuba

Oh sure you would have done that in the old days. But perhaps Kuba is
proposing that with today's open source calibration code for radio and
audio alignment, running under Linux in a home brew digital scope, anyone
would of course just dive in there and modify the....

I don't have the clue what you're talking about :(

Kuba

I was talking about "aligning" audio circuits, e.g. adjusting operating
points of various stages, checking response, etc. Not about any sort of
RF work.

If I wanted to see a nonlinearity of a stage in an audio power amp, for
example, it'd be nice to believe that the scope's vertical system is
linear enough, etc. Same goes for step response: hard to do with a scope
that may well distort even a perfect square wave.

Anyone who is at all capable of making those kind of measurements
would surely measure the input square wave first. If it looks like
a square wave, then the scope is good enough for the task.

The input will look like a square wave even with a badly nonlinear vertical
channel. The output "square" wave will then typically be much slower than the
input one you fed to your system. With nonlinear vertical, the slower
transitions on the output square wave will look distorted, and you may end up
chasing ghosts, especially if the audio amp alignment procedure mentions
e.g. "adjust Rxxx for output transitions to be smooth".

I just don't believe in using unchecked instruments, and a reasonable way to
check a 7603 with plugins is to use the classic calibration trio in a TM503,
plus a mainframe standardizer.

How on earth can anyone recommend using an unchecked, unknown scope to a newb
is beyond me. Newbs tend to misunderstand limitations of instruments they
use, so they are very likely to just blindly trust the trace, even if someone
experienced would check things twice first. You know, things like using too
much or too little of vertical deflection, not centering the signal and
hunting differing rising/falling edge aberrations, and so on. It's just very
easy to hit those on an uncalibrated scope methinks.

Cheers, Kuba

Kuba Ober wrote:

Given that IIRC the OP doesn't have a spectrum analyzer, you'll want to
get
step or pulse responses of the audio gear you're testing. I can hardly
see
that going all too well with an uncalibrated scope.

Audio "alignment" is essentially calibration work, and I can't see doing
that
with a scope that I know nothing about.

Have you ever ACTUALLY aligned a receiver?

I was talking about "aligning" audio circuits, e.g. adjusting operating points of various stages, checking response, etc. Not about any sort of RF work.
If I wanted to see a nonlinearity of a stage in an audio power amp, for example, it'd be nice to believe that the scope's vertical system is linear enough, etc. Same goes for step response: hard to do with a scope that may well distort even a perfect square wave.

Gee Kuba,

Anyone who is at all capable of making those kind of measurements
would surely measure the input square wave first. If it looks like
a square wave, then the scope is good enough for the task.

-Chuck Harris

On Wednesday 07 February 2007 13:56, you wrote:

Kuba Ober wrote:

Kuba wrote:

Well, if all you care about is *basically working*, then I agree. But
then you don't need a 7603 either. A random 7603 with random plugins will
*basically* work, but most of the time it doesn't really perform as a
dependable 100MHz instrument. Maybe it's my luck, but 90% of the plugins
that I bought in lots on eBay showed signs of being seriously
miscalibrated, and two of my mainframes (7603 and a 7633) were quite
miscalibrated as well; their pulse response was completely off limits and
you need the standardizer for that.

Cheers, Kuba

Kuba,

The origin of many instruments on eBay are government surplus, or surplus
acquired by someone with no calibration skills. In the first case,
metrology (instrument calibration) technicians in gub ment would screw up
an instrument they are trying to dump (or are instructed to do so) so it
gets tagged "unusable". The other case results from uneducated people
trying to fix something that ain't broke.

True, but given such a miscalibrated state, would you trust the instrument for
anything serious?

I guess for basic RF stage alignment you don't even need a scope, an RF RMS
voltmeter with a phase detector/indicator would probably suffice. I used such
a phase-indicating RF voltmeter back in high school to fix an ailing RC
receiver. It had a single mixer, an IF filter & amp, and it'd directly
demodulate the RF, if I remember things right. Due to vibration or whatnot
the two little coupling transformers had the slugs at all the wrong places,
and there was also a little air-wound coil with a couple turns that somehow
got distorted (maybe someone played with it too much) and needed bringing
back to shape. Being a total RF newb it took me a couple afternoons to figure
it out, but in the end I had it working. I had a scope, but all I cared for
was to get the response peak in the right place, and the voltmeter did just
that, and the scope's probe seemed to load the circuit too much. The
voltmeter had a couple different probes, two non-contact ones, and three
contact ones. I don't remember their specs, though. You needed one probe for
the voltmeter, and optionally another one for phase reference.

For non-RF-alignment work, e.g. audio amplifier design/testing/adjustment, you
will need to look at time-domain response, and for that you better had a
scope that's linear in both X and Y subsystems. How can one just assume that
it's the case with an unknown scope and not much to test it against??

Cheers, Kuba

Given that IIRC the OP doesn't have a spectrum analyzer, you'll want to
get
step or pulse responses of the audio gear you're testing. I can hardly
see
that going all too well with an uncalibrated scope.

Audio "alignment" is essentially calibration work, and I can't see doing
that
with a scope that I know nothing about.

Have you ever ACTUALLY aligned a receiver?

I was talking about "aligning" audio circuits, e.g. adjusting operating points
of various stages, checking response, etc. Not about any sort of RF work.

If I wanted to see a nonlinearity of a stage in an audio power amp, for
example, it'd be nice to believe that the scope's vertical system is linear
enough, etc. Same goes for step response: hard to do with a scope that may
well distort even a perfect square wave.

Cheers, Kuba

From: Kuba Ober

The original question was about a scope for audio and tuner alignment.

Given that IIRC the OP doesn't have a spectrum analyzer, you'll want to
get
step or pulse responses of the audio gear you're testing. I can hardly
see
that going all too well with an uncalibrated scope.

Audio "alignment" is essentially calibration work, and I can't see doing
that
with a scope that I know nothing about.

Cheers, Kuba



Have you ever ACTUALLY aligned a receiver? The most primitive scope
suffices. A 503 is overkill. Suggesting that it's akin to calibration is
audiophoolery. I guess you'd say you need a TDR to check your speaker
wires too.

All you have to do is get the IFs properly tuned (think diode probe flat
from 10.6 to 10.8 MHz) and get the RF stage (if any) to track the
oscillator properly. The trickiest part is the stereo circuitry and that
requires a special generator. A decent generator is FAR more important
than the scope.

-John

Kuba Ober wrote:

Kuba wrote:

Well, if all you care about is *basically working*, then I agree. But then you don't need a 7603 either. A random 7603 with random plugins will *basically* work, but most of the time it doesn't really perform as a dependable 100MHz instrument. Maybe it's my luck, but 90% of the plugins that I bought in lots on eBay showed signs of being seriously miscalibrated, and two of my mainframes (7603 and a 7633) were quite miscalibrated as well; their pulse response was completely off limits and you need the standardizer for that.

Cheers, Kuba

Kuba,

The origin of many instruments on eBay are government surplus, or surplus acquired by someone with no calibration skills. In the first case, metrology (instrument calibration) technicians in gub ment would screw up an instrument they are trying to dump (or are instructed to do so) so it gets tagged "unusable". The other case results from uneducated people trying to fix something that ain't broke.

Bill Roberts

A newbie may well not discern when someone is kidding and when not, and
may be too shy or something to ask for clarification. I prefer to be
straight forward than send someone off on a wild goose chase. YMMV.

I'd rather think that advising a newbie to buy an uncalibrated, unknown 7603
is sending him/her on a wild goose chase. A newbie will not have enough
experience to easily ascertain whether something is a scope issue or the DUT
issue.

Heck, I'd be uncomfortable using an off-eBay 7603 where all there is to test
it out is a 1kHz calibrator square wave.

Said newbie would do well to get some equipment to at least partially check
out the 7603, which really means a TM503 loaded with the amplitude
calibrator, time mark calibrator, and the levelled sine wave generator. Plus
requisite plumbing and attenuators. That's really the most basic setup. And
will cost approx. $500, depending on luck. The $1000 was a rough order of
magnitude.

Cheers, Kuba

The original question was about a scope for audio and tuner alignment.

Given that IIRC the OP doesn't have a spectrum analyzer, you'll want to get
step or pulse responses of the audio gear you're testing. I can hardly see
that going all too well with an uncalibrated scope.

Audio "alignment" is essentially calibration work, and I can't see doing that
with a scope that I know nothing about.

Cheers, Kuba

I would recommend the 7603 with a 7B53 Time Base and a couple of 7A18
Vertical Amps. You can get that combo for $125 or less. With the plethora
of other plug-ins available you would have a versatile system that is
easily repairable

Assuming you have approx. $1000 worth of other test equipment needed to
recalibrate said 7603 :)

It's an easily snowballing hobby.

NONSENSE: You can easily verify that a 7603 is basically working using
it's internal calibrator. and a length of wire For most work....
including the genesis of this thread... you don't need a lab quality
calibration. In fact, a 60 year old AC coupled DuMont would work just
fine.

Well, if all you care about is *basically working*, then I agree. But then you
don't need a 7603 either. A random 7603 with random plugins will *basically*
work, but most of the time it doesn't really perform as a dependable 100MHz
instrument. Maybe it's my luck, but 90% of the plugins that I bought in lots
on eBay showed signs of being seriously miscalibrated, and two of my
mainframes (7603 and a 7633) were quite miscalibrated as well; their pulse
response was completely off limits and you need the standardizer for that.

Cheers, Kuba

On Monday 05 February 2007 23:41, you wrote:

Beside collecting TM500 plugins, anyone actually usem, in particulars,
the AM501. Just got two of em.

I'd like to use a FG504 & FG501A plus other signal generators to
create all different types of waveforms. Integrating,
differentiating, ...

Any suggestions? Any neat experiements?

Specificatioins of the AM501? Comparisons with modern OP-Amps?

Anything that has got banana jacks on it *may* perform poorly for anything
above a few kilohertz due to parasitics, unless you put the feedback path next
to the chip. It does have a place to solder components inside, BTW. The
op-amp inside of AM501 can be replaced by a more modern chip, if you wish so.

The plugin itself was designed for teaching op-amps, and has little utility
beyond that methinks.

For source of great op-amp circuits, download this *excellent* book:

Applications Manual for Computing Amplifiers for Modeling, Measuring,
Manipulating & Much Else.


Then you'll want to get Troubleshooting Analog Circuits by Bob Pease, which
has an excellent section on real life op-amp behavior.

All in all, a good source of experimentation data is
, which has tons of analog computation
applications etc.

Cheers, Kuba

Hello Chris,
On A41 there is a chain from GND to +50V: R177 (35k7) - R176 (2k
trim, Shield Voltage) - R175 (12k7). The slide of R176 is decoupled
by C175 (0.01uF) to ground. Location R176 is what you said.
Calibration 9A Adjust Shield Volts:
a) Short vert.defl. leads together
b) DC meausure voltage on defl. leads.
c) remove short
d) DC measure pin 4 of P41U on the Z-axis board
e) Adjust R176 for approx. same reading as in b)
Success.
Albert

--- In TekScopes@..., "Christopher Hilton-Johnson"
<chj@...> wrote:

Greetings etc



I have a late model 7704A & an earlier manual. BAMA is no help.

Z axis board is suffix 01, my manual is for suffix 00.

Suffix 01 board shows an additional trim pot immediately below

R171, the Geometry trimmer.

Additional trim pot obscures the screen printed board ID, but I

think it is a variable version of R175 fixed @ 2k2 on the suffix 00
board.

Naturally my manual is silent on incorporating this variable into

the calibration process.

Can anyone help please?



Chris HJ


--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.432 / Virus Database: 268.17.25/669 - Release Date:

04/02/2007 21:58

[Non-text portions of this message have been removed]

Chris Johnson wrote:

Personally, I've always thought that the graticule should be an
overlay that's application specific and the CRT face is always clear,
so one tube type can be used in many products. But Tektronix tends
to go for the optimal solution for a given product rather than one
that's a little bit of a compromise. The integral graticule IS better.

If you go with an external graticule, the marking will be at least 1/4 inch
away from the phosphor. That leads to a rather nasty parallax problem.
Internal, or electronically drawn graticules are really the only way to go.

-Chuck

A lot of Tek CRTs are different only in how the graticule is marked.

For example, if it weren't for the fact that the graticules are
different, I could swap the pristine, very low hours CRT from my OF150
optical TDR into my 492 if I needed to. Fortunately, the 492's CRT
is in excellent shape. And I COULD do the swap, but the OF150's
graticule is graduated to 8 divisions by 8 divisions and the 492's
graticule is graduated in a 10 by 10 division pattern, and the
reference markers are different. It would be either very confusing
or you'd have to totally change the calibration of the analyzer if you
were to use the OF150's tube...if you wanted to be able to rely on the
graticule for any information, that is.


Personally, I've always thought that the graticule should be an
overlay that's application specific and the CRT face is always clear,
so one tube type can be used in many products. But Tektronix tends
to go for the optimal solution for a given product rather than one
that's a little bit of a compromise. The integral graticule IS better.



--- In TekScopes@..., <bhaskins@...> wrote:

I have often wondered about the actual differences in Tektronix CRTs.
Within a basic class the tubes appear to be identical except for the

part number.

Please cut me lots of slack on the word appear.
Just for example take the 465/a/b/m, 2213/3a/15/15a,and many others.
Quite some time ago, I got a nice 465B for almost nothing and it had

a dead crt.

I had almost nothing to lose so I tried a jug from a 465M which had

a badly

broken case.
It has been running fine for about four years now.
Any thoughts?