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Hi John:
I would like to take issue with you about the covers for the 49x analyzers. The original cover has two toggle actuated fingers that fit into the front flange of the instrument and hold the cover very tightly in place. The newer cover fits on with a friction fit and can come loose when banged around. Both covers are made from rather hard plastic material and will withstand very heavy impacts without breaking. If the instruments is packaged in a heavy box with firm plastic chusions, I can't believe that either cover could come loose and cause damage. With the cover installed, I can throw my 494AP in the back of the car or van and feel that the instrument is safe.
Now, to the original question, I have all ready posted an answer that I do not have either cover and I do not know of a source.
Deane

i wonder if the analyzers have some sort of high temp protection internally "thermostat"
alot of underhood automotive electronics is designed to run hot. "it does decrease its mtbf i dont care what the car makers say"
its the semiconductor junction temp that really counts not the heat sink temperature "i believe this"

Hi, Gerald --

Hi all,

I felt the rear if my Spectrum Analyser 492BP. I can not touch the
metal strip just above the plastic cover it's that hot. So I got out
my Fluke IR Thermometer and the surface read 56 Degrees C, wow.

I have discussed this with other people before, however it is now
summer down here and not being able to touch the rear in a hotter
climate is of real concern.

I just tried waving an IR thermometer around the back of my 494AP
after about two hours of operation, and the peak temperature I saw was
58C. Ambient temperature was approx. 27C in the room at the time.

I know you don't believe me, but that temperature level is fine. Quit
messing with it and have fun using it. :-)

Seriously: it is easy to do more harm than good by rigging up
additional fans or using a non-original replacement fan in these
analyzers. If you are not 100% confident in what you're doing, I'd
recommend leaving the hardware as-is. There is no problem to be
solved here.

-- john, KE5FX

Hi, Eric --

I have a 2754P spectrum analyzer that seems to function well
and is stable at all frequencies. However, when I try to run its
microprocessor's "Frequency Loops Cal" routine, the 1st LO seems
to be in a constant unlock state. Press shift to exit the cal mode,
and it immediately locks and behaves.

A few thoughts off the top of my head:

- What, specifically, suggests an unlocked first LO? Are you getting
specific error messages during self-calibration, or is it just hanging
in a loop?

- Is the unit thoroughly warmed up prior to calibration?

- When the calibration routine tells you to adjust various trimmers
and controls to bring the values within range, are you able to follow
the steps for all of the adjustments up until it starts telling you to
adjust the phase-lock assembly? (You'd normally hit SHIFT to end the
adjustment procedure at that point, unless you've been working on that
particular module.)

- Does the analyzer seem to work properly in both wide and narrow
spans? If so, how does its phase noise/sideband performance compare
with the 494P? The LO noise profiles should look identical, or at
least very similar to each other.

- Does it complete its front-panel-based self-calibration routine (CAL
button) successfully?

One very-common problem I have seen on these is failure of the crystal
oven in the 30 Hz/100 Hz IF filter mounted atop the CRT shield. The
series pass transistor inside the sealed filter overheats and opens
up, making the self-calibration routine either hang up or fail with an
error message during its final, narrowband sweeps. Even if you have a
separate LO problem, that is something you'll want to check. After
running for 20-30 minutes, the filter housing should be very warm to
the touch.

I check all the levels and swapped all of the 1st LO &
frequency control related modules between it and my 494P
(including the 1st LO YIG).

And the YIG interface board with the electrolytic caps, I'd assume?

All of the 2794 parts work in the 494 and none of the 494 modules fix
the 2754 cal routine.
Any thoughts or ideas? Has anyone experienced something like this
before?

Are the power supply voltages OK and within their ripple specs?

Which modules, exactly, did you try to exchange between the two?
(Don't forget the harmonic mixer, phase gate, counter, and auxiliary
synthesizer modules. Check the power connectors on the harmonic mixer
and phase gate, if you haven't already.)

-- john, KE5FX

Hello,

I have a 2754P spectrum analyzer that seems to function well and is stable at all frequencies. However, when I try to run its microprocessor's "Frequency Loops Cal" routine, the 1st LO seems to be in a constant unlock state. Press shift to exit the cal mode, and it immediately locks and behaves.

I check all the levels and swapped all of the 1st LO & frequency control related modules between it and my 494P (including the 1st LO YIG). All of the 2794 parts work in the 494 and none of the 494 modules fix the 2754 cal routine.

Any thoughts or ideas? Has anyone experienced something like this before?

Thanks, Eric

you believe the crest factor is so high that a modern true rms multimeter wouldnt do the job?
an iron vane voltmeter is true rms responding.
a chinese engineer told me the best true tms voltmeter for non super accurate measurements is a scope
read by a trained eye.
the best rms converter i know of is a thermal converter "thermocouple vacuum junction"

Hello Pierre,



If I remember right, the big iron potted case contains a device is called a
"saturable reactor" (or something like that) and is used to regulate the AC
voltage applied to the vertical amplifier tubes. I think this was an
attempt to minimize the effects of cathode interface which looks like a
spike on the leading edge of a fast-rise square wave. Actually, it is a
DECREASE in low frequency gain of the vertical amplifiers.



In a scope without regulated filament voltage, cathode interface is always
worse at low line voltages which means lower filament voltage and therefore,
lower filament temperature. If you observe a fast-rise square wave while
you lower the line voltage on a scope with bad cathode interface, the
leading edge spike seems to grow over about one minute of time. If you look
very carefully, it is actually the trailing edge, or flat portion of the
square wave, that is DECREASING in amplitude over time as the filaments cool
down. You can verify this by simply plugging in the scope calibrator and
watching the gain of the vertical change as the calibrator signal appears to
decrease in amplitude. No spike seems to grow on the leading edge because
there are no high frequency components in the scope calibrator signal.



There is actually a filament voltage adjustment in the 555 power supply and
the list of equipment needed to calibrate a 555 includes an iron vane AC
voltmeter to accurately set the AC filament voltage. I think the 517 is the
only other scope Tek made that has adjustable filament voltage . . . but I
could be wrong about this since it has been years since I looked at my
517's.



Stan



_____

From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of coresta
Sent: Saturday, December 30, 2006 11:53 PM
To: tekscopes@...
Subject: RE: [TekScopes] Re: Bringing up a 555



Hi Stan,

As i see this new thread, i always asked myself about the use of Kalotron in
the PSU of the 555 ? What's the big iron potted case too ?

I broke a pair of those PSUs many years ago and those are somewhere in the
basement . I never saw the schematic .

I have a 551 working that doesnt contain these parts .

Ah, happy new year to all of you !

And long life to our old old tubed scopes ;-)

Pierre

The 555 power supply uses that big heavy saturable reactor to
regulate the heater voltages. It relies on a little tube that varies
its conductivity according to the temperature of its filament and
varies the control current in the reactor, which in turn regulates
the heater supply transformers primary voltage.

And you are correct, the 551 did not have this arrangement.

Bonne Noel.

Larry Christopher





--- In TekScopes@..., "coresta" <coresta@...> wrote:

Hi Stan,



As i see this new thread, i always asked myself about the use of

Kalotron in

the PSU of the 555 ? What's the big iron potted case too ?



I broke a pair of those PSUs many years ago and those are somewhere

in the

basement . I never saw the schematic .

I have a 551 working that doesnt contain these parts .



Ah, happy new year to all of you !

And long life to our old old tubed scopes ;-)

Pierre

Andy,

Stan's right. I found a 555 on a dump, full of leaves and dirt. I stripped it down, cleaned all the waterproof bits in the bath, dried it with an airline followed by 3 hours at 60C. When I eventually got it all back together and switched it on, guess what? That's right - worked straight away.

It's worth the effort; these are lovely bits of engineering.

Richard.


Stan and Patricia Griffiths wrote:

Anyone have any source available for TM system blank plates, or the eject
button only?



/Lars



-----Ursprungligt meddelande-----
Fr?n: TekScopes@... [mailto:TekScopes@...] F?r
jones_chap
Skickat: den 31 december 2006 13:16
Till: TekScopes@...
?mne: [TekScopes] DP501 Schematic & Parts List Please



Looking for DP501 Parts List & Schematics. Anyone have it in pdf,
html, or djvu format? If so, please email to me. If larger than
maybe 10MB, encoded, then send to mlcgray@bellsouth.
<mailto:mlcgray%40bellsouth.net> net.

I'd really like to take a look at this plug-in!

Thanks.





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

Found @ BAMA! ;) 4mbyte djvu file. A beautiful scope btw.





-----Ursprungligt meddelande-----
Fr?n: TekScopes@... [mailto:TekScopes@...] F?r
jeep534
Skickat: den 31 december 2006 12:42
Till: TekScopes@...
?mne: [TekScopes] new to me 310 A scope



I have just aquired a 310A scope SN 023989 and I would like to find
the manuals for it. it is in unknown condition. I would like to clean
it up and use it. Hopefully I can get it to work properly ( with a lot
of help from you guys of course)

Happy Hunting
archie =) =) =)





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

Looking for DP501 Parts List & Schematics. Anyone have it in pdf,
html, or djvu format? If so, please email to me. If larger than
maybe 10MB, encoded, then send to mlcgray@....

I'd really like to take a look at this plug-in!

Thanks.

I have just aquired a 310A scope SN 023989 and I would like to find
the manuals for it. it is in unknown condition. I would like to clean
it up and use it. Hopefully I can get it to work properly ( with a lot
of help from you guys of course)

Happy Hunting
archie =) =) =)

First, does there exist a front cover for the 492 Spectrum Analyzer,
and, if it does, where can I get one ?

You'll see them on eBay every once in awhile, or for that matter,
Deane Kidd may be able to put his hands on one. There is an older-
and a newer-style (all plastic) cover; either will fit.

The innermost surface of the newer covers have a cool Easter egg
(raised thermoplastic signatures of several dozen Tek employees from
the spectrum-analyzer product group). The foam-rubber liner will most
likely be in better condition in these as well.

Other than that, they will both work OK. They are really just dust
covers, though. Under no circumstances should you ever ship a
49x-series analyzer with either front cover in place. The older-style
covers are likely to come loose and bash the heck out of the front
panel. The newer-style covers are lighter, but their flexible plastic
latches are prone to breakage if any force is exerted on them during
transport.

-- john, KE5FX

Hi Stan,



As i see this new thread, i always asked myself about the use of Kalotron in
the PSU of the 555 ? What’s the big iron potted case too ?



I broke a pair of those PSUs many years ago and those are somewhere in the
basement . I never saw the schematic .

I have a 551 working that doesnt contain these parts .



Ah, happy new year to all of you !

And long life to our old old tubed scopes ;-)

Pierre





_____

De : TekScopes@... [mailto:TekScopes@...] De la part
de Stan and Patricia Griffiths
Envoyé : dimanche 31 décembre 2006 03:10
? : 'faustian.spirit'
Cc : TekScopes
Objet : RE: [TekScopes] Re: Bringing up a 555



Hi Andy,

You asked about connectors for extender cables. There are three possible
extenders you could be talking about: 1) vertical plugin, 2) timebase
plugin, 3) power cable from mainframe to power supply. I am sure I have
connectors that I can sell you to build extenders for either type of plugin
for a couple of dollars per connector. Most of what I have have been
salvaged but are still perfectly useable. In the Tektronix Service Center
we had an extra long power supply cable that made it much easier to turn the
555 on its side for maintenance. Let me know if you need some connectors to
make extenders.

You also asked me how many old scopes "blew up" :-) on turn on. No
explosions that I can recall, but some came quietly on but did not work
completely.

Stan

_____

From: TekScopes@yahoogrou <mailto:TekScopes%40yahoogroups.com> ps.com
[mailto:TekScopes@yahoogrou <mailto:TekScopes%40yahoogroups.com> ps.com] On
Behalf
Of faustian.spirit
Sent: Friday, December 29, 2006 6:38 PM
To: TekScopes@yahoogrou <mailto:TekScopes%40yahoogroups.com> ps.com
Subject: [TekScopes] Re: Bringing up a 555

--- In TekScopes@yahoogrou <mailto:TekScopes%40yahoogroups.com> ps.com,
"Stan and Patricia Griffiths"
<w7ni@...> wrote:

Hi Andy,



Others may call me careless in my approach to firing up an old 555,

but I

would just plug it in and turn it on. It is pretty well fused and I

would

not expect any to blow anyway.

Probably will soon... Visual inspection shows nothing suspicious at
least... I could put the L and CA in, but now I feel obliged to at
least try to recalibrate or fix the D (was marked "broken" but seems
to work except that the gain is too low and the CMRR is lousy... Most
of the switch trouble vanished after applying some Tuner 600) ...
whoever designed it had money in the plugin extender business I guess
:) And something with the idea of operating a 500 series lying on its
side strikes me as very odd... same with sawing a hole in the table...

Are the connectors needed to make an extender cable as rare as those
in the 551/555 PSU cable are said to be? I noted the pitch is
different....

You can not test the power supply disconnected from the scope and your
reason is correct. It must have a proper load on it and, yes, you

will need

all plugins in place to put a proper load on the power supply. Both
timebases and both verticals.



On old Tek scopes, I never bother to reform the electrolytics. A

shorted

one is very rare and an open one will show up as too much ripple

somewhere.

I have never seen a shorted one do serious damage.



Over the past 46 years, I have probably turned on more than 1000 of

these

old scopes. I have lost count but I have at least six or seven

555's in my

collection . . . maybe more.

How many blew up? :)

I think when originally shipped from the factory, the serial number

of the

power supply will match the serial number of the mainframe.

Sometimes in

the field, mainframes and power supplies get swapped around, but I can't
remember any serious incompatibility problems, even with mismatched

serial

numbers.



Stan

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

the arrl handbook is too basic for that.
i think the ee programs are more theoretical at an undergraduate level then they were 40 yrs ago
i have about 2 yrs of college but have never taken an "electronics" class.
they just taught me about "i" and how to integrate and differentiate
alot of advanced math is quite simple once you understand the concepts and models.
we live in a wonderful time where we can throw away our slide rules , log tables and hand held calcs
and let a computer crunch away on stuff for us.
many engineers designed complex stuff mostly using compiled tables and graphs
and then tweaking their designs until they worked "good enough"
thats what test equipment is used for in engineering.
to prove theoretical designs

Here are some measurements on my 494P. After about 3 hours of operation in its normal position (45 degrees tilted up on the handle, standing on the floor inside a wood rack without much air circulation), the hottest part of the metal case on the back panel was slightly over 60 degrees C. The hottest point is to the left of the instrument, when looking over the top standing in front of the instrument. On the right side, the temperature was about 5 degrees lower.

The winner is the HP 5370A, where the exposed rear heat sink reaches over 66 degrees C while the instrument is in open air. Ambient temperature in the shack was about 26 degrees C at the time these measurements were made.

In both cases, the line voltage was very close to 115 VAC (it fluctuates +/- a volt around 115 typically.)

Didier KO4BB


Gerald wrote:

The winner in my collection is the 517 at 1250 Watts.



Stan

Hi Andy,



You asked about connectors for extender cables. There are three possible
extenders you could be talking about: 1) vertical plugin, 2) timebase
plugin, 3) power cable from mainframe to power supply. I am sure I have
connectors that I can sell you to build extenders for either type of plugin
for a couple of dollars per connector. Most of what I have have been
salvaged but are still perfectly useable. In the Tektronix Service Center
we had an extra long power supply cable that made it much easier to turn the
555 on its side for maintenance. Let me know if you need some connectors to
make extenders.



You also asked me how many old scopes "blew up" :-) on turn on. No
explosions that I can recall, but some came quietly on but did not work
completely.



Stan



_____

From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of faustian.spirit
Sent: Friday, December 29, 2006 6:38 PM
To: TekScopes@...
Subject: [TekScopes] Re: Bringing up a 555



--- In TekScopes@yahoogrou <mailto:TekScopes%40yahoogroups.com> ps.com,
"Stan and Patricia Griffiths"
<w7ni@...> wrote:

Hi Andy,



Others may call me careless in my approach to firing up an old 555,

but I

would just plug it in and turn it on. It is pretty well fused and I

would

not expect any to blow anyway.

Probably will soon... Visual inspection shows nothing suspicious at
least... I could put the L and CA in, but now I feel obliged to at
least try to recalibrate or fix the D (was marked "broken" but seems
to work except that the gain is too low and the CMRR is lousy... Most
of the switch trouble vanished after applying some Tuner 600) ...
whoever designed it had money in the plugin extender business I guess
:) And something with the idea of operating a 500 series lying on its
side strikes me as very odd... same with sawing a hole in the table...

Are the connectors needed to make an extender cable as rare as those
in the 551/555 PSU cable are said to be? I noted the pitch is
different....

You can not test the power supply disconnected from the scope and your
reason is correct. It must have a proper load on it and, yes, you

will need

all plugins in place to put a proper load on the power supply. Both
timebases and both verticals.



On old Tek scopes, I never bother to reform the electrolytics. A

shorted

one is very rare and an open one will show up as too much ripple

somewhere.

I have never seen a shorted one do serious damage.



Over the past 46 years, I have probably turned on more than 1000 of

these

old scopes. I have lost count but I have at least six or seven

555's in my

collection . . . maybe more.

How many blew up? :)

I think when originally shipped from the factory, the serial number

of the

power supply will match the serial number of the mainframe.

Sometimes in

the field, mainframes and power supplies get swapped around, but I can't
remember any serious incompatibility problems, even with mismatched

serial

numbers.



Stan

Hi, Gerald
Dont know in what part of Aussie you be, but over here in the West we are
often plagued with
higher than normal Line Voltages, specially if u live near an industrial
area
or near a feeder transformer / substation

No doubt u have already checked this , but just in case check yr own line
voltage
preferable with a true RMS meter or known caiibrated (standard AC) average
reading one
Test the line waveform too. Generally its a good enough sine wave but I
have seen
line waveform distortions in some of the places ive been that u woudn't
believe!

Check out that the 492P is on its max line taps (if it has such a selection)
and not
just on 220V.
Does it get so hot all the time, or only in the evenings? If the latter it
coulf be that
industrial area shut downs around knock off time leave an uncompensated line
voltage too high

For these very reasons my own GP bench in Perth is ran from a metered step
down auto transformer
with selectable taps and my test bench outlets from a number of AC
stabilizers to keep RMS
line volts to 220v with good AC waveform
If all this seems obvious and u are well aware of it all, my apologies, but
I have ran into
the same issue myself in the past and others with similar problems may
benefit

Whats the ambient temp in yr shop /room ? Probably an external fan is a good
idea anyway
in our ever warming climate for those items of lab gear really intended to
work
in a protected lab environment (not that ime saying the 492P is)

Of course,you could have a fault with the 492P that others are better
quailfied to comment
on but the above seems a good place to start.

Hope yr 492P gives u years of trouble free use. Happy new year

John (hpxref)