Tektronix 465 Scope

[Dick]

My Tek 465 scope has developed a minor but annoying fault in its
triggering circuitry but before diving into the guts of an old &
faithful friend I would appreciate it if anyone who has experienced
similar symptoms to those below could give me their thoughts on possible
causes & (more importantly) how they fixed their particular version of
the problem.

1) My scope just won't trigger in the A Normal mode although a stable
trace obtained in A Auto will remain displayed (and stable) in A Normal
until I touch either A Trigger slope or polarity controls.

2) I can stabilise a trace using the A Auto mode but only by adjusting
the A Trigger Hold-off control rather than the A Trigger slope/polarity
I would normally expect.

3) Everything appears to be triggering correctly when I use the B
Trigger.

4) All other scope functions appear to be OK.

I've checked these symptoms and they seem to be present what
ever type of signal I'm inputting - sine/square, 1kHz - 1MHz, Ch1 or
Ch2.

I've got a set of battered circuit diagrams & layout drawings so
should at least be able to follow up any ideas you experts might be able
to pass my way.

In the mean time many thanks for at least reading this posting
and Merry Xmas & Happy New Year to everyone fra' Auld Reekie

 

[Nicholas O. Lindan]

My Tek 465 scope has developed a minor but annoying fault in its
triggering circuitry

It sounds (reads) like a bad connection.

By Ole Occam's razor, and a description of the problem - 'it works
till I touch the knob' - my first guess is a dirty and/or worn
synch selection switch or trigger level pot. The pot wouldn't
happen to have one section for Ch. A and one for B and get
bypassed in Auto, would it?

If it were mine, I would first try a spritz of contact cleaner into
the switch via the front panel slot (IIR465C). All contact
cleaners are the same - mineral oil and alcohol - so the cheapest
Radio Shack stuff works as well as anything. WD40 also works well.

Getting to the switch or pot by disassembly I would save for last.
There is an old adage "Fix anything long enough and you will _really_
break it." And I wish I would remember that adage in time.

Other likely causes are bad connector, crimp or solder joint. After
that electrolytic caps.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

OP:

 

[Don Lancaster]

My Tek 465 scope has developed a minor but annoying fault in its
triggering circuitry but before diving into the guts of an old &
faithful friend I would appreciate it if anyone who has experienced
similar symptoms to those below could give me their thoughts on possible
causes & (more importantly) how they fixed their particular version of
the problem.

1) My scope just won't trigger in the A Normal mode although a stable
trace obtained in A Auto will remain displayed (and stable) in A Normal
until I touch either A Trigger slope or polarity controls.

2) I can stabilise a trace using the A Auto mode but only by adjusting
the A Trigger Hold-off control rather than the A Trigger slope/polarity
I would normally expect.

3) Everything appears to be triggering correctly when I use the B
Trigger.

4) All other scope functions appear to be OK.

I've checked these symptoms and they seem to be present what
ever type of signal I'm inputting - sine/square, 1kHz - 1MHz, Ch1 or
Ch2.

I've got a set of battered circuit diagrams & layout drawings so
should at least be able to follow up any ideas you experts might be able
to pass my way.

In the mean time many thanks for at least reading this posting
and Merry Xmas & Happy New Year to everyone fra' Auld Reekie

Clean the switches with Radio Shack tuner cleaner.

--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: [email protected]

Please visit my GURU's LAIR web site at http://www.tinaja.com

 

[Leon Heller]

My Tek 465 scope has developed a minor but annoying fault in its
triggering circuitry but before diving into the guts of an old &
faithful friend I would appreciate it if anyone who has experienced
similar symptoms to those below could give me their thoughts on possible
causes & (more importantly) how they fixed their particular version of
the problem.

1) My scope just won't trigger in the A Normal mode although a stable
trace obtained in A Auto will remain displayed (and stable) in A Normal
until I touch either A Trigger slope or polarity controls.

2) I can stabilise a trace using the A Auto mode but only by adjusting
the A Trigger Hold-off control rather than the A Trigger slope/polarity
I would normally expect.

3) Everything appears to be triggering correctly when I use the B
Trigger.

4) All other scope functions appear to be OK.

I've checked these symptoms and they seem to be present what
ever type of signal I'm inputting - sine/square, 1kHz - 1MHz, Ch1 or
Ch2.

I've got a set of battered circuit diagrams & layout drawings so
should at least be able to follow up any ideas you experts might be able
to pass my way.

You need the Tekscopes group: [email protected]

Leon

 

[Frank Bemelman]

"Nicholas O. Lindan" <[email protected]> schreef in bericht

[snip]

Getting to the switch or pot by disassembly I would save for last.
There is an old adage "Fix anything long enough and you will _really_
break it." And I wish I would remember that adage in time.

How true. Today I fixed something... all the way to the rubbish bin

 

[Highland Ham]

If it were mine, I would first try a spritz of contact cleaner into
the switch via the front panel slot (IIR465C). All contact
cleaners are the same - mineral oil and alcohol - so the cheapest
Radio Shack stuff works as well as anything. WD40 also works well.

==============================
On various occsasions I have been told that WD40 is NOT the right cleaning
agent for electrical systems involving plastic insulation re wiring, etc. I
always use (non chlorinated) contact cleaner as available from Rat Shack and
similar stores.
Here in the UK I use contact cleaner supplied by Maplin.

Frank GM0CSZ / KN6WH

 

[Joseph Legris]

My Tek 465 scope has developed a minor but annoying fault in its
triggering circuitry but before diving into the guts of an old &
faithful friend I would appreciate it if anyone who has experienced
similar symptoms to those below could give me their thoughts on possible
causes & (more importantly) how they fixed their particular version of
the problem.

1) My scope just won't trigger in the A Normal mode although a stable
trace obtained in A Auto will remain displayed (and stable) in A Normal
until I touch either A Trigger slope or polarity controls.

2) I can stabilise a trace using the A Auto mode but only by adjusting
the A Trigger Hold-off control rather than the A Trigger slope/polarity
I would normally expect.

3) Everything appears to be triggering correctly when I use the B
Trigger.

4) All other scope functions appear to be OK.

I've checked these symptoms and they seem to be present what
ever type of signal I'm inputting - sine/square, 1kHz - 1MHz, Ch1 or
Ch2.

I've got a set of battered circuit diagrams & layout drawings so
should at least be able to follow up any ideas you experts might be able
to pass my way.

In the mean time many thanks for at least reading this posting
and Merry Xmas & Happy New Year to everyone fra' Auld Reekie

Have you cleaned the controls and switches? Electromechanical parts are
the weakest link.

 

[Dave Platt]

By Ole Occam's razor, and a description of the problem - 'it works
till I touch the knob' - my first guess is a dirty and/or worn
synch selection switch or trigger level pot. The pot wouldn't
happen to have one section for Ch. A and one for B and get
bypassed in Auto, would it?

If it were mine, I would first try a spritz of contact cleaner into
the switch via the front panel slot (IIR465C). All contact
cleaners are the same - mineral oil and alcohol - so the cheapest
Radio Shack stuff works as well as anything. WD40 also works well.

Ugh. and Ugh again.

I'd raise three cautions about this advice:

[1] My recollection is that Tek specifically warns against using
most contact cleaners on, or around, certain of the internal
controls (e.g. the attenuator switches). These switches are
apparently quite sensitive to contamination, as they deal with
high-impedance signals. Spraying an oil-and-alcohol contact
cleaner anywhere in their area might very well contaminate them.

IIRC, Tek's recommendation is to use pure isopropyl alcohol, and
a small clean brush, for cleaning contacts.

[2] Not all contact cleaners are the same. Many used for sensitive
equipment are "zero-residue" types - they have a cleaning solvent
and propellant, but do not contain any sort of lubricant, and are
intended to leave nothing behind on the contacts. Even among the
contact treatments which do contain a lubricant of some sort, there
is wide variation in the type of solvent used (some use alcohol,
some use a hydrocarbon or chlorinated/fluorinated hydrocarbon)
and the lubricant used (some use mineral oil, some a polyphenyl
ether, others something else entirely). It pays to use the right
combination for the job.

[3] I would not use WD-40 as a contact cleaner, on anything less robust
than an electric motor. It's not formulated for that purpose
(in fact, it's not really formulated as a long-term lubricant!)
and it is notorious for getting gummy and attracting dust over
the long run.

 

[carel harmsen]

My Tek 465 scope has developed a minor but annoying fault in its
triggering circuitry but before diving into the guts of an old &
faithful friend I would appreciate it if anyone who has experienced
similar symptoms to those below could give me their thoughts on possible
causes & (more importantly) how they fixed their particular version of
the problem.

1) My scope just won't trigger in the A Normal mode although a stable
trace obtained in A Auto will remain displayed (and stable) in A Normal
until I touch either A Trigger slope or polarity controls.

2) I can stabilise a trace using the A Auto mode but only by adjusting
the A Trigger Hold-off control rather than the A Trigger slope/polarity
I would normally expect.

3) Everything appears to be triggering correctly when I use the B
Trigger.

4) All other scope functions appear to be OK.

I've checked these symptoms and they seem to be present what
ever type of signal I'm inputting - sine/square, 1kHz - 1MHz, Ch1 or
Ch2.

I've got a set of battered circuit diagrams & layout drawings so
should at least be able to follow up any ideas you experts might be able
to pass my way.

In the mean time many thanks for at least reading this posting
and Merry Xmas & Happy New Year to everyone fra' Auld Reekie

At the moment I'm having a fight with my Dynatek. So I looked up this
section in the schematics. Triggering looks simple. The trigger signal is
enabled/disabled by the outputs of a flipflop (LS74 here) which is
set/cleared by the channel selector switch. Here the switch is floating to
select Channel 2. So a bad contact will select channel 2. It looks almost
too simple, but an attack with contact cleaner may cure your old friend.

Carel

 

[Dr. Anton T. Squeegee]

It sounds (reads) like a bad connection.

By Ole Occam's razor, and a description of the problem - 'it works
till I touch the knob' - my first guess is a dirty and/or worn
synch selection switch or trigger level pot. The pot wouldn't
happen to have one section for Ch. A and one for B and get
bypassed in Auto, would it?

If it were mine, I would first try a spritz of contact cleaner into
the switch via the front panel slot (IIR465C). All contact
cleaners are the same - mineral oil and alcohol - so the cheapest
Radio Shack stuff works as well as anything. WD40 also works well.

NONONONONONONO!!!! DEFINITELY NOT!!!!!

All contact cleaners ARE NOT the same! Never have been, never will
be, and the proper ones for degreasing electronic equipment do NOT
contain any mineral oil!

I speak from knowledge gained over 25+ years of pro experience in
the fields of radio, electronics, and computers. NEVER, under ANY
conditions, use WD40 inside a Tektronix 'scope or any other electronic
device! It leaves an oily residue which will actually ATTRACT dirt and
gunge, and make the problem worse.

If you value your test equipment, don't cut corners on the stuff
you use to maintain it. Check the Tektronix service manual for the
recommended cleaner formulation, and get it from a quality electronics
supply place (Radio Shack does NOT come under that category as far as
I'm concerned).

I can tell you from personal experience that CRC 'CO Contact
Cleaner' works very well, and it is plastic-safe so you won't damage the
innards of the vertical attenuator assemblies.

It may cost a little more up front, or be a little harder to find,
but you won't be risking the long-term life of said equipment.

Happy hunting.

--
Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute.
(Known to some as Bruce Lane, ARS KC7GR,
kyrrin (a/t) bluefeathertech[d=o=t]calm -- www.bluefeathertech.com
"If Salvador Dali had owned a computer, would it have been equipped
with surreal ports?"


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[Roy Lewallen]

A number of the switches on the 465 use PC board pads as contacts. They
have heavy gold plating, but eventually the gold wears off. When that
happens, the switch is dead and as far as I know can't be repaired. You
might be able to squeeze a little more life out of it by cleaning, but
in any case I'd be very careful not to use a cleaner with any abrasive
qualities. If cleaning doesn't cure the problem, worn pads might be the
cause.

But by all means check with the 'scope newsgroup. I'm sure you'll find
folks who have had a lot of experience with the 465, and some might even
know of some kind of fix or replacement for worn switch contact pads.

Roy Lewallen, W7EL

 

[Jim Yanik]

==============================
On various occsasions I have been told that WD40 is NOT the right
cleaning agent for electrical systems involving plastic insulation re
wiring, etc. I always use (non chlorinated) contact cleaner as
available from Rat Shack and similar stores.
Here in the UK I use contact cleaner supplied by Maplin.

Frank GM0CSZ / KN6WH

On TEK LF or HF cam style contact switches,do NOT use mineral oil-based
cleaner/lubes.Take some 99% isopropyl alco,wet a narrow paper strip,and
slide under the closed contact,and move back and forth.These cam-style
switches have VERY low wiping force,and any oil,grease,or film will cause
intermittents or opens.

I suspect a calibration may improve his triggering,too.

 

[Jim Yanik]

Clean the switches with Radio Shack tuner cleaner.

No.Use 99% isopropyl alcohol.

 

[John Miles]

No.Use 99% isopropyl alcohol.

You know, it's funny how often these debates flare up over a subject as
mundane as contact cleaner. "My tuner cleaner is better than your tuner
cleaner. Your tuner cleaner should be used only in Ukrainian opposition
candidates' minestrone. My tuner cleaner costs more than HP printer
ink. If you spray your tuner cleaner on a Tektronix 465, it will
trigger a resonance cascade and gate in alien overlords from the planet
Xen." Yadda, yadda, yadda.

Despite all the gurus out there forking the evil eye at WD-40, I sure
seem to own a lot of stuff that still works fine after being sprayed
with WD-40 over the years (decades, in some cases). Yeah, I know.
"Data: n, plural of 'anecdote'."

Some of these gurus are admittedly respected veterans of companies such
as Tektronix, with whom mere mortals are loath to argue. All I can say
is, those switches must not have been of the greatest quality in the
first place, or the gurus wouldn't have to spend so much of their time
on Usenet warning people against hosing them down with WD-40.

Just sayin', is all. No disrespect intended.

-- jm

 

[Frank Bemelman]

"John Miles" <[email protected]> schreef in bericht

[snip]

Some of these gurus are admittedly respected veterans of companies such
as Tektronix, with whom mere mortals are loath to argue. All I can say
is, those switches must not have been of the greatest quality in the
first place, or the gurus wouldn't have to spend so much of their time
on Usenet warning people against hosing them down with WD-40.

LOL. Well, some switches on oscilloscopes are very fragile with many,
many contacts, and rather low contact pressure. Sometimes hermetically
sealed too, so you can even use a spray can of Spam or shaving foam and
it won't hurt a bit

 

[Roy Lewallen]

The discussion about contact cleaner isn't altogether mundane.

I worked at Tek for many years, although I'm certainly not a guru when
it comes to oscilloscope maintenance. But I do recall one experience
with cleaning solvents and board-mounted switches.

Before introducing a new instrument, we went through a lengthy process
of building and testing prototypes, which I described some time ago in
this newsgroup. In one group, it was our practice to borrow some
assemblers from production to build the prototypes. One afternoon I was
looking at some units they had built, after they had left for the day,
and saw that the plastic of some switch bodies was very badly crazed --
they were covered with tiny cracks. Some experiments with bottles of
solvent we found in some of the assemblers' work areas pinned it down to
one particular liquid. The problem was one of the ingredients, which was
a relatively common solvent of the time. Unfortunately, I don't recall
which one -- it was something pretty mild as solvents go, like toluene
or Freon, not a relatively strong solvent like acetone, which we all
knew better than to use. We found out that the solvent had been banned
from production, but the assemblers kept a supply out of sight because
it was really good at removing flux.

The lesson is that even some normally pretty innocent solvents can
destroy some plastics. Other components can also be ruined by various
solvents, so that's another reason to use some caution. As just one
example, it was found that Freon and its relatives would migrate up the
leads and into even pretty well sealed radial leaded aluminum
electrolytic capacitors, corroding the insides and causing premature
failure. This was solved by improving the end seals, but only after a
lot of the older type reached the field, some on boards having been
washed with Freon. Of course, Freon is no longer used, but there are a
host of other potential problems. It's ultimately up to you to decide
whether you want to experiment with your scope.

As for WD-40, I love the stuff and use it on all kinds of switches and
electrical components. But I mentioned a short while ago that the cam
switches in the 465 and some other scopes use PC board pads for
contacts, and when the pad's gold plating is gone, the switch -- and the
scope -- is dead. So it doesn't seem like a good thing to me to use a
cleaner on those that'll leave a film which can collect dust or anything
abrasive.

I don't agree that a switch's ability to withstand WD-40 or any other
particular chemical is an indicator of its quality. But we all have our
own criteria we use to judge.

Roy Lewallen, W7EL

 

[Nicholas O. Lindan]

WD40 is NOT the right cleaning agent for electrical systems
involving plastic insulation re wiring, etc.

That was also my impression. But I have used it on plastics and
have not found any problems after 20 years. Famous last words,
I know. I have used it as a contact cleaner with great success.

 

[Nicholas O. Lindan]

cam switches in the 465 and some other scopes use PC board pads for
contacts, and when the pad's gold plating is gone, the switch -- and the
scope -- is dead.

It is possible to re-plate the gold. But imagining the circuit board
it may be impossible to mask the components. Aw, what the heck - gold
plate the whole thing and screw it to your Hinkley yacht.

 

[Jim Yanik]

Some of these gurus are admittedly respected veterans of companies
such as Tektronix, with whom mere mortals are loath to argue.

I worked for TEK for 21.5 years as a service tech in 2 of their field
offices;repaired and cal'd a lot of scopes and other TEK products.

All I
can say is, those switches must not have been of the greatest quality
in the first place, or the gurus wouldn't have to spend so much of
their time on Usenet warning people against hosing them down with
WD-40.

Considering how longlasting and popular the 465 is,that's not a very smart
sentence.The same HF and LF cam switches were also used in the high-
performance 7000 series lab scopes.

Just sayin', is all. No disrespect intended.

-- jm

Same here.

 

[Roy Lewallen]

If there's any disagreement between what I say and what Jim says about
maintaining Tek scopes, listen to Jim and not me. He was there in the
trenches; I wasn't.

Roy Lewallen, W7EL