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
--
Dick
GM0MNL

"Dick" wrote
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:

"Dick" wrote in message
...
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
--
Dick
GM0MNL

"Nicholas O. Lindan" schreef in bericht
nk.net...

[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

--
Thanks, Frank.
(remove 'q' and 'invalid' when replying by email)

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

"Highland Ham" wrote in
:


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




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
jyanik-at-kua.net

"Highland Ham" wrote

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, 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/

In article et,
Nicholas O. Lindan wrote:


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.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

In article et,
says...

"Dick" wrote
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.

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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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

Dick wrote:

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
--
Dick
GM0MNL

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:

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