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: don@tinaja.com Please visit my GURU's LAIR web site at http://www.tinaja.com
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
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?" -----------== Posted via Newsfeed.Com - Uncensored Usenet News ==---------- http://www.newsfeed.com The #1 Newsgroup Service in the World! -----= Over 100,000 Newsgroups - Unlimited Fast Downloads - 19 Servers =-----
Have you cleaned the controls and switches? Electromechanical parts are the weakest link.
-- Joe Legris
"Dick" wrote
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:
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
You need the Tekscopes group: snipped-for-privacy@yahoogroups.com
Leon
"Nicholas O. Lindan" schreef in bericht news:5QXxd.7855$ snipped-for-privacy@newsread3.news.atl.earthlink.net...
[snip]
How true. Today I fixed something... all the way to the rubbish bin ;)
-- Thanks, Frank. (remove 'q' and 'invalid' when replying by email)
============================== 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
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!
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
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"Dick" schreef in bericht news: snipped-for-privacy@langwang.demon.co.uk...
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
"Highland Ham" wrote in news:mB_xd.352$ snipped-for-privacy@newsfe3-win.ntli.net:
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
Don Lancaster wrote in news: snipped-for-privacy@tinaja.com:
No.Use 99% isopropyl alcohol.
-- Jim Yanik jyanik-at-kua.net
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
John Miles wrote:
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
Jim Yanik wrote:
"John Miles" schreef in bericht news: snipped-for-privacy@news-central.giganews.com...
[snip]
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 ;)
-- Thanks, Frank. (remove 'q' and 'invalid' when replying by email)
I recently gave away a 465 that was giving me fits. I don't know what happened to it, but it had squirrelly problems all over. It was shipped to Tek for repair in the early 1990's and Tek said it was unrepairable. Of course I knew better.......
It was used extensively in field service, and was probably vibrated to death, but it had the damndest problems I ever saw. The ones that really killed me (other than the vertical attenuator switches) were an oscillation in the Ch 1 vertical, inability to get a smooth leading edge on a fast rise (fall was OK) and an intermittently failing intensified sweep. I spent about
100 hours on that thing and never did get it to work right. I don't know if that had multi-layer boards or not, but it acted like some inaccessible connections were intermittent. I checked and changed component after component, and there would always be one more trouble. That was my weekend for a few months; I would start and go througn the WHOLE calibration procedure (including the stuff that everybody skips, like swinging the line to check the power supply at high and low line conditions) to see how far I could get this time. Undoubtedly I would stop at some point because the adjustment didn't have enough range or some such. I'd fix that and next week a different set of stuff wouldn't work. The problems were never expensive stuff, just resistors and capacitors.That was the ONLY Tek scope that ever stumped me. I even managed to keep a
647 running, and those NEVER worked.Yes indeed. The perversity of the inanimate.
So I gave away the 465 and bought a TDS2012. Took a little getting used to, but I've never looked back. Still have the old reliable 547 and a whole slew of plug-ins in the corner, but they are going to need a new home before too long.
"Highland Ham" wrote
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/
"Roy Lewallen" wrote
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.
-- 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/
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