Favorite Tektronix Scope

[snip]

I've had that happen once. A competing company with nearly 20 staff quoted 1/3 what I quoted for a design job.

The potential customer said, "Something's fishy", and gave the contract to me.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Seconded. That microchannel plate CRT is a thing of great beauty. I used to use one with the Polaroid film plate on the front when I was a grad student.

They had a pretty nice analog storage scope whose number I forget--it was a portable and looked a lot like a 485.

I have an 11801A that I use all the time, with the 40 GHz sampling head. I got it for about a fifth of the cost of the overpriced modern version.

LeCroy is selling a 100 GHz sampling scope, which uses the Picosecond Pulse Labs 100 GHz sampler. Used to be that LeCroy made nice user interfaces but couldn't build a vertical amplifier to save their lives.

Cheers,

Phil Hobbs

Everything is relative. If you think the 454 is hard to work on, you should just SEE the insides of the 7000. Likewise the 7000 is a whole lot easier to work on than the latest generation of digital scopes.

If the switch wafers really are bad, the easiest thing to do is to use Cramolin with a very long spray tube. You can get it into very small places without having to do as much dissasembly. But make sure the contacts are tight, first. I don't see contact cleaning needed on the scopes of this era, although some of the older ones did.

--scott

--
"C\'est un Nagra.  C\'est suisse, et tres, tres precis."

On the basic Tektronix thread, I still have this Tek 650HR with a luminance problem. It appears to be the "PLRT INV & TRIG PICK-OFF" chip, which is a Tektronix 155-0216-00. Earlier revisions used a Tektronix 155-0032-00.

Tek says support for the monitor (and probably for the rest of the Group 26 products) was discontinued in 1996. They can't tell me what the original manufacturer's part number is, or even who the original manufacturer of the chip was, and the service manual lists only the house number.

Any Tek technicians happen to have some of these in the junk box, or know what the real part number is? The input that takes the base comparison voltage from the aperture pot is pulling the input way down.

--scott

--
"C\'est un Nagra.  C\'est suisse, et tres, tres precis."

I just had a 485 go flaky. I had to push on the front cover to get it to work. Is there a web site or a book that would help me get it going again?

Thanks PaulC

I just tracked down an intermittent in my 2467B's CRT supply, a process that would have been a lot tougher if I hadn't had both my 485 and 2430A clipped to various points. Scopes are cheap these days... you want at least three.

-- jm

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Note: My E-mail address has been altered to avoid spam

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I came across this on the 'net, which may or may not be useful in your particular case, John...

How to FIX the Fuzzy/Wide Trace on Your Tek 465 or 475 Scope!

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Cleaning the Volts/Div Attenuator Switch Contacts in Tektronix 4XX Oscilloscopes

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It might work wonders for your classic Tektronix 400-series scope. And you can probably do it yourself, even if you've never opened a scope, before! (C) Copyright 2004, by Thomas P. Gootee

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Here is a copy of the procedure that I sent to a guy with a Tek 475 that had a fuzzy trace, and "distorted" when he adjusted the volts/div knob. His original email is below, followed by my reply.

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--------- Original message -------- From: "Mike D" To: " snipped-for-privacy@fullnet.com" Date: 01-30-03 08:41

Do you repair scopes? I have a tek 475 that powers up but is very fuzzy and distorts when adjusting the volts/division knob.

I don't know if its worth repairing or if you can reccomend a better scope from your stock for a comparable price.

Thank You

Mike

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Mike,

Yes. I do repair *lots* of oscilloscopes. I do it mainly for in-house instruments that are to be resold. But, I also do it occasionally on a fee-for-service basis.

The symptoms you describe sound familiar and it sounds like a pretty easy repair job, which I could complete for $50. However, depending on your location, if you are in the continental USA, the shipping could be $20 to $30 or more, each way.

So, let me tell you what I would try first and maybe you can do it yourself. (I'd hate to see someone spend more than $100 for something that they might be able to do in less than 30 to 60 minutes.)

Without seeing the scope myself, I could easily be wrong. But, from your description, my opinion is that, most-likely, the switch contacts in the volts/div attenuators (and/or also in the trigger-view and bandwidth-limiter) are dirty or oxidized.

They are very easy to get to and to clean. And, although it might sound a little daunting to a first-timer, it really isn't difficult at all, requires only very-basic tools and supplies, and will probably work wonders for your scope's performance.

Here is the basic procedure:

Unplug the scope and place it on a large, flat, smooth surface, such as a table or floor.

Remove the scope's case: Start by removing the four screws in the rear panel's cord-wrap feet. They may be either Phillips-head or "star" (Torx) types. The feet may come off along with the screws. There are usually also two other screws, near the top and bottom of the rear panel, in the center. Remove them, too. After all six of the screws have been removed, rotate the carry-handle up and out of the way of the front panel, probably to the "straight up" position.

It is recommended that you stand the scope on its front panel end and pull the case up and off. But, if you DON'T have a front panel COVER, you can either try it anyway, hopefully on a padded surface (and carefully!), or else just leave the scope sitting on its feet.

From the rear of the scope, with your fingers on the sides of the case, push on the rear panel with your thumbs. If the scope is not standing on its front panel end, you will need to be very careful, as the scope slides out of the case, to also support the front end, keeping it up, so the bottom front edge of the case does not damage any of the internal parts of the scope by scraping against them.

Note that if the scope's CASE is DENTED, especially if it's dented on a corner-edge, it could be *VERY* difficult to remove the scope from its case! It might then require *QUITE* A BIT of brute force, pushing on the rear panel (or pulling on the edges of the front panel) and pulling on the rear edges (or pushing on the front edges) of the case. (Sometimes, in that situation, it helps to alternate between trying to move the left and right sides; and maybe even also to alternate between moving the top and bottom.)

After the scope is out (whew!), see the note in the next paragraph, and then carefully stand the scope on its SIDE, so that the vertical board, on the side of the scope, behind the v/div knobs, is facing UP.

NOTE! I usually try to lift and move the scope's internal assembly ONLY by the edges of the front panel (or CRT bezel) and rear panel, or other solid structural/steel parts. And be careful not to set the scope on any objects or uneven surfaces that might touch any of the internal components.

Just behind the volts/div knobs, inside the scope, there are two silver, metal "boxes", which house the attenuator/switch assemblies.

Remove all of the necessary screws to open the top of one of the boxes. (Do only one box at a time.)

Inside the box, there are four little rectangular, plastic "attenuator modules", each usually labeled with "somenumber X" (e.g. "4X"). Using a longnose pliers, or something similar (or whatever works), grasp one of them and pull *straight* up, to remove it. I'm not sure if they're static-sensitive, or not. But, just in case they are, I would lay it either on an all-metal part of the scope, or on a piece of aluminum foil, or something like that (i.e. on bare metal), with the pins facing down.

I usually only remove one attenuator module at a time, just so I don't get them mixed up. But you could do two at a time, if it's more convenient (which it often is).

While looking at the area of the circuit board where the attenuator module came from, rotate the corresponding v/div switch back and forth, until you can see which positions raise and lower the tiny gold U-shaped double-contact sets, up and down, from/to the circuit board.

Cut a small piece of clean, white paper, as lint-free as possible, into a thin strip, a little wider than one set of contacts, and long enough for you to handle/manipulate (probably something like three or four inches long and 3/16"-or-so wide?). Do not use cloth, which might snag, or anything abrasive. (You may need to cut new pieces, periodically, as you go through this procedure.)

Turn the volts/div knob, to raise the set of contacts that you're about to clean, up and away from the board.

Carefully slide one end of the paper under the contacts.

Apply a drop or two (or three) of isopropyl (rubbing) alcohol to the paper, under the contacts. It's OK to get it on the contacts, board, etc, too. I assume that the more concentrated the isopropyl is, the better. But I've had good results using the plain 70% drugstore type, and the 90% drugstore type. (The results would probably be even better if you use Caig's "De-Oxit" product, for the cleaning, followed by Caig's "Pro-Gold". They're available at Caig's Website.)

Immediately turn the volts/div switch so that the contacts are lowered against the paper and then (carefully!) pull the paper *straight* out from under the contacts. This should probably be repeated several times for each set of contacts.

Be careful. If you bend the contacts, you may be in trouble. And they are *quite* fragile. But, it should be fine as long as you try to pull the paper as parallel to the board as possible. Certainly, don't ever pull straight *upward* on it, and not even more upward than sideways.

Also, NOTE that a couple of the contact-pairs, the two that are nearest to the front of the scope, are raised and lowered by the AC/GND/DC lever-switch, instead of by the volts/div switch.

When all of the visible contacts have been cleaned that way, replace the attenuator module, carefully, by pushing its pins back into the holes in the circuit board and then pushing it all the way in. (It might not hurt to also clean the attenuator module's pins, although I've never needed to, nor tried to.)

[If you *DO* happen to have some of Caig's "De-Oxit" product, it might be good to apply a tiny amount to each pin of each attenuator block. I usually also apply it to the metal shield, wherever it makes contact with the screws or their mountings (and the the screw-posts/mountings themselves), and wherever the shield makes contact with any other metal surfaces, and also on those metal surfaces themselves. And the screws themselves should also be treated, as should any nearby "ground" screws (i.e. loosen, treat/clean, and re-seat). ALSO, make sure that you treat the grounding "spring" that protrudes up from one of the screws, where the crew touches it, and on its top where it touches the scope's case (and also do that part of the inside of the case). You can often SEE the difference in color of the metal, as the oxidation is removed, especially if you use the concentrated form of De-Oxit that comes in the small plastic "needle-dropper" bottle.]

Replace any attenuator modules that won't be in the way, any more. Then, remove the next attenuator module(s) and repeat the above procedures, until you've gotten to all of the switch contacts in the "box".

When one whole channel's switches are done, replace the metal cover over the attenuator/switch assembly and do the second channel in exactly the same way (or, what the heck, maybe *better*, if that was your first time...). [NOTE that the "fingers" that may be on one side of the shield/box need to go back into the same position that they were in before the top was removed.]

Now that you know what the tiny, gold switch contacts LOOK like, you will be able to much-more-easily find the SIMILAR ones that are on the SAME circuit board, but are toward the REAR of the scope, near the middle of the board. There is no cover over them. So they're MUCH easier to get to. There should be one group of four of them and another group of two of them. Moving the Bandwidth-Limiter and Trigger-View controls, on the front panel, will raise and lower them. Clean them in the same way as described above, for the attenuator switch contacts.

One OTHER thing to check: (I'm not sure, at the moment, if this is only for the 465 model, or if it also applies to the 475:) JUST behind the metal attenuator/switch shield "boxes", there may be a screw that connects a metal piece of the box/shield to the circuit board. If that screw is loose (which I have seen on about a third of the 465 scopes I've worked on!), or if it doesn't make good contact, you may see very noticeable effects in the trace(s), such as fuzziness or distortion, and may see trace-distortion effects when adjusting the trigger-level control (possibly especially-so at the highest frequencies), and possibly other triggering problems.

If cleaning the switch contacts doesn't fix the problems you're having with the "fuzzy" or wide trace, and the attenuator switch anomalies, further diagnosis and repair may be necessary.

Let me know if you try this, and how it works. If you would still like me to work on your scope, just let me know.

And let me know if I can be of more help.

Thanks again!

Best regards,

Tom

Tom Gootee snipped-for-privacy@fullnet.com

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"What is now proved was once only imagin\'d" - William Blake

You have two eyes don't you? [g]

My comment was based on what I have read. I have the service manual for the 454 and it is a well written book. The 454 is a a well designed scope, and parts are available. Fixing ANY high tech scope is NOT a job for the faint of heart, but at least the parts in the 454 are not so small (surface mount) that you need an electron microscope to see them! The older tube based tek's are what you want if you want to restore a scope yourself. However, if you want to buy a scope in working condition that you COULD fix yourself (OK substitute the word POSSIBLE for EASY) then the 45x series is about as "modern" as you want to go.

In the 1960s Tek did sell a switch servicing kit for the large dog kennel size 500 series models with wafer style rotary switches. I remember a pouch containing several bightly coloured pencil sized applicators of oil, grease and various cleaning fluids.

"Time to move on" Oh no! I would never get rid of an instrument for the want of a bit of effort. My 454 is now on the reserve bench as back up scope number 3 behind a couple of 465 scopes. My 454 has a nice clip on metal cover to protect the front panel. This is the scope I am more comfortable with lending to friends, knowing that the front panel is not going to get bashed in transit in the back of a car.

The slight intermittent problem with the timebase switch is minor, I can live with that. My 454 from the late 60s has big wafer switches just like the big 500 series scopes so cleaning these big wafer switches is easy providing you can get access to them. Access is the problem in the 454.

Bill Turner mentioned the U shaped contacts in the

465. Yes that was tricky tending to them but they are getatable. I would never dump a piece of test gear because of dodgy switches. I just don't have the heart to dump any test equipment. I should try and be stronger but I can't. Being a test equipment nut is a life crippling disease. :-)

Regards, John Crighton Sydney

"Too_Many_Tools" wrote in news: snipped-for-privacy@g43g2000cwa.googlegroups.com:

T921/22 or T932/35,hands down.

No TEK-made ICs,simple switches,low parts count,all solid-state. (excluding CRT,of course) Easy to access all parts of the scope,better than any other TEK scope..

--
Jim Yanik
jyanik
at
kua.net

snipped-for-privacy@panix.com (Scott Dorsey) wrote in news:dpc915$do8$ snipped-for-privacy@panix2.panix.com:

155-xxxx-xx and 234-xxxx-xx ICs were made **BY TEK**(they should have told you that),and they sold off the IC manufacturing unit to Maxim,who turned around and stopped making them,as TEK did not buy in the volumes Maxim wanted.

NO other company makes those 155 or 234 prefixed ICs.

The one good thing is that the 155-0032-xx was used in a lot of TEK products.You can find them in 465's,IIRC,on the trigger PCB. Try Ebay,or search electronic salvage companies that sell used TEK products.

I worked for TEK for 21.5 years as a service tech in their field offices,repairing and calibrating scopes,TM500,and TV test equipment.

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Jim Yanik
jyanik
at
kua.net

Don't you mean "not enough"? Two is sort of a minimum working level. 3 or 4 is nice to have! Can't beat the 465, 475, and 7000 series. Also use the 305x series when I need storage, math, or documenation.

--
Mark

Hello Paul, thanks very much for sharing those gems. I have stored them away.

I had a good laugh at your dining room table centre piece admisssions and the follow up doily and scope cosy remarks. Heh Heh heh.....

I must admit when I first got my 465 I just couldn't keep my hands off it and I had it covered up with a tea towel in between playing with it.

When you have lusted after something for decades and you finally get it. Oh what a feeling!

Regards, John Crighton Sydney

When would I need two scopes? What kind of practical situation? I am not desperate for money, but I am short of space. I am open minded regareing this issue.

i

Yes I agree everything is relative. An easy to repair comment should be defined a bit better, perhaps against time or compared against something else say removing a hard drive from a home conputer. Half a dozen screws and the cover is off, Pull two connectors and remove two or four mounting screws and the hard drive is out. I would call that easy. A job that takes less that 15 minutes I would say is easy.

I must admit I have never come across Cramolin. I will ask around. If it is available in Sydney, I'll find it.

Oh, I do! Going by the dates on the boards, I am guessing that my 454 was built around 1968 and has spent many years in someones backyard tin shed. The aluminium metal work is slightly pitted meaning it has been in a damp area. There was no filter for who knows how long, one or two decades maybe longer, so the insides are quite dusty.

Two years shy of forty years of age and the scope still works. Bloody marvellous! Switches in that environment of damp and dust can't be expected to remain clean and reliable. I am just amazed that my 454 scope works as well as it does even with its dodgy switch.

Regards, John Crighton Sydney

Oh well, I also wouldn't give up the Tek 454 I have. the best animal in the analog class. May be the only concurrent from Tektronis would be a Tek 2465. you can get one at about 0.6 kilobuck. very nice for the money, with one of the best triggering circuits I ever saw in 35 years in the field. Happy new year! Saandy 4Z5KS