old TEK 475 problem

Yep, you're thinking along the right path. The broken connection that you're looking for is likely to be a tarnished or corroded vertical sensitivity switch contact in channel 2. Take the covers off the scope so you can get to the switch and see if you can get a cotton swab that has been dipped in 91% isopropyl alcohol, or denatured alcohol. Be careful not to get the common rubbing alcohol, because that may contain some contaminants that you don't want to leave behind. Scrub the contacts until they are bright and shiny. Actually, that's stretching it a bit.. just clean them until the areas that make contact are clean and tarnish-free. You might spray a cotton swab with a good tuner cleaner and CAREFULLY swab it onto the contacts. Be very careful not to get any of the lubricant that is in the tuner cleaner on the body of the switch. That's a pretty good scope, and cleanliness is important in this area. With a bit of care and luck, that should get your scope back into service. Good luck!! As for your probes, use Google to search for sources of used probes. I seem to remember a web site that specializes in used probes, advertising themselves as "dirt cheap probes" or something like that. Another great source for probes is at a hamfest, the larger the better. Find one that's scheduled within driving distance and visit. You'll probably find more than probes to spend your cash on. Cheers!!!

--
Tweetldee
Tweetldee at att dot net  (Just subsitute the appropriate characters in the
address)

Time is what keeps everything from happening all at once.

"Tweetldee" wrote in news:KHCXa.87843$ snipped-for-privacy@bgtnsc04-news.ops.worldnet.att.net:

Instead of using a cotton swab and getting cotton fibers wrapped around the contacts,use a narrow strip of clean white paper,slide it under the closed contact,then wet with a drop of alcohol(99% isopropyl).Then move the paper srtip back and forth to clean the contact and pad.Tedious,but effective,and you will not bugger up the contact fingers.Don't use tuner cleaner as some will attack the polypropylene PCB material,and some tuner cleaners also leave a lube film which is not good for TEK HF cam sw.contacts.(very low wiping force)

I'm an ex-TEK service person,21.5 yrs with TEK.

--
Jim Yanik,NRA member
remove null to contact me

Hmmm, what about NU-TROL control cleaner? It's tetrafluoroethane. Cleans like a champ, do you know if this can damage old Tek stuff? So far, it hasn't in my careful use of the stuff.

snipped-for-privacy@bellatlantic.net (Jeffrey Dutky) wrote in news: snipped-for-privacy@posting.google.com:

For new probes,

looks pretty good to me. I would think that you could repair the one you have.

r

--
"Any sufficiently advanced technology is indistinguishable from
magic."

Arthur C. Clarke (1917 - ), "Technology and the Future"

It could also be one of the compensation blocks that plug into the attenuator. I belive they are marked 2X, 5X and 10X. They way to tell is after doing the cleaning thing and if it doesn't fix the problem, swop the attenuation blocks from the good to the bad channel. Do one block at a time. Take Care, Kevin

-- change .combo to .com for correct email

*************************************************** "We ought always to know precisely why a given job is done in a particular way, and why it is done at all, and why it can't be done more efficiently, if it must be done at all."-- T.J.Watson

***************************************************

A E wrote in news: snipped-for-privacy@videotron.ca:

IIRC,we were told to avoid using TFE on the atttenuator PCBs.Supposed to cause microcracks in the substrate.

--
Jim Yanik,NRA member
remove null to contact me

Actually, it's a differentiator (high-pass filter), which says that the series capacitance is high in value (possibly open--totally capacitive) when compared to the shunt element (resistor || capacitor).

Thassaway to do it!

Far less damaging than cotton swabs.

If you want guaranteed pure isopropyl alcohol, go to a laboratory supplier and ask for "propan-2-ol", analytical quality. That won't have any nasty impurities in it.

--
Then there's duct tape ... 
              (Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

I'm not so sure this is good advice. I think this section of the 475 uses a very delicate cam switch which was only to be cleaned with pure methanol. You also don't want to get cotton fibers in there; they could stay behind and cause more problems, or snag the contacts and ruin the switch. Don't take my advice on this, you should see if your father had the 475 manual, because this will explain it all correctly.

There is something you CAN do right away. Rotate the vertical sensitivity knob back and forth a few times just to see if this helps at all. Move the AC-GND-DC switch back and forth a few times likewise; it should be on DC for the test above. Any of these switch contacts can get a bit of dust in there which could cause such a problem, so it's useful to find out exactly where the problem is before you start trying to clean things.

-

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

-----------------------------------------------

I was able to repair a bad attenuator block on one of my Tek scopes by resoldering the connections to the ceramic substrate. The plastic cover on the attenuator was easily removable. I'm not sure if the 475 uses the same type. In this case it was only some V/div that didn't work. If all settings aren't working I doubt it could be a bad attenuator.

--
Andy Cuffe
baltimora@psu.edu

I don't suppose you've got any tips on where I can obtain (electronically, if possible) a user manual & a service manual for my fantastic old Tek 2235 CRO? (It hasn't been calibrated in the 10 years I've owned it, but it still works beautifully!)

Lionel wrote in news:bgtovt$jhb$ snipped-for-privacy@pita.alt.net:

First,Ebay. Also; MANUALS SOURCES

TECH SYSTEMS 1-800-435-1516 SYNERGETICS SURPLUS 520-428-4073 PEPPER SYSTEMS 214-353-0257 MANUALS PLUS 206-531-8031 US SURPLUS 410-750-1083 E-MAIL: snipped-for-privacy@clark.net

Tektronix Used Manual Sources:

1. Deane Kidd 27270 SW Ladd Hill Road Sherwood, OR 97140, 503 625-

7363 (also has some parts)

1. Ed Matsuda, P.O. Box 390613, San Diego, CA 92149, 619 479-0225 voice, 619 479-1670 fax
2. Manual Merchant: Linda Perkins, PO Box 927792 San Diego CA 92192,

619-642-0785, -0885 fax, linda snipped-for-privacy@ix.netcom.com

1. W7FG Vintage Manuals, 3300 Wayside Dr., Bartlesville, OK 74006,

800-807-6146

1. Manuals Plus, P.O. Box 549, TAD #601, Tooele, Utah 84074, (801)

882-7188, (801) 882-7195 Fax

Some of these may be out of date.

--
Jim Yanik,NRA member
remove null to contact me

Not methanol, surely. It will probably attack the substrate, which is quite a special material (I forget exactly what, and I don't have the reference to hand). You'll notice that the attenuator PCBs are made of a different material to the rest of the vertical preamp PCB.

Methanol strips paint quite easily, and knocks hell out of some plastics.

Ethanol, maybe, if you can afford (or maybe make :-))) ) it. Else isopropyl alcohol.

--
Then there's duct tape ... 
              (Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

1st place I'd look is Tom Gootee (dead tree)

Try:

search "TM Title" for "tektronix" and scroll down to find the manual you're looking for.

Dino KLØS/4

I tried replying to the Grantl who asked for additional info but after removing the "NOSPAM" part of your address it still bounced. So here's the info on getting to the site:

---------- Grant-- try going first to:

Select "Publications and Forms"

which should get you to:

then select "Electronic Technical Manuals Online"

which will roll you down to:

"Go to Electronic Technical Manuals Online" - click on this link which takes you to:

If you accept their terms click on "I accept" which takes you to:

Choose "Enter the Site" [Note the disclaimer that you have to login if accessing anything but public release manuals and that you have to have 128 bit encryption engaged. That should bring you to:

which is the search page; click on "TM Title Text" and enter "tektronix" and scroll down to hit "search" which should get you to:

where if you scroll down and look CAREFULLY you'll find Tek 475 material which you can then download (it's in .pdf format).

You may have to go thru this entire process to establish the fact that you accept their terms....there's probably a cookie in my system that lets me go straight to the search page. I've found a number of good references here for text equipment.

Let me know if you have any luck...

Dino KLØS/4

Fred Abse wrote in news: snipped-for-privacy@cerebrumconfus.it:

Definitely not methanol!! We used isopropyl alcohol with no problem,ethanol such as medical or Everclear would work as well,although a bit more expensive.

--
Jim Yanik,NRA member
remove null to contact me

I admitted when I posted this that I wasn't sure of it, and that the poster should check his manual. I should have just done the same.

Indeed, the manual calls out isopropyl alcohol, especially for the vertical attenuation boards. They recommend using a camel hair brush, but I like Jim Y's suggestion of a strip of clean white paper.

Tek particularly advises AGAINST cotton swabs or "carbon-based solvents," by which I assume they mean carbon tet, etc.

-

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

-----------------------------------------------

One would assume so, but taken literally, it precludes isopropyl alcohol as well.

--
Then there's duct tape ... 
              (Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx