Contact cleaner for TEK 465B?

I have a Tektronix 465B. I bought it used because it was one of the scopes recommended by folks who post here and on the electronics basic group. And I know hardly anything about oscilloscopes. It has worked very well until two days ago. The volts/div switch has one position where the display gets all wanky. I thinks that's the proper technical term. When any other position is chosen on the switch the display works perfectly. In the one bad position the display shows different types of wankyness as I wiggle the selector knob slightly back and forth. So I'm thinking about spraying some Deoxit D5 into the switch. I'll probably need to remove the scope cover to do this. Is this a bad idea? Is there a better solution? Thanks, Eric

Reply to
etpm
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"Cleaning the Volts/Div Attenuator Switch Contacts in Tektronix 4XX Oscilloscopes"

"Topic: Contact Cleaner and Switch lubricant"

"Tek 465 Cleaning" The recommendation of using WD-40 is controversial.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

I refuse to use WD-40 for anything on equipment other than removing adhesive residue.

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"I am a river to my people." 
Jeff-1.0 
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Reply to
Fox's Mercantile

I use Goof-Off, which is 25% to 50% mineral spirits. My thinking is anything that stinks that bad must be powerful stuff.

Wired Magazine send some WD-40 to a lab to check its composition. Mineral oil, decane, nonane, tridecane, tetradecane, dimethyl naphthalene, and cyclohexane. Mostly mineral oil, which is the primary ingredient of most commercial solvents, cleaners, and penetrating oils. The others are made from kerosene, naphtha, or stoddard solvent, which I consider to be fairly similar: For example, Caig Deoxit Gold is 75% "oderless mineral spirits": Bottom line: They're all basically the same stuff with a few additives.

All contact cleaners include a mild acid to remove the surface oxides from the contacts. In the distant past, Cramolin Red contained 95% naphtha and 5% oleic acid for the purpose. Oleic acid is food safe which makes it the ideal oxide remover. You can also get it cheap on eBay if you want to mix your own.

The problem with oleic acid is that it has to be removed after it strips off the oxides from the contacts or it will eventually corrode any exposed copper. That caused problems for Caig, so they removed it from the mix to be replaced with less aggressive oxide strippers.

Incidentally, if you also want an organically lubricated and smelling oscilloscope, a little olive oil, which is 55% to 83% oleic acid, might be an interesting substitute.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

Some cam switches I think I just used alcohol. I never did, pbut thinking of lube or cleaner lube, I love CRC 2-26.

Greg

Reply to
gregz

Yeah, don't use WD-40 on that. If you really MUST have a lube in there use LPS-2. Then of course give it a squirt of solvent.

I don't like ANYTHING about those switches. I understand why they did it but still just don't like them.

Good luck with it.

Reply to
jurb6006

Have a look in the service manual - it is online, or at least the one for the 475 is, and that is the same construction style.

I recall reading that because the contacts are gold, they don't tarnish and just need the dirt cleaned off, and would not benefit from any oily residue (as left by many contact cleaner sprays). Also, since they are open to the ventillation air, any oily residue will make dust stick to it and bring back the problem sooner than with just a cleaning.

I expect that the recommended cleaning solvent is probably some sort of Freon, but in the absence of that, pure isopropanol is probably ok.

The little contact forks that press against the PCB traces are very delicate, so don't touch them with hard objects unless you know what you are doing.

A problem that I had, with similar symptoms, is that the little attenuators are socketed, and I had dirty sockets on one of mine. Pulling out that attenuator and reseating it fixed it - the switches were not the problem that time.

There is a table in the service manual telling you which attenuators are switched in for which vertical volts/div setting. Using this table and your observations about the "wankyness" on each range, you could probably narrow it down to one attenuator, so that you have to mess with it in the minimum number of places.

Reply to
Chris Jones

Depending on the switch type, I use the following 'contact cleaners' from: Caig - Deoxit CRC contact cleaner Chemtronics contact cleaner, cleaner&lube LPS products

I will never let WD40 near any of my electronic stuff or mechanical stuff. Come to think of it, I don't let it near anything I work on.

For Tek scopes of that vintage, where lube is used, the original lube has d ried out. After cleaning (to remove the dirt & oxidation, as well as the o ld lube), it is recommended to relube it. Its been a while since I did thi s and don't remember what I used, but IIRC, the Tek SM cited the product.

There is a tek scope NG. If you post your question on there, I am sure you will get excellent pointers. Good luck J

Reply to
jjh

Thanks everyone for the replies regarding the cleaning of the switch contacts. I knew you all would come through with good info. Thanks Jeff especially for the links about cleaning these exact switches. I figured they would just be some sort of rotary switch. But they are more complex and take special care. Now that I have the info I am gonna use it to get the switching working correctly. And to avoid the rush I'll clean all the other switch contacts too. I guess a machine shop with oil mist in the air is not the best place for the scope to be stored. Who knew? I'll have to put it in the separate office. Eric

Reply to
etpm

Goof-off has n-methyl 2-pyrrolidone (NMP) in it, and that stuff goes through your skin super fast. It's not especially dangerous as organic solvents go, but still it's best to wear gloves.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Reply to
Phil Hobbs

Sorta, kinda, maybe. Goof-Off is the brand name, which includes a variety of products: I should have been more specific. I use Goof Off Gunk and Adhesive Remover:

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I use it for removing labels, not for cleaning switch contacts.

The MSDS shows no sign of NMP but does contain oleic acid, ethanol, ethylene glycol (anti-freeze), ether, limonene, and benzyl alcohol. One of these is probably as bad as NMP because when I use it without gloves, my hand still reek from the stuff and feel oily hours later, even if I wash my hands several times. I've also ruined at least two computer keyboards when the solvents removed the white lettering from the keycaps, even though I thought I had thoroughly washed my hands.

Goof-Off does make one product with NMP. Their Pro Stength Super Glue Remover contains NMP: There might be other Goof-Off products that use NMP, but I didn't feel like going through all the MSDS documents.

An EPA report on NMP use, mfg, distribution, processing, disposal, etc. See Pg 3 through 13 for other products that contain NMP:

As you mention, it doesn't appear to be very toxic:

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

I'll second the 2-26. It's the aerosol can I'd least like to do without for electronics work.

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Shaun. 

"Humans will have advanced a long, long way when religious belief has a cozy  
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Reply to
~misfit~

Ok, let's see what you get for your money with CRC 2-26:

Chemical Name CAS No % Distillates (petroleum), 64742-47-8 70 - 80 hydrotreated light Light mineral oil 8042-47-5 10 - 20 n-Butyl stearate 123-95-5 3 - 5 Fatty Acids, C18-unsatd, 61788-89-4 1 - 3 Dimers Petrolatum 8009-03-8 1 - 3

Nice job of obfuscating the actual contents, but the CAS numbers should produce something helpful.

Looks like it's mostly light petroleum distillate, which means kerosene (paraffin) or something similar. Kerosene can be both a solvent and a lubricant.

Light mineral oil probably means light mineral oil or white paraffin oil. Yet another lubricant.

n-Butyl stearate is a fatty acid based on zinc. It's food safe and kinda waxy. My guess is that it acts as a coating over the contacts to prevent further oxidation.

Fatty Acids, C18-unsatd, dimers. C18 would be oleic or possibly linoleic acid. I would guess linoleic acid which is a quick drying oil. It reacts with oxygen in the air to form a protective coating.

Petrolatum is another name for petroleum jelly or something similar. No clue what it's doing in the mix.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

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** OMG !!!

CRC 2-26 now comes in a big, plastic hand sprayer - like weed killer.

.... Phil

Reply to
Phil Allison

My first purchase was large can 12 oz. ? home Depot for about $4, then they just had smaller cans for MORE money.

Greg

Reply to
gregz

On Mon, 29 Oct 2018 19:03:50 -0700, Jeff Liebermann wrote: (...)

I have a guess(tm) as to why the petroleum jelly. It evaporates, but much slower than linoleic acid, which turns to goo as soon as it hits the air. That might clog the nozzle of the pump type spray bottle. Mixing with petroleum jelly should slow down the reaction so that it turns to goo after it's sprayed on the parts that needs lubrication or rust protection.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

The spray action is different from many aerosols. You can get a very controlled slow output that actually seems to bubble out. It covers parts nicely.

Greg

Reply to
gregz

Deoxit Gold - swear by the stuff since it helped us to get this going system again after 20+ years in a field with the doors open!

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Mike

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mail-veil

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