Topics

Clean and Lubricate Pots in Tek 475


Ed Breya
 

Regarding WD-40, I would not recommend it for small or fine parts and mechanisms, except as a last resort to free up things that are seriously seized up. On heavier machinery, it's great for a quick spray lube and freeing things seized up with rust and old grease - I use it copiously on my tractors. Someone mentioned that it leaves a residue that may get thick and sticky after time. I have noted the same, and I think it may be that some formulations of it (which have likely changed over the years) could contain vegetable or seed oils, for requirements like biodegradability. These non-mineral oils can be considered to be "drying" oils, which means they may eventually oxidize and polymerize into viscous plastic-like compounds. The most well known and quickest is perhaps linseed oil, but they all have the same tendency to "dry" over time, on exposure to air..I have used canola oil as a temporary non-toxic hydraulic fluid for our leaky pool cover mechanism, until I fixed it. Without knowing for sure what's in it, I'd say avoid WD-40 for electronics work. You don't want canola or peanut oil, say, in a pot.

As others have said, the WD-40 of today may be quite different from that of fifty years ago when recommended by Tek. I doubt that "biodegradable" was an official word back then, and WD-40 was probably a light mineral oil with solvents and additives. Anyone remember "Liquid Wrench?" That used to be my favorite in the old days.

Ed


Eric
 

With all the oils and lubricants being mentioned I feel I need to reiterate
something that is stated in the service manuals..DO NOT USE ANY lubricants
on the scopes high frequancy attenuator switch contacts these are to be
kept dry and the pcb will not tolerate anything but isopropyl alcohol on
them.

On Sat, Nov 7, 2020, 2:24 PM Ed Breya via groups.io <edbreya=
yahoo.com@groups.io> wrote:

Regarding WD-40, I would not recommend it for small or fine parts and
mechanisms, except as a last resort to free up things that are seriously
seized up. On heavier machinery, it's great for a quick spray lube and
freeing things seized up with rust and old grease - I use it copiously on
my tractors. Someone mentioned that it leaves a residue that may get thick
and sticky after time. I have noted the same, and I think it may be that
some formulations of it (which have likely changed over the years) could
contain vegetable or seed oils, for requirements like biodegradability.
These non-mineral oils can be considered to be "drying" oils, which means
they may eventually oxidize and polymerize into viscous plastic-like
compounds. The most well known and quickest is perhaps linseed oil, but
they all have the same tendency to "dry" over time, on exposure to air..I
have used canola oil as a temporary non-toxic hydraulic fluid for our leaky
pool cover mechanism, until I fixed it. Without knowing for sure what's in
it, I'd say avoid WD-40 for electronics work. You don't want canola or
peanut oil, say, in a pot.

As others have said, the WD-40 of today may be quite different from that
of fifty years ago when recommended by Tek. I doubt that "biodegradable"
was an official word back then, and WD-40 was probably a light mineral oil
with solvents and additives. Anyone remember "Liquid Wrench?" That used to
be my favorite in the old days.

Ed






 

Well, it's too late for me to not have used WD-40 now, but I'll take whatever comes.

The WD-40 seems to have done a good job of loosening up the channel #2 pot, but hasn't made much difference in the channel #1 pot (which is the worst of the lot in terms of stiffness and spring-back). The beam intensity pot is slightly loosened up, but its real issue is that there are spots along the first 1/3rd of its rotation where it produces maximum intensity (oddly, only when rotating the knob quickly).

From the schematic it looks like the intensity pot is a pull-down on the base intensity signal, so this would mean that the points of max intensity are points of no-contact (or very high resistance) in the pot. This could either be something that could be cured by cleaning, or it could be irreparably worn spots, correct?

I don't relish the idea of having to remove and replace the intensity pot, and I think I can live with the bad spots in the first 1/3rd. Replacing the channel #1 pot looks like it can be done without even removing the vertical amplifier board, so I'll do that if I can't get any improvement from an application of DeoxIT. I'm going to order all three of the replacement parts under any circumstance, in case of future need.

There are so many different products offered by CAIG Laboratories under the DeoxIT brand, I've already ordered a spray can of D5S-6 5% cleaner, but I was thinking of getting one of the oiler bottles 100% as well. Is one preferred over another?


Ed Breya
 

Yes, the attenuator boards are a special material - likely polysulfone - for good HF characteristics and low "hook," so don't risk damage with solvents or oils. Also, be very careful in soldering and unsoldering - the material easily melts or burns.

Ed


Ed Breya
 

Jeff, the bad spots on pots can likely be cleaned up by lots of rotations, even if you can't open them up or get enough oil or cleaner into them. Once you get the shafts to turn easily, rotate them end to end lots of times - possibly a hundred or more. For any particular bad spot, rotate the shaft lots more right around it, instead of the whole range, and see if it seems to improve.

This is approximately what many of us recommend - lots of rotations tend to eventually scrape off old grease and debris films on the resistor element. If the films are too tough, or the element is damaged, then there's not much else you can do but remove and fix or replace.

Ed


Greg Muir
 

Jeff,

Thank you for clarifying where the Tek recommendation for using WD40 is located. And I am glad that they stated its use for switch contacts – a completely different bird from potentiometers. There is not much to damage in a switch with lubricants unless plastic parts are not compatible with any possible added chemicals in the lube. And the caution mentioned by Eric regarding no application of lubricants to high frequency attenuator switch contacts is a very important thing to remember.

David,

I have found that WD40 has morphed into several different types of products these days including cleaners & degreasers, rust & corrosion inhibitors, roller chain lubes, and other stuff. While they still say that the composition in many of their products is “proprietary” and term their secret ingredient is aliphatic hydrocarbon I now see mention of other chemical terms as well in some of the newer products.

It appears that they now have labeled their traditional product “WD40 Multi-Use” and appears to have the same chemical composition with the above Aliphatic Hydrocarbons along with the usual “Petroleum Base Oil.”

Their “Electrical Contact Cleaner” consists partially of Heptane (which is not necessarily compatible with some plastics) and isopropyl alcohol.

And I agree with your position, David. Part of my work involves equipment reliability and along with that comes discretionary use of maintenance products to minimize any damage and increase operational lifetime..

Greg


 

Bill wrote:
Follow the instructions in the manual section on Vertical Preamp Circuit Board Removal. Make sure you have the correct manual for your S/N.
I had noticed that the service manuals available on eBay were all for "SN B250000 and up" and my unit is B219220. I have also found differences in the circuit images (not the schematics, the photographic images of the boards themselves) between the service manuals I downloaded from various web sites (475 Oscilloscope Service Instruction Manual, part # 070-1331-00), and the actual boards in my unit (specifically the arrangement of six resistors in front of the invert switch and below the first stage cascode amplifier for channel #2; in the manual they are arranged in a staggered vertical column, but on my unit they are rotated 90 degrees into a row, and the circuit traces are slightly different). I've also found differences in the specific part numbers (e.g. the manual specified part number 155-0085-00 for U120 and U220, the first stage vertical channel cascode amplifier, but my unit has part number 155-0085-01 for both of those parts).

I have not found a PDF of the "SN B250000 and up" manual on-line, but I'm wondering if my unit was upgraded in the field to the new vertical amplifier board (or maybe just had the vertical amplifier ICs replaced), or if there was an engineering change in the later units of the first run of the 475 (my unit was assembled in late 1974, so there was some time for Tek to have made changes).


greenboxmaven
 

WD-40 is acceptable as a part of a mechanical cleaning process. Flush it out with a correct solvent after it had done it's work. If it is left alone, it will form a residue that will be very difficult to remove.

Bruce Gentry, KA2IVY

On 11/7/20 3:05 PM, Jeff Dutky wrote:
Well, it's too late for me to not have used WD-40 now, but I'll take whatever comes.

The WD-40 seems to have done a good job of loosening up the channel #2 pot, but hasn't made much difference in the channel #1 pot (which is the worst of the lot in terms of stiffness and spring-back). The beam intensity pot is slightly loosened up, but its real issue is that there are spots along the first 1/3rd of its rotation where it produces maximum intensity (oddly, only when rotating the knob quickly).

From the schematic it looks like the intensity pot is a pull-down on the base intensity signal, so this would mean that the points of max intensity are points of no-contact (or very high resistance) in the pot. This could either be something that could be cured by cleaning, or it could be irreparably worn spots, correct?
I don't relish the idea of having to remove and replace the intensity pot, and I think I can live with the bad spots in the first 1/3rd. Replacing the channel #1 pot looks like it can be done without even removing the vertical amplifier board, so I'll do that if I can't get any improvement from an application of DeoxIT. I'm going to order all three of the replacement parts under any circumstance, in case of future need.

There are so many different products offered by CAIG Laboratories under the DeoxIT brand, I've already ordered a spray can of D5S-6 5% cleaner, but I was thinking of getting one of the oiler bottles 100% as well. Is one preferred over another?





 

Jeff:
The P/N 070-1332-00 is the manual you want. I see a pdf copy on Tekwiki at "http://w140.com/tekwiki/wiki/Main_Page". Then go to the 475 listing following the "400 Series Scopes" to the 475. Click on the "475" and that will take you to the page with several pdfs for the 475. I have the first one listed "Tektronix 475 Service Manual (65MB file, ok quality, PDF)" which may meet your needs. This should better match your S/N but I haven't looked at it completely. Artek manuals has a copy of the S/N 250000 and up for $7.50, if you download it. "http://artekmanuals.com/". Maybe by having both you can find the exact match to the boards you have in your 475?
The 465 that I have doesn't match exactly the manual I have for it even though it is supposed to be for the S/N that I have. But by looking at the manual for the next S/N range "B250000 and up" of the 465 I can see the boards that are in my unit. There are some "change" pages in the back of my 465 manual but not enough to cover some boards in my unit. So I don't know if someone did a "mix and match" to fix my 465 or if TEK did this at manufacturing. This 465 was not new to me so I don't have the manual that came with this unit. I do have the manual that came with my 475 because it was bought new by someone else and I got the manual from them along with the 475. I would have expected that your father would have had the manual that came with his 475 that you now have. But it could have been lost at sometime in the past?
I had a noisy intensity "A&B" pot in my 475 but I was able to remove the 4 screws and then open the pot up just enough to get a little Deoxid inside of the pot and then reassemble it with the 4 screws while it was still soldered to the PC Board. Taking that bottom PC Board out looks like a real nightmare. My intensity control works fine now.
Bill


 

Thanks for the pointer to Artek Manuals, I will go get a copy of that service manual straight away.

The 475 was originally a fleet instrument for my father's employer, but he got it as part of a somewhat odd severance package (the entire division was being dissolved/sold off, and he was one of the star employees). He may have gotten the service manual, or he may not have. If he did it is probably somewhere in his effects, which I have been making my slow way through during the pandemic. So far I have only found the operators instruction manual (and that only after I had bought the 475+DMM44 operators manual on eBay. The original 475 manual has a white cover; looks nothing like a Tektronix manual from the mid-70s. The 475+DMM44 manual has the nice blue cover and a little extra heft from the added section on making measurements with the DMM44).

Did Tek always ship a service manual with their scopes? I haven't found a 2213 service manual among my father's effects either, and he bought a fairly early one brand new, after he went independent, because it was so much easier to haul around than the 475. The only manuals my father had in the pouch for the 2213 were the manuals for the probes, and a copy of The XYZs of Using a Scope tailored for the 2213. If he got an operators manual or a service manual with the scope, he must have stored it somewhere else.

What you did is for your intensity pot is almost my exact plan as well. I don't think I can get at all four screws, but I figure if I loosen three of them then I might be able to get a 32G needle in the gap and inject some DeoxIT that way. There was some small improvement after I did the WD-40 thing, and it was enough to demonstrate that the beam intensity didn't really get visible until about 1/3rd of the way through the rotation, so all the dirty parts are actually in a range that I don't have much use for (maybe that low end of the range would be useful if I were using the Z axis input?).


 

Bruce Gentry wrote:
WD-40 is acceptable as a part of a mechanical cleaning process. Flush it out with a correct solvent after it had done it's work.
Would a "correct solvent" be isopropyl alcohol? I have access to a few other solvents, but some of them are explicitly forbidden in the Tek documents (e.g. Acetone) and at least one other (whether or not it's forbidden by Tek) is known to attack some common plastics.

An esoteric collection of solvents is another unusual feature of my father's effects which I have taken some pains to keep well sealed and safely stored.


Harvey White
 

On 11/7/2020 8:26 PM, Jeff Dutky wrote:
Thanks for the pointer to Artek Manuals, I will go get a copy of that service manual straight away.

The 475 was originally a fleet instrument for my father's employer, but he got it as part of a somewhat odd severance package (the entire division was being dissolved/sold off, and he was one of the star employees). He may have gotten the service manual, or he may not have. If he did it is probably somewhere in his effects, which I have been making my slow way through during the pandemic. So far I have only found the operators instruction manual (and that only after I had bought the 475+DMM44 operators manual on eBay. The original 475 manual has a white cover; looks nothing like a Tektronix manual from the mid-70s. The 475+DMM44 manual has the nice blue cover and a little extra heft from the added section on making measurements with the DMM44).

Did Tek always ship a service manual with their scopes? I haven't found a 2213 service manual among my father's effects either, and he bought a fairly early one brand new, after he went independent, because it was so much easier to haul around than the 475. The only manuals my father had in the pouch for the 2213 were the manuals for the probes, and a copy of The XYZs of Using a Scope tailored for the 2213. If he got an operators manual or a service manual with the scope, he must have stored it somewhere else.
From what I remember from looking through the catalogs, I do remember that service manuals *could* be an extra charge.  Once Tektronix combined the two (depended, I think, on the complexity of the manual), then that option went away.

Harvey

What you did is for your intensity pot is almost my exact plan as well. I don't think I can get at all four screws, but I figure if I loosen three of them then I might be able to get a 32G needle in the gap and inject some DeoxIT that way. There was some small improvement after I did the WD-40 thing, and it was enough to demonstrate that the beam intensity didn't really get visible until about 1/3rd of the way through the rotation, so all the dirty parts are actually in a range that I don't have much use for (maybe that low end of the range would be useful if I were using the Z axis input?).





Harvey White
 

Depends on what the solvent attacks.  Formula 409 and Simple Green can attack plastics because of some of their ingredients. Some solvents, Xylene, IIRC, attack plastics directly and will craze acryllic (for instance), or partially dissolve the base plastic.  Hence the problems.

Harvey

On 11/7/2020 8:31 PM, Jeff Dutky wrote:
Bruce Gentry wrote:
WD-40 is acceptable as a part of a mechanical cleaning process. Flush it out with a correct solvent after it had done it's work.
Would a "correct solvent" be isopropyl alcohol? I have access to a few other solvents, but some of them are explicitly forbidden in the Tek documents (e.g. Acetone) and at least one other (whether or not it's forbidden by Tek) is known to attack some common plastics.

An esoteric collection of solvents is another unusual feature of my father's effects which I have taken some pains to keep well sealed and safely stored.





Ray
 

There is on hail mary you can try.Drill a small hole sideways into the pot if it's made of plastic. You have to be steady or put a properly cut down brass tube over the drillbit to prevent drilling to deep. Then spray in your favourite lubricant.I did this on a icom transceiver and it worked nicely.RaySent from my T-Mobile 4G LTE device------ Original message------From: Ed Breya via groups.ioDate: Sat, Nov 7, 2020 14:29To: TekScopes@groups.io;Cc: Subject:Re: [TekScopes] Clean and Lubricate Pots in Tek 475Jeff, the bad spots on pots can likely be cleaned up by lots of rotations, even if you can't open them up or get enough oil or cleaner into them. Once you get the shafts to turn easily, rotate them end to end lots of times - possibly a hundred or more. For any particular bad spot, rotate the shaft lots more right around it, instead of the whole range, and see if it seems to improve.

This is approximately what many of us recommend - lots of rotations tend to eventually scrape off old grease and debris films on the resistor element. If the films are too tough, or the element is damaged, then there's not much else you can do but remove and fix or replace.

Ed


Eric
 

Hey Jeff isopropyl alcohol is probably one of the most used cleaners in
electronics. And yes stay away from acetone on tek gear it tends to eat the
plastics.

Eric

On Sat, Nov 7, 2020, 8:31 PM Jeff Dutky <jeff.dutky@gmail.com> wrote:

Bruce Gentry wrote:
WD-40 is acceptable as a part of a mechanical cleaning process. Flush
it out with a correct solvent after it had done it's work.

Would a "correct solvent" be isopropyl alcohol? I have access to a few
other solvents, but some of them are explicitly forbidden in the Tek
documents (e.g. Acetone) and at least one other (whether or not it's
forbidden by Tek) is known to attack some common plastics.

An esoteric collection of solvents is another unusual feature of my
father's effects which I have taken some pains to keep well sealed and
safely stored.






 

It looks like I was mistaken about what came with my father's 2213: I just found the printed copy of the 2213 Oscilloscope Operators Instruction Manual in a box with what looks like the other contents of the scope pouch (including the manual for the probes, assorted cables, wires, and components, all neatly bagged and labeled). In the front of the operators manual is the edge tag from what was clearly a perforated card. Handwritten on the tag is the note "Sent for Service Manual 8/24" which I must assume means August 24, 1981, because the front page of the manual reads only "First Printing JUN 1981" while the pdf version I downloaded from BAMA reads "First Printing JUN 1981, Revised AUG 1982". I guess this means I've got at least the 2213 service manual in some box in the attic or basement.

That probably means the chance of finding the 475 service manual, probably in the same box, has dramatically increased.