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Clean and Lubricate Pots in Tek 475


 

The vertical position pots and the beam intensity pot on my Tek 475 oscilloscope are stiff and scratchy. The service manual says that they are pre-lubricated and sealed, and that no regular lubrication or cleaning is necessary, but I think that this may not still be true 50 years after the unit was manufactured.

I can see that the pots have four screws on the opposite end from the control shaft, but I'm not sure what I would have to do to clean and lubricate the pots once I had them open. Also, the pots in question (part #s 311-1397-00 and 311-1533-00 seem to actually be two pots connected to together, in the case of the first pot, which is used for the vertical input position adjustment, they are two 5K Ohm pots, and the second pot, which is the bean intensity adjustment is one 5K Ohm and one 2.5MegOhm pot).

I've already searched for replacement parts, and have found some promising leads, but I would rather clean and lube the pots in-place than have to unsolder anything (which would require significantly disassembling the scope in order to get at the backside of the circuit boards).

Does anybody have experience re-lubricating these pots, and could tell me what I'm up against?


Simon
 

Some have had success dribbling IPA on the pot shafts with a hypodermic syringe and turning the shaft from stop to stop many times. It helps if the scope is positioned vertically to benefit from gravity.
For calibration you can look through the steps in the service manual, and work out how long that would take with the specified test instruments, then factor in a technician’s labor. It would probably work out more than the scope is worth. They can be picked up for about $250 on eBay and maybe twice that for a fully refurbished one. You can adjust the timebase fairly easily with a crystal controlled function generator, but the vertical amplifier calibration requires more sophisticated instrumentation. My function generator has a TTL output and I swapped the 74LSXX output IC for a 74HCXX and could measure a 5 ns rise time on 10 ns/div so I was happy with the frequency response, but I never got both Y amps the same. To calibrate them, page 75 of the service manual gives you the list of instruments required. It is rather daunting.
It seems a nice idea to restore it to its original factory state, but unless you plan to use it in your job it is probably not worth it.
Simon


Ed Breya
 

First try lubing the pot shaft bushings from outside - remove the knobs, and give them a generous drenching with light oil, then rotate them lots of times (put the knobs back on if necessary). This should loosen them up. Also push and pull on the shafts (they will only move maybe a few .001 inches axially) to help get some oil in, and loosen the crust and gum. If the pots then turn freely, rotate them a bunch of more times to clean up the elements. If after all this, the pots are still binding or noisy, then you may need to take them apart for internal cleaning. If you don't get immediate improvement, let them sit overnight and try again before taking more drastic measures.

Ed


 

tenareze32 wrote:
It seems a nice idea to restore it to its original factory state, but unless you plan to use it in your job it is probably not worth it.
Absolutely true. This is just for a hobby, and for nostalgia (it belonged to my late father). Even for the hobby work I don't think I need it fully calibrated, as long as it's not wildly wrong it should be fine for my needs, but if I could get it properly calibrated for under $300 then I would consider it.


 

Ed Breya wrote:
First try lubing the pot shaft bushings from outside - remove the knobs, and give them a generous drenching
with light oil, then rotate them lots of times
I tried this straight away, and it seems to have eliminated the "spring-back" in the vertical position pots, but they're just as stiff as ever. The intensity pot has some kind of "scratchiness" in it's first 30% of rotation, and that hasn't been affected much at all by lubrication either, but now it's clear to me that the trace is simply too dim to be seen for the first 15-20% of the pot's rotation, so I'm not too concerned.

As you say I will let them sit overnight and see if things change.

The sources I've found on-line have the pots for very reasonable prices, so I guess if worse comes to worst I can always replace them (no matter how daunting it appears to be to get the boards out to unsolder them). If they loosen up overnight, however, I'll take the win.

It's been quite therapeutic to be able to make even minor repairs to this instrument, and to discover that it was not imminently going to destroy itself because some part had worn out from age or disuse. Even if it's not operating 100% perfectly it's still a wonderful scope, delightful to use, and more than adequate for my purposes.


Eric
 

Jeff contact me off list and we can see what we can work out on the
calibration. But tek them selves is a calibration option as well I called
them about a 465 a while back and they quoted me $100.00 for a factory
calibration.

On Fri, Nov 6, 2020, 7:16 AM Jeff Dutky <jeff.dutky@gmail.com> wrote:

Ed Breya wrote:
First try lubing the pot shaft bushings from outside - remove the knobs,
and give them a generous drenching
with light oil, then rotate them lots of times
I tried this straight away, and it seems to have eliminated the
"spring-back" in the vertical position pots, but they're just as stiff as
ever. The intensity pot has some kind of "scratchiness" in it's first 30%
of rotation, and that hasn't been affected much at all by lubrication
either, but now it's clear to me that the trace is simply too dim to be
seen for the first 15-20% of the pot's rotation, so I'm not too concerned.

As you say I will let them sit overnight and see if things change.

The sources I've found on-line have the pots for very reasonable prices,
so I guess if worse comes to worst I can always replace them (no matter how
daunting it appears to be to get the boards out to unsolder them). If they
loosen up overnight, however, I'll take the win.

It's been quite therapeutic to be able to make even minor repairs to this
instrument, and to discover that it was not imminently going to destroy
itself because some part had worn out from age or disuse. Even if it's not
operating 100% perfectly it's still a wonderful scope, delightful to use,
and more than adequate for my purposes.






 

You are describing the "A & B" (Allen Bradly) pots. I just got through going completely through my 475 after years of putting up with attenuator "leaf springs" not making good contact and the vertical and intensity pot problems you are seeing in you father's 475. I removed the vertical board preamp board and unsoldered these A&B pots from the PC board. I then removed the 4 screws and completely took these vertical position pots apart. I put a little Deoxid into them and tried to find the problem with the stiffness and the "springback" of these pots with little success. For some reason I could not locate why they turn ok when apart BUT are stiff when assembled. Fortunately I had picked up a "parts" 475 some years ago for fixing up my 475. The parts 475 had Bournes installed in this unit in all of the areas of vertical position, brightness, horizontal position, astigmatism, focus and so on. So I bit the bullet and did the work necessary to change the Bournes pots into my 475. This requires removing the necessary PC boards in some cases and is a pain in the ass. I see a seller on the bay that is selling the 311-1397-00 vertical pots that are brand new. I would suggest strongly that you buy these and save yourself a lot of grief in the long run. He also has the horizontal position pot and others for this scope. Now my 475 controls work just like they did from the factory and intended. I don't know why the A&B pots fail years later. The A&B pots seem to be used in the early units and then the Bournes in the later units. Maybe because A&B went out of business?
But after cleaning the gold contacts in the attenuators and generally cleaning up this area I am now very happy. Do the work and you will be happy with the results.
Bill


Ed Breya
 

Yes, getting the pots out may be the hardest part, whether you refurbish them or replace them. Again, I don't know how accessible they are, but at least they're on the periphery of the front panel. If the pots are those square black or blue "modular" type, with screws on the back, they can easily be opened up for cleaning and re-lubing. Just keep track of all the pieces as you go, and how they need to fit back together. Some of these pot types are riveted together rather than held with screws. Even these can be worked over by carefully drilling out the ends of the rivets, and replacing them with 2-56 screws, long enough to go through the assembly.

If it is just too much grief to get the pots out, and soaking the bushings isn't enough, there other tricks to help with getting more oil into them. If you have a well stocked parts/junk department, you may have some "pot spacers," which are typically hollow hex tubes of various lengths, threaded the same as the pot (1/4-30 or 1/4-32 I think). These are commonly used in equipment to recess pots behind the front panel. If you find one, you can remove the original pot nut, and thread the spacer on in its place, just a little more than hand tight. Then put the scope on its back with the front panel up, and flood the spacer with oil and let it soak overnight. If this is still not enough, the next degree is to do vacuum assist, if you have any kind of vacuum source available. It just has be rigged up to put suction on the temporary oil reservoir that you made with the spacer. If you can get decent vacuum on it for maybe a few seconds to a minute, some air from inside the pot should bubble up through the oil, and then pull some more oil in after the vacuum is released. This can be repeated a number of times. The pots are not truly "sealed," and will gradually leak everywhere, so any pressure difference is only temporary.

If you don't have any pot spacer hardware, you can do the same with a piece of rubber or plastic tubing, but it's trickier to attach. You want a tight fit, so the tubing is deformed and self-threaded onto the pot, to minimize oil and air leakage.

An alternative to vacuum is to put air pressure on instead, to force some oil into the pot. As you can imagine though, this could get quite messy - especially if you have a blowout in the tubing attachments.

Ed


Greg Muir
 

Be careful using oil on a potentiometer. I have seen some pots where oil has loosened the binder holding the carbon to its surface and ruined it. In addition oil works wonderfully to capture contamination causing future problems.

This is why control cleaners are manufactured specifically for cleaning & lubricating pots & switches. The lubricants contained in these products are formulated not to cause additional problems. WD40 and solvents of an aggressive nature are not made for electronic applications such as this.

Greg


Ed Breya
 

On Fri, Nov 6, 2020 at 10:05 AM, Bill wrote:


I put a little Deoxid into them and tried to find the problem with the
stiffness and the "springback" of these pots with little success. For some
reason I could not locate why they turn ok when apart BUT are stiff when
assembled.
It depends on the particular construction, which may vary a lot between brands. styles, and grades. If you refurbish a pot and it still binds after thorough cleaning and lubing, look at all the possible parts that can deform with age and use. First, make sure the shaft isn't bent, which is especially possible on 1/8" and smaller ones. Next, check the axial end play. It should be able to move in and out at least a few .001" at any rotational position. If not, then the whole thing is just too tight, likely due to any rubber and plastic parts deteriorating or cold-flowing.

The definition and construction of a "sealed" pot varies. Fancier, better grade ones may be more elaborate and include rubber gaskets between parts, and a rubber shaft seal like an o-ring at the bulkhead, or on a neck cut in the shaft. This is what tends to give the "springback" feel, due to deterioration and swelling of the material. If you can find a fresh o-ring equivalent to the original, replacing it should fix that problem. An alternative is to just delete the o-ring - the benefit of the seal isn't that big a deal anymore, in a benign hobby/lab environment. If the o-ring is at the bulkhead, eliminating it will likely also increase the axial play, possibly too much. You can try a thinner o-ring or add appropriate shim washers to tweak it.

If there are no shaft seals, then look at any rubber gasket layers - the rubber gets thinner over time under compression, so the whole assembly gets shorter, reducing axial clearance inside. If there is a shim washer at the bulkhead, you can try a thinner one or deleting it, but be aware the shim is also part of the thrust bearing function, so the pot may run rougher without it. If you can't effectively shorten the rotor assembly, then you can lengthen the body by say making new gaskets with thicker or fresh material, or adding shim washers between sections, around the screws. Again, high grade environmental sealing is not that important anymore.

If there are no rubber parts at all to blame, then cold-flowing of the plastic body parts is the likely cause. Study the construction and look at all the options to either shorten the insides, or lengthen the outsides.

Ed


Eric
 

Greg i have to disagree with you on this one. Tektronix them selves used to
have a product called "no noise" this was actually replaced with wd40. A
can of wd40 actually has a tektronix part number. The tektronox part number
is 006-2574-00.

Eric


On Fri, Nov 6, 2020, 3:25 PM Ed Breya via groups.io <edbreya=
yahoo.com@groups.io> wrote:

On Fri, Nov 6, 2020 at 10:05 AM, Bill wrote:


I put a little Deoxid into them and tried to find the problem with the
stiffness and the "springback" of these pots with little success. For
some
reason I could not locate why they turn ok when apart BUT are stiff when
assembled.
It depends on the particular construction, which may vary a lot between
brands. styles, and grades. If you refurbish a pot and it still binds after
thorough cleaning and lubing, look at all the possible parts that can
deform with age and use. First, make sure the shaft isn't bent, which is
especially possible on 1/8" and smaller ones. Next, check the axial end
play. It should be able to move in and out at least a few .001" at any
rotational position. If not, then the whole thing is just too tight, likely
due to any rubber and plastic parts deteriorating or cold-flowing.

The definition and construction of a "sealed" pot varies. Fancier, better
grade ones may be more elaborate and include rubber gaskets between parts,
and a rubber shaft seal like an o-ring at the bulkhead, or on a neck cut in
the shaft. This is what tends to give the "springback" feel, due to
deterioration and swelling of the material. If you can find a fresh o-ring
equivalent to the original, replacing it should fix that problem. An
alternative is to just delete the o-ring - the benefit of the seal isn't
that big a deal anymore, in a benign hobby/lab environment. If the o-ring
is at the bulkhead, eliminating it will likely also increase the axial
play, possibly too much. You can try a thinner o-ring or add appropriate
shim washers to tweak it.

If there are no shaft seals, then look at any rubber gasket layers - the
rubber gets thinner over time under compression, so the whole assembly gets
shorter, reducing axial clearance inside. If there is a shim washer at the
bulkhead, you can try a thinner one or deleting it, but be aware the shim
is also part of the thrust bearing function, so the pot may run rougher
without it. If you can't effectively shorten the rotor assembly, then you
can lengthen the body by say making new gaskets with thicker or fresh
material, or adding shim washers between sections, around the screws.
Again, high grade environmental sealing is not that important anymore.

If there are no rubber parts at all to blame, then cold-flowing of the
plastic body parts is the likely cause. Study the construction and look at
all the options to either shorten the insides, or lengthen the outsides.

Ed






 

Ed:
The A&B pots were designed to be modular. What I mean by this is that they are designed to fit together such that you can make a 1,2,3 section, or probably more, multiple pots out of the sections. The 311-1397-00 is one example of what Tektronix did with these. So you start with a front module that has the shaft and is the "thread" end of the assembly. Then you just add the first variable resistor section which fits into the front shaft section and mates with the "driver" on the rear of the shaft section which is also "keyed" so that you cannot assemble these incorrectly. Then the second variable resistor section is designed to "mate" with the first variable resistor section with a little driver piece to provide the link between the first resistor and second resistor shaft. There are no "rubber" gaskets between the resistor sections in this design. Then this can continue until you have the number of sections you need. A&B obviously made resistor sections in different resistance values so you could make up a control with say 5K in the first and 10k in the second and so on. I have no idea exactly what values A&B made available. Then there is a back plate where the 4 screws go through to the front shaft section in the front and hold the whole assembly together.
I found that each resistor sections would turn very easy and the front shaft was turning easily also, but when the whole assembly was put together it was stiff and springy. I tried to find the source of the stiffness with no success whatsoever. I left the screws loose and still no relief. The back section shaft was not touching the rear plate so no problem there. You cannot disassemble the individual sections but it is easy to get the Deoxid into them and that got rid of the "scratchiness". These controls were not stiff and springy at the beginning when I got the 475 in 1980 or so but something inside of each resistor section must somehow add up to the whole problem. I also tried to clean each section in IPA and then reassemble but to no avail. I then tried to "lubricate" the section shafts with the same results. I guess what I could do is destroy one section by "tearing" it apart by force and see what is inside of the section shafts to see what A&B put inside. These are the black pots.
The newer Bournes pots are riveted together and must be factory ordered as to the resistance values you need for each section. These are the blue pots. A little research told me that Bournes bought A&B sometime in the past. The shafts of the A&Bs were not bent in any way and were connected to the front panel of the 475 with the usual fiber shafts that Tek liked to use when the pots were mounted on the PC boards way back in the instruments. The Bournes are an exact replacement in the PC board after removal of the older A&B pots, as you would expect.
There is NO way to remove the vertical position pots in the 475 vertical preamp board without removing the board from the instrument. Then it is easy to unsolder them from the PC board and work on them.
Bill


 

Bill,

I had a closer look at the vertical input board and it looks like it might come out with less work than I thought. I haven't verified this, but it looks like the BNC connectors might not be mounted to the front panel (I thought I read a blog entry about repairing a 475 that said something about this, but I can't it now, however this post of EEVBlog shows a full teardown, which seem to support my hypothesis <https://www.eevblog.com/forum/projects/tektronix-465-repair-and-restoration/>;). If that's true, then getting at the two vertical position pots is much easier (if not quite trivial). I also noticed that the only pots that got stiff are the "double stack" ones. The single stack, which appear to be from the same manufacturer, are all easy to turn.

It looks like I can buy replacements for between $10-$20 per pot, which I think is a fine price. If I can get the vertical input and main boards out without too much fuss, and if just lubricating them doesn't help, then I will just replace them.

I'm not sure who made these pots, but all of them (with the possible exception of the two trigger level pots, which are metal cans rather than plastic blocks) are brown/black plastic with dark red inserts. The replacements I've found online (from talonelectronic.com and rshopboss.com) are blue, and my scope was assembled in late 1974, so I'm assuming that it has A&B pots.

I have been very happy with the results I've gotten so far with what I consider fairly minimal effort: I only had to break out the soldering iron ONCE on this old thing, and that was completely unavoidable; to replace a obviously very dead electrolytic capacitor on the sweep board.


 

Here is the link that says that removing the vertical amplifier board is not as involved as you would expect it to be (though I'm not sure I understand exactly what he is saying is involved in removing the attenuator switch assembly): https://entertaininghacks.wordpress.com/2018/02/27/renovating-a-tektronix-475-timebase-switches-potentiometers-and-hf-response/

This also covers most of the problems I've been seeing. It's an excellent post.


Greg Muir
 

Eric,

I am aware that there are various camps regarding the use/not use of WD40 as a cleaner & lubricant for potentiometers. I myself shy away from it given past experiences with the behavior of this penetrant/lubricant and it’s properties over time.

There has been much said about the combination of the carrier and lubricant used in this product and its propensity to leave behind residue after the carrier evaporates. In my experience I have witness a very heavy and sticky form of oil that forms after extended periods of time.

Aside from that I adhere to products listed as being specifically formulated for electronic purposes. In many respects it is better to be safe than sorry especially if the target item is non-replaceable as those things used in legacy equipment. Granted Tek did specify (or recommend) WD40 in a couple of their documents but it was not widespread. This was possibly due to a recommendation made by one or a few individuals. Although I do not know where these recommendations were made I feel that the factory designed service lifetime has past some considerable time ago.

I am sure that if the WD40 company felt safe with recommending its use on potentiometers they would have included that in their promotional literature. But when they state that it is useful on “larger electric motors, armatures, relays, electric panels, and generators” I feel a little unsure about committing it to sensitive electronic purposes other than those that are stated.

There are plenty of good products out there on the market targeted at applications like that in this discussion. Why not use them?

Greg


Eric wrote:

“Greg I have to disagree with you on this one…..”


 

Eric and Greg,

The recommendation for WD-40 comes directly from the 475 Oscilloscope Service Manual, page 4-2 under Maintenance, Cleaning, Switch Contacts, the exact passage reads "There are three recommended switch lubricants. They are Silicone Versilube (General Electric Co.), Rykon R (Standard Oil), and WD-40 (Rocket Chemical Co.)." So, while Tektronix DOES specifically recommend WD-40, it is not recommended for this use. The manual specifically says of the potentiometers in the unit "most of the potentiometers used in the 475 are permanently sealed and generally do not require periodic lubrication." Of course the period that they were considering was presumably much shorter than 50 years.

I've ordered a set of syringes and industrial needles to try either forcing some lubricant down the shaft, or into a the partially opened back end of the modular pots. I would like to order some DeoxIT to use in place of WD-40, but the range of options, and CAIG's claims for the product, give me pause.

I'm not too worried about using WD-40 on the unit in general, and I'm not terribly concerned with preserving these specific three pots, as there appear to be readily available replacement units at reasonable prices (I am going to order a full set of replacements for these three pots under any circumstance. The channel #1 vertical position pot can be easily replaced without even removing the vertical input board from the unit, and that is the one that is giving me the most trouble. The channel #2 vertical position pot is not as troublesome, and I don't use the beam intensity adjustment, which is the one with most serious problems, nearly as often as I do the vertical position adjustments).


 

You should be aware that the WD-40 of 50 years ago is not the same stuff you get these days - I believe for example that it used to contain "duck oil" and that the formulation has changed at least twice since then.

Personally I wouldn't let it near a potentiometer.

David


Colin Herbert
 

There has been (and I suspect always will be) much discussion on the pros and cons in the use of WD-40. The current opinion generally is not to use it anywhere in an electronic device. There has been some mention of two differing products, WD-40 and a contact-cleaner, by the same company. It is generally understood that the common "WD-40" that you can buy from a hardware store contains a solvent which evaporates and a light oil which does not. If you want a light oil on your contacts an pot tracks, go ahead, but I wouldn't.

I don't have a Manual for the 475, nor do I have a 475, but I do have two 475As and a paper manual. In the Maintenance section of that Manual and under "Lubrication", it states that switches, potentiometers and the fan motor are permanently sealed and "generally do not require periodic lubrication". It does not mention _any_ recommended lubricants that I can see. We are all aware, I think, that the cam-operated switches can be carefully cleaned with IPA and this is indeed mentioned under "Preventive Maintenance". I appreciate that this information is a little paradoxical, but there it is. If you must attempt to clean the interiors of pots and switches, use an accredited contact cleaner, not the bog-standard WD-40.

Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jeff Dutky
Sent: 07 November 2020 10:36
To: TekScopes@groups.io
Subject: Re: [TekScopes] Clean and Lubricate Pots in Tek 475

Eric and Greg,

The recommendation for WD-40 comes directly from the 475 Oscilloscope Service Manual, page 4-2 under Maintenance, Cleaning, Switch Contacts, the exact passage reads "There are three recommended switch lubricants. They are Silicone Versilube (General Electric Co.), Rykon R (Standard Oil), and WD-40 (Rocket Chemical Co.)." So, while Tektronix DOES specifically recommend WD-40, it is not recommended for this use. The manual specifically says of the potentiometers in the unit "most of the potentiometers used in the 475 are permanently sealed and generally do not require periodic lubrication." Of course the period that they were considering was presumably much shorter than 50 years.

I've ordered a set of syringes and industrial needles to try either forcing some lubricant down the shaft, or into a the partially opened back end of the modular pots. I would like to order some DeoxIT to use in place of WD-40, but the range of options, and CAIG's claims for the product, give me pause.

I'm not too worried about using WD-40 on the unit in general, and I'm not terribly concerned with preserving these specific three pots, as there appear to be readily available replacement units at reasonable prices (I am going to order a full set of replacements for these three pots under any circumstance. The channel #1 vertical position pot can be easily replaced without even removing the vertical input board from the unit, and that is the one that is giving me the most trouble. The channel #2 vertical position pot is not as troublesome, and I don't use the beam intensity adjustment, which is the one with most serious problems, nearly as often as I do the vertical position adjustments).


Tom Phillips
 

I was able to free up a frozen intensity pot in my 465B. The 465B intensity pot is located near the rear of the interface circuit board. A long thin epoxy extension shaft connects the pot shaft to the front panel control knob. The pot shaft was so stiff that the long shaft just flexed rotationally when I turned the front panel knob as the pot refused to move. After removing the case, I set the scope vertically on the rear feet and removed the high voltage shield to access the intensity pot. I put a couple of drops of Deoxit D5 on the metal pot shaft and left it to soak. Over a day’s time I periodically added another drop of D5 when the previous drop had evaporated/penetrated down the shaft. The long epoxy shaft continued to flex and the pot shaft didn’t budge. I then used pliers applied to the metal coupling at the pot shaft to gently get rotation started. Once the pot shaft started to move things improved quickly over the next few hours because, I believe, the D5 could now better penetrate down the pot shaft.

This process took a day but it didn’t require much of my hands-on time. Eventually, I’d still like to disassemble the pot for complete internal cleaning because the intensity adjustment is a little jumpy. However, the process I described solved the main problem of a totally unusable intensity control.

Tom


 

Jeff:
Don't be mislead slightly by the removal of the 465 vertical preamp board in the eevblog tear down. The 475 vertical board differs in that the attenuator switches and BNC front panel connectors do NOT come out with the vertical board. The vertical board is separated from the attenuators by unsoldering the connection between the attenuators and the vertical board. There is a difference in what components are involved here depending upon S/N. This makes the removal a little easier than in the 465. Follow the instructions in the manual section on Vertical Preamp Circuit Board Removal. Make sure you have the correct manual for your S/N. Both of mine are S/N 250000 and up. Also be careful when removing the Delay Line connection to the vertical board as there is a solder connection here. I guess I should have photographed and documented my removal of the vertical preamp board in the 475. My bad! Some day Real Soon Now.
I have always used the Caig Laboratories line of contact cleaners and contact restorers. Cramolin and then the Deoxid line of contact cleaners. I have used the WD40 Cleaner for some applications. The WD40 brand seems to have a line of different products now. I have seen one other reference to using the original WD40, used for loosening corroded bolts, for contact cleaning/restoring. This was in a GR 1432 instruction manual dated 1956. I was surprised to see this and didn't understand exactly why. But I guess GR had some reasons for doing this. I don't think that TEK intended for WD40 to be used on the pots, nor did they expect the pots to need cleaning. But 50 years does take it toll. I am not as good 50 years later either at the ripe old age of 80.
Bill