Re: Clean and Lubricate Pots in Tek 475


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).

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