Lubrication

[Silicon]

Is there a consensus on the best lubricant to use on different parts of a radio chassis?

I want to lubricate:-

(a) the variable capacitor (‘tuning vanes’) spindle.
(b) the ‘slider’ that holds the tuning pointer.
(c) the spindle that moves the ‘dial cord’.
(d) the spindles in the volume/tone controls.

In some situations the lubricant might creep across surfaces and contaminate the dial cord. Can that be avoided? Does it do any harm? What is the best way to clean dial cord? If a clean dial cord is slipping do you have any suggestions on how to fix it?

P.S. Does anyone lubricate valve pins to maintain good contacts (i.e. Servisol)?

[Mike Phelan]

(a) Grease, if it is the usual sort with a ball-race at one end and a single ball at the other one.
(b) Spray polish
(c) Grease, if it is just a plain bush
(d) Grease after dismantling it.

Anything with sintered bronze bearings needs a long soak in IPA or petrol, then an overnight soak in oil at about 150C - temperature not critical and your oven is a good place.

When I refer to grease, not the silicon sort, but the automotive (Castrolease LM or similar) or any other general-purpose grease.

Personally, I would replace dial cord if it was very dirty or old.

I thought that this post would generate a lot of opinion but in the absence of any other reply I will get the ball rolling and no doubt get comment about my suggestions (constructive of course).

a) Tuning Capacitor - Depends upon the construction of the capacitor and its bearings – on ones with ball bearings the stiffness is often owing to grease that has gone hard and this needs to be cleaned out and replaced. Simply washing the bearing out with WD40 or similar will not do. Stiffness can also be due the corrosion particularly on types that use a brass bearing and steel spindle, here WD40 followed by a small amount of thin oil may do the job.
b) Dial Pointer slide- Cant beat rubbing it very lightly with a candle but some of the dry lubricants for car hinges etc could be useful providing you don’t use a spray and get it in the drive cord.
c) Dial cord Drive - Again WD40 to clean it and then light oil. If the spindle is held in place with a circlip it is worth dismantling it to clean it.
d) Volume/Tone Control - This is a problem because you don’t want the lubricant to creep into the pot. If it is really bad I would dismantle and clean and then put a small amount of lubricant on the bearing. Unless it is particularly stiff or seized and the track is not dirty I would tend to leave it alone.

The main point is only put the lubricant where it is needed and avoid the use of sprays when the component is still in situ. Contents of spray cans can contaminate the most unlikely places and cause future problems. Also identify the problem before applying a solution e.g is it due to lack of lubrication, dirt or corrosion?

I know of no way of cleaning drive cord and if it is contaminated I would replace it. Roughing up the spindle with fine emery often helps because the surface gets polished over time.
(I have recently bought a small ultrasonic cleaner that is proving to be very useful for some of the cleaning problems we encounter.)


Regards
John

[Al (astral highway)]

Originally Posted by Silicon

P.S. Does anyone lubricate valve pins to maintain good contacts (i.e. Servisol)?

I don't think there's any reason to go this far. The valve holder is designed to apply quite a squeeze over the pins and so the trick is to make sure that the pins and socket are clean.

I use grade 0000 glass wool for the pins and an improvised 'pull through' where this is possible. Otherwise, I lightly push and pull a tiny twist drill into the socket, so removing any oxide from the valve holder. You don't need to apply power to the twist drill. You're basically using the sharp edges as a precision scraper.

If I were going to use a conductive lubricant, I still wouldn't miss out this stage, which is going to have more impact in its own right.

[Al (astral highway)]

Originally Posted by jmshep

I thought that this post would generate a lot of opinion

It normally would, but this may be a slightly quiet period for the forum, as people rush around doing last minute Christmas stuff. Give it a few hours.

[jjl]

I wouldn't use Servisol on valve pins and certainly not on valve sockets. It is possible for such fluids to soak into the valve socket insulation and alter its characteristics, or even make it conductive which would be bad news.

John