SB-300 LMO Warble

[John Q. Doe]

Bill

If you are lucky your rig will have the LMO with metal foil tape covering access holes in the top or sides of the LMO. Those access holes will allow you to access each end of the variable cap without having to pull the LMO out and disassembling the beast.

If you can access the end bearings then you can lube the cap and stop the warble.

What I have done is to use a hypodermic syringe with Luer lock and a plastic tip attached to the syringe. The plastic tip has a flexible plastic tube atteched. These are available through houses that sell hybrid circuit adhesives or possibly your nearby pharmacy. (The pharmacist however may ask why you want a hypo syringe and flip out when you tell him that you are going to fill it with lithium grease. Some folks are shooting up with some strange concoctions thee days. :-)  I then remove the plunger and carefully squeeze in a small amount of white lithium grease into the barrel of the syringe. Replace the plunger.

Take a glass or jar you will not use for food or drink ever again. Fill it with water. Place the syringe assembly with plastic tip and plunger into the glass or jar and submerge it in the water. You may have to use duct tape to hold the syringe down in the water. Place the glass or jar in the microwave oven and heat for about 1 minute. Try to raise the temperature of the water to near boiling. The objective is to get the lithium grease to melt to a liquid without melting the syringe.

Once the lithium grease is melted you can carefully insert the tip of the syringe into the LMO at each bearing and relubricate the bearing. It does not take much. Perhaps less than 0.1 cc at each bearing is more than adequate.

Rotate the tuning shaft and check the radio to see if you still have a warble.

Many insist that you must clean out the old lubricant before applying new. I do not remove the old lube if the unit has been sealed. (Per Heath Tech in 1978 - The lubricant contains silver particles. It is suppose to improve the conductivity of the plate shaft to ground. I was not told why this was important but suspect someone was looking for a minor improvement in circuit Q.) In any event if the silver is critical then it remains and mixes with the lithium grease.

I inquired a few months back about sources of lubricants with silver particles and was given the name of a British firm. I tracked it on through to a domestic US distributor and obtained a quote from the distributor. A small can (1 ounce if my memory serves me correct) was about $150.00. There was a larger can that was in the $400.00 range.

Best of luck

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