[Collins] Sticking KWM-2 meter

[Gerald Johnson]

Simple things first. Make sure the glass is not loose and leaning back against the pointer. Then be sure the glass hasn't a static charge. Spray it with an antistatic spray or wash it with a strong dishwash solution and don't rinse. Don't polish on the glass, that is how the glass got the static charge.

Failing those its more delicate to take the meter out of the case, probably after taking the meter from the radio. Three screws through the side of the barrel at the back. Slide the meter out (on a really calm nerve day, kids in school, spouse shopping, clean bench). Move the pointer with your breath watching to see its not smashed against the scale. Tighten the scale mounting screws to be sure the scale isn't leaning. If the pointer is dragging on a solidly mounted scale, use two toothpicks to bent it away gently. Hold one in front of the pointer where the right angle bend is to force the tend to be in the upright part of the pointer, then lift part way out on the pointer with the others. THIS IS A DELICATE OPERATION and too much bend can make the pointer drag on the glass, or break the pointer off. Check for free pointer motion by blowing gently on the pointer.

With the meter out of the case, you can push the glass and glass retaining ring torward the front of the meter to hold the class more securely if it was loose.

It its not static cling or a dragging pointer, its probably much serious. Could be tangled hair springs which should be a continuous evenly spaced spiral, but they can be tangled by shock. Sometimes they can be untangled with the toothpick or a pair of toothpicks. The hair springs are an order of magnitude more delicate than the pointer. Sometimes the hair spring has been bent at the outer anchor to lead to the tangle, sometimes it can be straightened with the two toothpicks, sometimes it breaks. That's generally terminal, few in the world have the delicate touch and patience to replace hair springs.

It could be magnetic debris on the pole pieces catching the coil. Sometimes these can be removed with narrow strips of Scotch or masking tape gently slid into the air gap and snaring the debris with the stickum. Air probably won't move the steel chips.

If its bearings, its probably terminal. Too much shock can bend or crack the spindles attached to the coil and make it run off center and drag. I don't know of anyone alive who can successfully fix that on a meter of that size. Not to say that they might exist, but I just haven't found anyone willing to get that intimate with a meter movement in nigh on 40 years.

When reassembling the meter, be sure that the zero adjust peg is in the slot on the zero adjusting mechanism and that the glass has had an antistatic treatment inside. The install the three screws and remount and rewire the meter.

When loosening and tightening the nuts on the posts, its a great idea to have a thin wrench on the nut against the back of the meter so the posts don't work loose from that process.

Other than the static problem from too much meter glass polishing, the other problems come from the glass being pushed in against the pointer or from extreme shock. Meters can't take the impact that a LED flashlight takes or that building stones dumped from a truck take. Meters get bent and hairsprings tangled from big shocks.

73, Jerry, K0CQ, Technical Advisor to the CRA

Copyright retained by Dr. Gerald N. Johnson.
---------- Original Message ----------------------------------
From: "Bob Rinaldi" <w1cny@comcast.net>
Date:  Sat, 1 May 2004 17:12:29 -0400

>Any magic for curing a sticking a KWM-2 meter !  :)
>Thanks,
>Bob
>W1CNY
>..
>