[R-390] Sticking Carrier Meter

[Ken Harpur]

Thank you Charles, the points you raise hadn't even occured to me. I just assumed it was the bearing screw because I had read on an R-390A site that the owner had relaxed that screw and it worked for him.
After reading your comments I consulted google again to try and get some more ideas and came across a link that suggested one of the most common causes of sticky meters is as you say in your first point...

"The cause of the sticking is much more likely to be (i) crap in the magnet assembly rubbing on the armature"

I'll have a good look at it when it is open and make sure I have identified at least a possible cause before I touch anything...and given what you say about the bearings I think I'll leave that screw alone.

Once again thanks for the advice I will use it all to try to fix it...hopefully I will be able to come back to the list with good news!!

Kind regards
Ken



On 23/03/2012, at 5:41 PM, Charles P. Steinmetz wrote:

> Ken wrote:
> 
>> I'll get onto it this weekend and let everyone know how it went...
> 
> One thing before you dive in:  I believe you mentioned loosening the 
> movement screw as a potential fix.  If anything, the meter bearings 
> should have more clearance now than they did when the meter was new, 
> due to wear.  So it is probably not advisable to loosen the bearing 
> screw, unless you can clearly see that some physical damage has moved 
> one bearing closer to the other (almost certainly not the case).  The 
> cause of the sticking is much more likely to be (i) crap in the 
> magnet assembly rubbing on the armature, (ii) something else rubbing 
> (needle on face, spring on wire, etc.), or (iii) dirt/grime in the 
> bearings.  Loosening the bearings won't help the first two, and even 
> if it helps the third, it is the wrong thing to do and the "fix" 
> won't last long.  Figure out what is the matter, and fix that.  If 
> it's dirty bearings, use a *non-magnetic* small pointy thing (e.g., 
> plastic toothpick) to put solvent in each bearing, then exercise the 
> meter, then put in more solvent, etc., etc.  When it is free, use the 
> pointy thing to put the smallest drop of very light oil on each 
> bearing.  (Light mineral oil like sewing machine oil or the oil that 
> comes with electric shavers is good.  Real watch oil is, too.  Sperm 
> oil, if you have any (which is probably what it had from the 
> factory).  Jojoba oil works fine if you can't find any of the 
> others.  Do NOT use 3-in-1 oil or similar oxidizing oils.
> 
> General axiom of troubleshooting and repair, # 17:  Don't fix the wrong thing.
> 
> Best regards,
> 
> Charles
> 
> 
> 
> 
> 
> 
> 
> 
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