I happened to notice the other day that an analog voltmeter that I built a couple years ago was reading 10 volts. Now this alone would not have been of any concern except for the fact that the power supply was not turned on nor had it been turned on for several days. I went over and tapped the meter and it dutifully dropped back to zero. Years ago when I did service work for Radio Shack it was common to have the little analog multimeters come in for repair with stuck meter movements. I would take them apart and the usual cause would be a metal filing suspended in the magnetic field where the movement coil would normally swing. Once the filing was spotted any sharply pointed ferromagnetic tool could extract the filing by touching it with the point of the tool and pulling it out using the magnetic field. Since the meter movement of this power supply was not very expensive I expected to find a similar problem. I really like this power supply and I really didn't want to have to replace the meter so I popped the front cover off. To my delight this is what I found:
There just south east of the DH-670 was a hair like finger of white paint acting like a tiny ratchet. The needle could pass by it on the way up but on the way down it would get hung up. The picture also revealed a couple other signs of the quality of this meter. Note the rust on the screws holding the front plate and even a dust bunny clinging to the left mounting screw pulled perhaps from the sleeve of the factory assembler. Fortunately when I removed the finger of paint and the dust bunny the meter started working as good a new and since I have tolerant standards in my test equipment more than adequate for me.
John
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