Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => AmpTools/Tech Tips => Topic started by: John on June 08, 2013, 01:08:32 pm
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http://www.electro-tech-online.com/custompdfs/2008/02/DC-1.pdf (http://www.electro-tech-online.com/custompdfs/2008/02/DC-1.pdf)
Found this while researching how to turn a 150 range meter into a 450. Thought it useful.
If I somehow manage to successfully do the mod on the meter, trust me I'll be here to brag about it. :laugh:
*edit* The needle doesn't swing free. I can't say it sticks exactly, but it doesn't move freely either. Any fixes that aren't too involved? It's a Simpson that I got for $5 so I wasn't expecting much, and I'm not interested in spending a lot of money to repair it.... not that big a deal.
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> needle doesn't swing free
Open it up and look. Odds are that you will foul up beyond all repair (fubar), but there's a slight chance you can dislodge an ant-turd and free it; otherwise a $5 lesson on how delicate meter movements are, cheap at the price.
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@John I'd advise, just open it up and look. Don't mess around with it unless you're sure what you're doing. The needle's movement could be elastic for other reasons as well. You can try changing the resistance parameters to find an exact match of where the needle acts more stiff. Once you start observing a positive behavior you can simply balance it according to your requirements. However, I'll advise you not to meddle if you're not sure. Study the schematics first and start when you're completely sure about what you're doing.
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Sorry I never followed up, this was just a panel meter, not a vom or anything like that.
Never did figure out why the needle was sticky. By taking it apart I was able to play with different resistors and see the difference that made, so just a nice relaxing way to spend an hour or so. Then I dismantled it and use the magnet part of it to magnetize screwdrivers. :laugh: As PRR said, it was a $5 lesson. And Beny, thanks for taking the time to reply also!
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In general, when shipping (or storing) an old-style D'Arsonval meter, you want to short the terminals which has the effect of damping the meter movement.