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 Post subject: Meter bounce.
PostPosted: Apr Mon 14, 2003 4:48 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1729
Location: Eagan, Minnesota, USA
I just replaced the paper and electrolytic capacitors in my Hickok 209-A VTVM, including the one accross the meter.<P>The meter action is not very stabil and smooth. It will jump around before settling at the point is should read. On the ohms setting, it will easily peg the outer ends of the meter if you are taking a reading near there. I short, this meter really jumps above and below a reading before it settles down and provides you with the reading.<P>I also tested the tubes, and they are good.<P>I am assuming that a meter like this should provide a smooth, stable, controlled reading.<P>Any ideas on this???<P>Frank<P><P>------------------<BR>


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 Post subject: Meter bounce.
PostPosted: Apr Mon 14, 2003 7:23 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12279
Location: Mpls, Minnesota
Frank<BR>Did you use a 15mfd on the meter and is the polarity correct? You can go higher with the value to settle the meter down to where you want it, on some meters I have gone as high as 1000 mfd to get a real smooth action. You only need a 25 volt electrolytic so it should be easy to find one you like.<P>Dave<P>------------------<BR>


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 Post subject: Meter bounce.
PostPosted: Apr Mon 14, 2003 3:32 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1729
Location: Eagan, Minnesota, USA
I had a 22 mfd @ 35 volts cap, and installed it. Looking at the meter from the rear, I installed the positive side on the left terminal, and the negative on the right terminal. <P>Is this capacitor what eliminates this meter bounce? I wonder if I have a bad cap here, or maybe it's reversed? (I thought I paid attention to the old cap, but you never know...).<P>Frank<P>------------------<BR>


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 Post subject: Meter bounce.
PostPosted: Apr Mon 14, 2003 5:24 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 795
Location: Gulf Breeze, FL USA
Check the isolation cap thats in the positive input circuit. It is probably not an electrolytic, but will be a high voltage paper type (1000v +). I've seen this symptom in other VTVM's caused by the isolation cap.<BR>Your new cap may be bad.<BR>------------------<BR>


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 Post subject: Meter bounce.
PostPosted: Apr Fri 18, 2003 8:05 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1729
Location: Eagan, Minnesota, USA
I think that if I go to a much higher value cap, the meter will act more smoothly. I'm thinking of going from the 22mfd cap to a 100 or 200 mfd cap. But, if I do this, will it create any problems for me? And, why did the factory not use a larger value to begin with?<P>Please advise.<P>Frank<P>------------------<BR>


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 Post subject: Meter bounce.
PostPosted: Apr Sat 19, 2003 4:31 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 596
Location: Buckingham County, VA. (Foothills of the Blue Ridge Mtns)
I have had much experience over the years with Hickok equipment and found them to be very reliable and quality equipment. No, your meter is not supposed to bounce like that, the needle should swing smoothly to the indication point without overswing (or bounce as you suggest). The capacitor on the rear of the meter acts as a damper of sorts .. it charges and absorbs the initial surge to prevent this. The cap may be bad or installed incorrectly (polarity or bad solder joint). If you have to use a larger cap, then I would suggest that you are fixing the result of a problem and not the cause of the problem. Hickok would have designed this instrument to perform well, and the value cap that was in it should be correct. If the cap on the meter is the correct value and installed correctly, then there is probably something wrong in the detection circuit (as cathode follower suggests) that is causing this and not in the indicating circuit (meter).<P>------------------<BR>


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 Post subject: Meter bounce.
PostPosted: Apr Sat 19, 2003 6:41 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 477
Location: NC
Frank,<P>Gordo has a good point with his reply. <P>It would be a good idea to check the VTVM's tube pins and tube sockets to make sure they are clean and not making intermittent contact.<P>If wiggling the tubes in the VTVM causes erratic readings (meter movement), you may have a problem there that is easy to correct.<P>------------------<BR>Ken


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 Post subject: Meter bounce.
PostPosted: Apr Tue 22, 2003 3:39 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1729
Location: Eagan, Minnesota, USA
I'll check the tube sockets. What part of the circut are we referring to that I should re-check? I have the schematic here, and could work from it.<P>------------------<BR>


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 Post subject: Meter bounce.
PostPosted: Apr Tue 22, 2003 4:24 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 4437
Location: Connecticut. USA
Frank,<BR>What I always do to every thing that has tubes in it is to pull one tube out at a time and spray the tube sockets with contact cleaner.<BR>When doing this, put the tube in and out several times to clean the pins and socket, sometimes you have to re-spray again if you have the kind of stuff that evaporates like the CRC spray I use.<BR>I have done this to many radios and test gear and it saved a lot of headaches.<P><P>------------------<BR>Bill Benson<BR>Bill267Benson at wmconnect dot com


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