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Author Topic: eico 720 meter  (Read 969 times)
NT6R
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Posts: 6




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« on: February 05, 2013, 02:06:39 PM »

Howdy, I received an Eico 720 with a damaged meter.  I don't think the meter is repairable so am looking for a direct replacement or some kind of substitute.  Any help would be appreciated.  Gene
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N4NYY
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« Reply #1 on: February 05, 2013, 03:21:24 PM »

What is the meter measuring? mA? I cannot see by Googling the pics. If it is a current meter, that should be easy to replace.
« Last Edit: February 05, 2013, 04:02:18 PM by N4NYY » Logged
NT6R
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« Reply #2 on: February 05, 2013, 03:42:22 PM »

N4NYY, tks for the response, the meter measures grid current for the driver (nominal 3 MA)
and plate current for the 6146 (somewhere around 160 MA).    I'm sure there is a shunt resistor in there to compensate for the two ranges.  However, the EICO schematic doesn't give the measuring specs for the meter.  It's just called M1.  So, I don't know the value
of the meter.  Tks agn, any ideas? Gene
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N4NYY
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« Reply #3 on: February 05, 2013, 04:04:16 PM »

Gene,

May be a 10mA meter. These should be available everywhere and cheap. I am sure it is a shunt. I have seen to many of these on ebay or hamfests. The biggest problem you will have it matching up the hole. Might have to do some surgery.

Here are a couple on ebay, round and square: http://www.ebay.com/sch/i.html?_odkw=1ma+meter&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313&_nkw=10ma+meter&_sacat=0

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KE3WD
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« Reply #4 on: February 05, 2013, 08:00:19 PM »


A couple of insulated alligator clip leads from your DMM set to the highest mA scale first, clipped in place where the meter used to be can sort out what current the replacement meter should be rather empirically. 

Start on the highest mA scale first because that's good practice and shouldn't hurt your DMM, then gradually reduce the scale until it is around where you get good readings. 

From that you should be able to ballpark the true meter spec, or rather what it should be at fullscale reading. 


73
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NT6R
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« Reply #5 on: February 06, 2013, 12:03:45 PM »

 N4NYY and KE3WD: Tks for the info, now I have a plan and can move forward.
73's and all the best from WV.  Gene 
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