[Heath] IM-2420 Freq Counter problem

[Ronald Carlson]

Alex, 

The first place I'd check is the circuitry as described in Section #16 on pg 78 of the manual.  Check the output of the decade counters that feed the latch decoder driver.  From a display of 106.9400 MHz this might be the 3rd LSB for the 6th decimal digit (V3 perhaps?).  Reset U22, U28 and U29 first.  If that doesn't do it, check with a logic probed / scope on U28 and U29 input pins from U29, the third bit (2^2) seems disconnected.  Or just carefully resolder all the pins on U22 and U28, maybe U29 for good measure too.  Let us know!


If you need a schematic, illustration set, manual let me know.
 
Regards, Ron


>________________________________
> From: Alexander N. Gerli <ac1wye at gmail.com>
>To: "heath at puck.nether.net" <heath at puck.nether.net>; heathkit at mailman.qth.net 
>Sent: Thursday, September 25, 2014 4:41 PM
>Subject: [Heath] IM-2420 Freq Counter problem
> 
>
>
>Hi, gang!
>
>
>I'm trying to figure out something. My counter does count, but one digit's way off - the x10MHz. For instance, if I key up my HT nearby on 146.34/94, the counter displays "106.3400" Off by 40MHz. Now, I can't find any such anomaly covered in the "ICOD" section of the Manual (naturally...). I'm figuring that I need to recalibrate the 10mHz Oscillator inside its styrofoam oven. I have another portable counter I can use and it is right on. But if it were off by that much, how come the suffix reading of .340mHz comes out on the nose? Anybody have any suggestions? Maybe a divider chip could be off, but I have NO idea which one. I guess I could reseat all the chips  in their sockets?
>
>
>​73,​
>
>​Sandy AC1Y​
>
>Alexander N. Gerli, Sr.
>548 Allred Mill Road
>Mount Airy, NC 27030-2202
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