[Heath] Information on 7492N (heath 443-34) binary counter please?

[Robert Groh]

I don't disagree about the possibility that the Heathkit documentation is 
wrong!  I have found that there are some pretty blatant errors (although 
relatively few) in the manuals. Your original email asked whether the 7492A 
version was different than the 7492 - I said that the two versions of 7492 are 
very, very likely the same.  I am sticking to that at this time.

Now if you were asking whether the 7490 and 7492 versions are the same - my 
answer would have been - heck, no. Different animals. 


I would be delighted to check this out in more detail if you can clarify your 
intent. I do know that there are ways you can force a reset on a partial count, 
reset to some state not equal to zero, etc.  I have, at this time, forgotten all 
the details on this stuff (after all it has been over 20 years!).  But I welcome 
the chance to get my 'little grey cells going again'.  So go ahead and feed me 
more particulars and specifics. Specifically:

1.  Which ICs are we talking about
2.  Schematics of the actual circuits or portions of the circuits (you can 
usually grab a hunk out of a pdf file, insert that hunk into a Microsoft (or 
other) document and then send that.

I look forward to the challenge!

73
Bob, WA2CKY





________________________________
From: Dean Naib <dsnaib at gmail.com>
To: Robert Groh <rgroh at swbell.net>; Heathkit <heath at puck.nether.net>
Sent: Thu, February 24, 2011 1:40:25 PM
Subject: RE: [Heath] Information on 7492N (heath 443-34) binary counter please?


Hi Bob,
 
I agree with you but the Heathkit manual text and the waveforms on the 
schematics clearly show it is resetting to 5 rather than zero.  Comparing the 
74LS90 to the 7492N   (the freq meter uses both), the 90 has two sets of reset 
pins while the 7492N has only a single set which would seem to indicate that it 
only supports a zero reset.  I am going to assume the heathkit documentation is 
wrong.
 
Thanks,
 
Dean, K4DSN
 
 
From:Robert Groh [mailto:rgroh at swbell.net] 
Sent: Tuesday, February 22, 2011 4:01 PM
To: Dean Naib; Heathkit
Subject: Re: [Heath] Information on 7492N (heath 443-34) binary counter please?
 
Dean,

I think that it is extremely unlikely (based on 40+ years in electronics design 
and even involving the SN7400 family) that the A version of the SN7492N is any 
different in any significant way than the A version. Do a Google (or Bing or 
whatever) search for sn7492n and you will find many, many links to the 
datasheets.

73
Bob, WA2CKY
 

________________________________

From:Dean Naib <dsnaib at gmail.com>
To: heath at puck.nether.net
Sent: Mon, February 21, 2011 6:59:20 PM
Subject: [Heath] Information on 7492N (heath 443-34) binary counter please?



Does anyone have a datasheet for the 7492N?  
 
I have found sheets for the 7492AN but the heathkit manual for the IM-2410 freq 
counter explains that the reset signal should be resetting  the count to 5 but 
the 7492AN datasheet says the reset sets it to 0.  My  counter has a DM7492AN 
installed which I don’t think is correct.  The problem I’m having is that I am 
not able to read any frequency below around 50 khz regardless of amplitude.  The 
clock pulse coming out of the DM7492AN doesn’t match the wave form on the 
schematics, there should be a notch toward the end of the clock pulse caused by 
the reset of 5 but instead I’m seeing a full 0 reset and no notch being taken 
out of the clock pulse.  I would like to know if the 7492N does have a different 
reset then the AN version but I can’t find a datasheet for it.  Does anyone know 
?
 
Thanks,
 
Dean Naib
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