<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman,new york,times,serif;font-size:12pt">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.<br><br>Now if you were asking whether the 7490 and 7492 versions are the same - my answer would have been - heck, no. Different animals. <br><br>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:<br><br>1. Which ICs are we talking about<br>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.<br><br>I look forward to the challenge!<br><br>73<br>Bob, WA2CKY<br><div><br></div><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;"><br><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;"><font face="Tahoma" size="2"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> Dean Naib <dsnaib@gmail.com><br><b><span style="font-weight: bold;">To:</span></b> Robert Groh <rgroh@swbell.net>; Heathkit <heath@puck.nether.net><br><b><span style="font-weight:
bold;">Sent:</span></b> Thu, February 24, 2011 1:40:25 PM<br><b><span style="font-weight: bold;">Subject:</span></b> RE: [Heath] Information on 7492N (heath 443-34) binary counter please?<br></font><br>
<meta http-equiv="x-dns-prefetch-control" content="off"><style><!--
_filtered {font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;}
_filtered {font-family:Tahoma;panose-1:2 11 6 4 3 5 4 4 2 4;}
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;margin-bottom:.0001pt;font-size:11.0pt;font-family:"sans-serif";}
a:link, span.MsoHyperlink
{color:blue;text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{color:purple;text-decoration:underline;}
p.MsoAcetate, li.MsoAcetate, div.MsoAcetate
{margin:0in;margin-bottom:.0001pt;font-size:8.0pt;font-family:"sans-serif";}
p.msochpdefault, li.msochpdefault, div.msochpdefault
{margin-right:0in;margin-left:0in;font-size:12.0pt;font-family:"sans-serif";}
span.emailstyle17
{font-family:"sans-serif";color:windowtext;}
span.BalloonTextChar
{font-family:"sans-serif";}
span.EmailStyle21
{font-family:"sans-serif";color:#1F497D;}
.MsoChpDefault
{font-size:10.0pt;}
_filtered {margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{}
--></style><div class="WordSection1"><p class="MsoNormal"><span style="font-family: "sans-serif"; color: rgb(31, 73, 125);">Hi Bob,</span></p><p class="MsoNormal"><span style="font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p><p class="MsoNormal"><span style="font-family: "sans-serif"; color: rgb(31, 73, 125);">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.</span></p><p class="MsoNormal"><span style="font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p><p class="MsoNormal"><span style="font-family:
"sans-serif"; color: rgb(31, 73, 125);">Thanks,</span></p><p class="MsoNormal"><span style="font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p><p class="MsoNormal"><span style="font-family: "sans-serif"; color: rgb(31, 73, 125);">Dean, K4DSN</span></p><p class="MsoNormal"><span style="font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p><p class="MsoNormal"><span style="font-family: "sans-serif"; color: rgb(31, 73, 125);"> </span></p><div><div style="border-width: 1pt medium medium; border-style: solid none none; border-color: rgb(181, 196, 223) -moz-use-text-color -moz-use-text-color; padding: 3pt 0in 0in;"><p class="MsoNormal"><b><span style="font-size: 10pt; font-family: "sans-serif";">From:</span></b><span style="font-size: 10pt; font-family: "sans-serif";"> Robert Groh [mailto:rgroh@swbell.net] <br><b>Sent:</b> Tuesday, February 22,
2011 4:01 PM<br><b>To:</b> Dean Naib; Heathkit<br><b>Subject:</b> Re: [Heath] Information on 7492N (heath 443-34) binary counter please?</span></p></div></div><p class="MsoNormal"> </p><div><div><p class="MsoNormal">Dean,<br><br>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.<br><br>73<br>Bob, WA2CKY</p></div><div><p class="MsoNormal"> </p><div><div class="MsoNormal" style="text-align: center;" align="center"><span style="font-size: 10pt; font-family: "sans-serif";"><hr width="100%" align="center" size="1"></span></div><p class="MsoNormal"><b><span style="font-size: 10pt; font-family: "sans-serif";">From:</span></b><span style="font-size: 10pt;
font-family: "sans-serif";"> Dean Naib <dsnaib@gmail.com><br><b>To:</b> heath@puck.nether.net<br><b>Sent:</b> Mon, February 21, 2011 6:59:20 PM<br><b>Subject:</b> [Heath] Information on 7492N (heath 443-34) binary counter please?<br></span><br><br><span style="font-size: 12pt; font-family: "serif";"></span></p><div><p class="MsoNormal">Does anyone have a datasheet for the 7492N? </p><p class="MsoNormal"> </p><p class="MsoNormal">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 ?</p><p class="MsoNormal"> </p><p class="MsoNormal">Thanks,</p><p class="MsoNormal"> </p><p class="MsoNormal">Dean Naib</p><p class="MsoNormal"> </p></div></div></div></div></div><meta http-equiv="x-dns-prefetch-control" content="on"></div></div>
</div></body></html>