Re: Tek 494AP VR board mystery


Jim Ford
 

Or the famous Cadence vs. Avanti EDA code lawsuit.  Very hard for Avanti to explain the exact same misspellings in the comments!  Sure you didn't steal Cadence's IP, Avanti!  Case closed.          Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: John Miles <john@miles.io> Date: 7/15/21 11:42 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Tek 494AP VR board mystery > I'm almost 100% sure it is just a snafu that happens all the time and was> quite widespread back then when CAD didn't exist yet but leave 0.00001%> doubt of missing something.Agreed, that is very weird.  Same with those resistors... usually you try tominimize the number of BOM line items by consolidating resistors, but theyseem to have done the opposite here.  The LC BPF at the output of the A69 post-VR amp is also funky.  On theschematic, the inductors are 0.652 uH, 0.568 uH, 0.652 uH, 0.94 uH, 1.047uH, 1.047 uH, and 0.94 uH, but in the parts list they are morereasonable-looking values.  Meanwhile, the capacitors are bog-standard 220pF and 470 pF parts.The filter could be explained by the engineering department getting a littletoo carried away with their new computer, or maybe they just measured theparts they used and transcribed the values to the BOM without rounding.Likely true for the "1.047 uH" toroids, but it doesn't explain the others,and nothing explains CR3068 as far as I can tell.  I wonder if it's an IPprotection feature.  If Hickok or Lavoie or somebody like that were to clonethe instrument, things would get awkward if they had to explain what thatdiode was for in court.   Similar to the practice of adding fictitious townsto a map to guard against commercial copying.-- john, KE5FX

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