stuck odometer, type 44, infamous gear is intact - Update

[syljay at optonline.net]

Hey Konstantine !!!From: kbogach <kbogach at comcast.net>Subject: Re: stuck odometer, type 44, infamous gear is intact - UpdateYesterday night I finally turned on generator and oscillograph I bought.  They worked.  I connected generator to the pin where signal from rpm sensor come,  +12V from spare battery,   set ~200Hz which is ~130M/h.   It worked exactly like on the car - speedo works but odometer is intermittent.  It came to stop and resumed when I shook the unit a little, or tapped on the PCB.   **** Classic signs of an intermittent connection. Oftentimes, spraying with electronic freeze spray will make it work. The affected parts contract from the cold, and make electrical contact.Disconnected PCB with motor from the odometer - free motor works same intermittent.   When it did not work the signal from pin 2 and 12, which are motor driving signals,  changed its form from nothing to very short, low amplitude (~3-5V) pulses. ****Signal will get distorted and attenuated when electrical contact is lost. The small gap in the poor contact acts as a resistor/capacitor so some part of the signal gets through - but attenuated and distorted.  I also noticed that chip was most sensitive  spot  for tapping.   **** If you had looked with a strong magnifying lens or microscope, you would have found a very fine crack surrounding the base of one of the leads of the IC chip. You cannot see the crack without a lot of magnification.Having no experience with electronics I had no clue what wrong could be with chip.  I decided to re-solder everything on the PCB before I starting to look for the chip replacement.   After re-soldering I can not get this thing to stop.  I have a suspicion that I fixed it.  **** You done did fix it!  Resoldering is the standard fix procedure for such intermittent circuits.I probably will  replace the 15 tooth gear anyway. **** Yah, I hear this gear just fails from old age. Plastic gets brittle and falls apart.**** You have found out how powerful a tool an oscilloscope is in electronic troubleshooting. So, when can I borrow it?Sylvester in NJ