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Folks Of Interest Sun Tach transmitter EB series rebuild

Discussion in 'The Hokey Ass Message Board' started by 38 2 DR Sedan, May 13, 2020.

  1. john worden
    Joined: Nov 14, 2007
    Posts: 1,726

    john worden
    from iowa

    I have one at Bob's now.

  2. I got the schematic I used from a thread on this forum about 10 years should be able to find it in the archives. Use the diode in the existing circuit......use 12 volts from the ignition switch.....pretty simple. I have also seen similar schematics on the internet. I got the diodes from a guy in Oregon.....will need to find the receipt in my shop...they were dirt cheap for a pack of 15. I also discussed these mods with the tech guys at the company who owned SUN Electronics back then........they pulled up the original drawings while we were on the phone.....they said it was designed so crudely (back in the day) that pretty much any of these mods would work......very forgiving design.
    Inked Monkey likes this.
  3. Well.....I found a ZENER diode schematic in my files, but am having difficulty uploading it...will try again later. It also uses a 500 ohm shunt resistor, which I forgot to mention in the previous posts.

    Another approach on these senders is to use two 1.5 volt AA batteries in place of the original 1.35 volt mercury batteries. I have several SUN tachs and use DURACELL PROCELL batteries with good success in need to make sure the innards of the box are can replace the capacitors quite easily......they are the most suspect item in the box. One downfall of the original design is that it is "hot" all the time, which can deplete the batteries quicker.....the distributor is simply a trigger.

    Remember these units were never very accurate by current standards.....they are more for bragging rights today. The ZENER diode conversion does not improve the accuracy.......only functionality. If you need accuracy, best get a solid state tachometer.....or pay the freight for a solid state conversion.
    stillrunners likes this.
  4. Beanscoot
    Joined: May 14, 2008
    Posts: 2,193


    In case anyone's interested, there is a guy in Russia selling the original type mercury batteries. He used to be on ebay but now he has his own site.
    Just search with the battery number to find him.
    I think the main customers of these batteries are the vintage camera crowd.
  5. 1934coupe
    Joined: Feb 22, 2007
    Posts: 4,681


    I don't mean to offend anyone but, why would anyone be interested in buying a mercury battery from a guy in Russia for their tach is beyond me.

    38 2 DR Sedan likes this.
  6. Beanscoot
    Joined: May 14, 2008
    Posts: 2,193


    Some tachs were designed to use the particular mercury battery, and don't work properly on anything else.
    Thus the workarounds with electronics.
  7. E-bay, from the comfort of my couch.
  8. It is really easy, just check the price of components on e-bay, follow the directions and put it together. worked the first time. if we can build motors, set up suspensions and stuff we can surely solder little wires together.:)
    Inked Monkey and stillrunners like this.

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