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    #1

    Electronic Tach

    KZ and Dink think my tach problem may be different than there's, so I'm going to re-post this.

    My tach wouldn't go above 5K. So I did the capacitor swap. Now it will get just about to 6K. When I really get on it sometimes it bounces upto 7k, then drops back down and acts eratically. Usually though, it just won't get above 5500 to 6k.

    Which wires do I need to check and how can I check the signal? I don't want to run the RPM's up with no load on it and I don't have access to a signal generator or anything like that?

    Any help is appreciated.

    Oh, and I cleaned the connectors before and didn't help.

    Dave
    Tags: None
    #2
    Didn't se this post earlier

    I put an answer in the tips & tricks post

    Comment

      #3
      I don't know about you but I'm going to just replace the whole assembly since mine has a cracked glass anyway.
      Just swap out the whole malfunctioning broken crud in one shot.

      :?
      Dm of md

      Comment

        #4
        Actually I replaced the stock instrumenation cluster this winter.....

        Comment

          #5
          Originally posted by kz
          Actually I replaced the stock instrumenation cluster this winter.....


          OMG that's beautiful!!! How'd you do it???!!!
          And with what parts!?

          8O 8O
          Dm of mD

          Comment

            #6
            Maby a better picture


            The speedo, clock and distance is a Sigma BC 800 C, http://www.sigmasport.de/index_d.html

            The tacho is a SPC-S120-W from SPA-sesign http://www.spa-uk.co.uk/design/tachometers.htm

            The oil-temp gauge is a Biltema 32-204 http://www.biltema.se/index.asp

            The indicator lights are colored LED:s, one green, one blue, two orange and two red, witch a "drilled" in place on the stock plastic cover.

            of course some rewiring, monitoring unit removed as described in Tips & Tricks, thanks JD

            Disconnected the monitoring of bulbs, gear-position display and automatic turn-signal canceling.

            Comment

              #7
              That is one nice looking bike. Great job.

              Can anyone tell me how to check the voltages to the tach. And also, do you HAVE to have a scope to check the signal from the coils?
              In addition, which wires are which?
              It's strange that the signal works fine upto about 5 or 6k, then goes to heck. Maybe it's the TYPE of capacitor? Is there a resistor type filter I can put on the wire to filter the noise?

              Thanks

              Dave

              Comment

                #8
                Originally posted by dmplatt
                That is one nice looking bike. Great job.

                Can anyone tell me how to check the voltages to the tach. And also, do you HAVE to have a scope to check the signal from the coils?
                In addition, which wires are which?
                It's strange that the signal works fine upto about 5 or 6k, then goes to heck. Maybe it's the TYPE of capacitor? Is there a resistor type filter I can put on the wire to filter the noise?

                Thanks

                Dave
                Hi Dave,

                Thanks.

                I understand that you are trying to fix this, because Suzuki-tachos doesn't come cheep.8O buying a used one makes now sense either because they have often the same problem.....

                If you want to check electrical signals you must have SOMETHING to measure with, it doesn't absolutely have to be an oscilloscope.

                You could have borrowed mine, but it's a far way to Tampa..... :roll:

                One way is to connect another tacho (an instrument with tacho-function or just another tacho) that you know is working and see if it works on your bike.

                If the bike is running as it should, the signal itself is probably OK down at the ignition coil, and otherwise the bike wouldn't run. The problem with the signal could more likely be that it is distored by something on the way up to the tacho.

                The tacho has a 12V supply, you can measure the voltage with a multimeter, connect it as close to the tachoboard as possible. Fasten the multimeter on the bike, take it for a spin, so you don't have to rev it up on the driveway and take the readings.

                I don't have a wiring diagram for the 750, but the signal wire is connected to one of the coils.

                You could also build your own new tachoboard if you know that the tachometer itself is OK.

                There is the possibility that the tachometer itself has a bad connection or that the instrument coil is damaged somehow, and the vibrations are causing the bouncing...?

                i.e.

                http://cache.national.com/ds/LM/LM2907.pdf Look at page 10

                the chip is about $3 and mayby you can use the old circuitboard?

                or

                as I wrote before, you can change parts by chance, the tacho board has not much parts, a couple of resistors, two electrolyte capacitors, two thantal capacitors, one diode and a special IC marked ND SM014.

                Check the board for cracks as well.

                I could not found the special IC anywhere and it probably contains some OP-Amplifiers, it could be that this IC was destroyed on my first tacho.

                It should be possible to mount an extra filter on the tacho input, but I don't know where to get them, check with your local electronic dealer.

                I wish you Good Luck, I know this can be very tiring and frustreting to find what is wrong, remember the days two years ago, but as the tacho finally worked it was woth it!

                Comment

                  #9
                  I think i have a scope that goes to 15mhz. Its an old heath.

                  Comment

                    #10
                    Well I might have the line on a used tach from someone here at GSr. The local scrap yard wanted $75 and I pull it. No assurance that it worked either.

                    Maybe I'll go the used route and try a different one. Between the 2 I should be able to get something working.

                    Thanks for the help. It'll be a while, so I'll repost when I find something out.

                    Dave

                    Comment

                      #11
                      Make sure you put the caps in correctly?? Regular caps should work fine . I have since found a supplier for the oem type Tantalum caps if anyone needs them .47/ 4.7 35v

                      Comment

                        #12
                        Originally posted by SqDancerLynn1
                        Make sure you put the caps in correctly?? Regular caps should work fine . I have since found a supplier for the oem type Tantalum caps if anyone needs them .47/ 4.7 35v
                        Which Caps are Tantalum?

                        My Caps had slightly different marking on (what I assume to be the negative). But I would think if I got the polarity wrong then it wouldn't work at all?

                        Maybe I need to change the other Caps as well?
                        It's a real pain to get this thing out, maybe I'll just replace every component on it, except the IC. What do you guys think?

                        SqDancerLynn1, Did you win it?

                        Dave

                        Comment

                          #13
                          Nope I didn't win the bike, I have three bikes & I really didn't need it.
                          I Got out bid It sold for $53

                          Comment

                            #14
                            Originally posted by SqDancerLynn1
                            Nope I didn't win the bike, I have three bikes & I really didn't need it.
                            I Got out bid It sold for $53
                            This is probably the ONLY time in my life that I wished I lived in California.

                            No offense to anyone in Cal.

                            Dave

                            Comment

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