Joel Posted July 31, 2015 Share Posted July 31, 2015 Hi guys, a couple of months ago I posted a topic (that's since been deleted) about my Cartron (Carmate) Digital Tachometer not reading revs correctly, the majority of responses was to first clean up the crappy DIY soldering that was present on the circuit board, it has since been tidied up (original solder joints have been kept) but the problem still persists and now I have a small clip showing the problem. https://instagram.com/p/5BdgH2FGD9/ In the video it shows the car being revved and held at 2000rpm the tacho reads 1600 but in brief instances flickers to 2000, then the engine is revved to 3000rpm 3-4 times and most of the time the tacho reads 400-800rpm as the car is revving up and when it is losing revs the reading will jump up and read correctly as the revs fall. Anything over 3000rpm will either flicker excessively or more commonly just won't read at all. So with the description out of the way does anyone have any idea what the issue could be? I have uploaded images of the front and rear of the circuit board in the link below http://imgur.com/a/ksNBi Sorry for the excessive use of 'rev' and 'revving' by the way haha Quote Link to comment Share on other sites More sharing options...
Bangbug Posted July 31, 2015 Share Posted July 31, 2015 Okay. Next step.Check the input signal before fucking about any more with fixes.Which means an oscilloscope (in my world of AWESOME) or if you have another tacho hook it up (in your world of POOR) and see how that goes. Ok so I'm lying, my world of CHEAP DIGITAL OSCILLOSCOPE. Since your thread disappeared how does this compare to your original problem? I see the problem still persists, but is it in the same way? Did you do a check of your capacitors and resistors etc? (multimeter). Nice pictures and video BTW. Quote Link to comment Share on other sites More sharing options...
Joel Posted July 31, 2015 Author Share Posted July 31, 2015 Thanks! I'll have a multimeter tonight to test out the capacitors and resistors. Cleaning up the ugly soldering hasn't helped at all and the issues are identical. I should note that when I had it hooked up and used for a few days there would be extended periods where the tach would cut out and not read anything at all and then at random times it would start reading again, albeit incorrectly. Quote Link to comment Share on other sites More sharing options...
Bangbug Posted July 31, 2015 Share Posted July 31, 2015 What's the vehicle/ignition? If it's a 0-12v signal you're welcome to give my oscilloscope a crack. I'm a wee way off needing it. Quote Link to comment Share on other sites More sharing options...
Bangbug Posted July 31, 2015 Share Posted July 31, 2015 Oh and I'd remove the caps before testing them.A proper test needs something (ESRM) else but a multimeter and visual should give you an indication. You can set it to ohm mode and see if the resistance climbs, at least that'll show you it's doing something Where are our electronic geeks at? 1 Quote Link to comment Share on other sites More sharing options...
downtrail Posted July 31, 2015 Share Posted July 31, 2015 How have you wired it into the car? Does the signal cable pass past the alternator at all? 1 Quote Link to comment Share on other sites More sharing options...
h4nd Posted August 4, 2015 Share Posted August 4, 2015 Maybe silly question, but are you sure it's on RPM, not battery test mode? Pushbutton stuck / faulty? 1 Quote Link to comment Share on other sites More sharing options...
kyteler Posted August 4, 2015 Share Posted August 4, 2015 Maybe silly question, but are you sure it's on RPM, not battery test mode? Pushbutton stuck / faulty?I would hazard a guess that this guy is on to something. 1 Quote Link to comment Share on other sites More sharing options...
Joel Posted August 5, 2015 Author Share Posted August 5, 2015 For sure. The battery check switch does change the reading and sits at 12v or something from memory whilst running Quote Link to comment Share on other sites More sharing options...
kempy Posted August 16, 2015 Share Posted August 16, 2015 Haven't seen or used one of those for years! can you explain what you are using for a signal and how its hooked up? To me, this looks like a dry joint for a starter, I think that is connecting to the wire link on the other side? try soldering that up better but be careful not to cook the diode with excess heat. If you're close to One Tree Hill you could always drop by and I can stick it on the Sig Gen and check what's happening + deal to the dry joint. 2 Quote Link to comment Share on other sites More sharing options...
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