Abby’s Guide > Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) > Discussions > Cheap Tachometer Hour Meter 2-4 Stroke Small Engine Spark Purchase from eBay
Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions |
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relics

Joined: Jan 15, 2011
Points: 41
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Re: Cheap Tachometer Hour Meter 2-4 Stroke Small Engine Spark Purchase from eBay
Reply #22 Mar 6, 2011 7:56 am |
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Thats great Dave now we know the ground is needed to make the tach work correctly.Did it take you long to update it with the ground wire? It also can be seen the batterys can be replaced with a little effort of removeing glue.Although i would not be surprised if there is some type of set up procedure if battery power is lost.? 
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trouts2
   
Location: Marlboro MA
Joined: Dec 7, 2007
Points: 1328
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Re: Cheap Tachometer Hour Meter 2-4 Stroke Small Engine Spark Purchase from eBay
Reply #23 Mar 6, 2011 9:19 am |
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  It will probably reset by itself with a bat install. There "reset" printed on the board so worse case those pads could be messed with. It would be nice to have a schematic. The two big chips are a 7400 series which is a simple D flip flop and probably takes the S1 and S2 inputs. The other is an 8 bit risc chip. The data sheet for it is online. It should have a reset pin which usually is pulled to ground for a reset.   The back cover comes off easily and the soldering is simple with a pencil tip soldering iron. I put a short wire on for ground and will put a perminant wire on machines so the meter can be removed easily.  The case is not brittle so easy to drill without cracking or breaking the case. The back cover also popped off easily with a knife.   Mine was advertised as "replaceable battery" and also listed as potted. It's not potted and there's no batter holder or compartment as I expected. There's probably a lot of ticked off people who bought the single lead version.   On a closer look your board and my board are very different.
This message was modified Mar 6, 2011 by trouts2
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trouts2
   
Location: Marlboro MA
Joined: Dec 7, 2007
Points: 1328
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Re: Cheap Tachometer Hour Meter 2-4 Stroke Small Engine Spark Purchase from eBay
Reply #25 Mar 6, 2011 12:24 pm |
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On the single wire units are a single "wire", no shield. I did try miniature coax starting a few inches outside the case which did not help.  It would have been better to run the coax shield as the ground inside the meter and tie the other end to the engine but I did not want to solder the shield in such a tight spot inside the meter. RF can be very weird.  It might be useful to try an R plug. It's possibly it might have cured the meter
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friiy
   
Location: Las Vegas, The Desert
Joined: Apr 11, 2008
Points: 600
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Re: Cheap Tachometer Hour Meter 2-4 Stroke Small Engine Spark Purchase from eBay
Reply #28 Feb 6, 2012 6:55 pm |
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If I remember right, the reset on the board is for awiring of a switch to reset the "hobbs" or hour meter... On some units there is a button built on the case, to reset for maintenance or serviceing needs.. I had the "Tiny-Tach" made unit for 12 or so years before the battery took a dump, never gave me a lick of problems...  If you are doing repairs or maintenance/ tune work, there is a nice unit made that is total inductive with no wires... It has a fast processor and is good to 5 rpm change in speed.. I can't remember the name (sorry)... but you had to hold it within 1 foot of the plug wire,  it was great of setting the high speed chain saws with the spark plug buried under some air induction cover.. Friiy
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