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Fritzy Tachometer  Rating:  Rating
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 Posted: 08-15-2008 04:52 am
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JodyFKerr
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No readings = crappy readings.

Bsed on my understanding of the tachometer (I took one apart a while back, so colour my ingorance for me) the issue is most likely in the wiring reaching the unit, not the tachometer itself. It is, in general terms, too simple to fail. First off, clean the terminals on the back of the tach to see if you get any improvement. If not, pass a volt meter across the connectors to determine if the to tach is reading any varations. (good variations = bad tach). If not, then it's diagnostics floating back through the wiring. I can't find my diagrams right now, but it's not a clean trace IIRC.

 

Jody

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 Posted: 08-15-2008 07:37 pm
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dwalls1
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Hello Jody,

   From what I have gleaned on this thread, if the tach isn't getting a signal then the coil isn't either and the engine won't run. I will be playing with it tonight and see if I can narrow it down to a single component failure, perhaps the capacitor mentioned in earlier posts on this thread. Your dead on about this being a simple unit. The technology was about 10 years obsolete 35 years ago, which makes it about 45 years ahead of my understanding of electrical gadgets. I'll let you know how I make out. Dale

 

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 Posted: 08-23-2008 04:58 am
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dwalls1
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FWIW I've sent my tach to MOMA in Alburquerque. I've asked them to repair it as a stock unit without the capability of using it on a pointless ignition. I'll probably regret it, but hope to run the points for as long as I own the car. I can have it reworked later to work with the pointless system, but it would be more money. Oh well, what isn't.

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 Posted: 08-27-2008 04:57 am
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dwalls1
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Got the tach back in this evening and it works fine. MO-MA got it on the 21st and returned it to me on the 22nd. Wow! talk about your turn around time.

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 Posted: 11-25-2010 08:07 am
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maddog55
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Did you ever find out what kind of transistor that was?

I'm working on repairing the smith tach I've got. Everything is fine now but still need to know what the part is PNP probably but not sure.

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 Posted: 08-01-2013 05:01 am
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atgparker
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Hey, do a search on RVC tachometer and you will find a few listings for Smiths Tachometer RVI to RVC conversion boards.
Spiyda Design does pay pal and lists on eBay. There is dynoplex.org which has the bits and pieces for a DIY solution as well. I'm going to swap out the board on my Smiths RVI 1439/O3A so that the Pertronix ignition will trigger the tachometer correctly as it is RVI at the moment it doesn't work much above 5,000 RPM.

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 Posted: 08-02-2013 06:28 pm
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answerman
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I've been looking at the Spiyda Design board, just haven't gotten around to pulling the trigger on it yet. Though I'm still running the stock ignition, I'd rather hook up the tach in the RVC fashion anyway. Let us know how the conversion goes.

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 Posted: 08-22-2013 09:06 pm
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atgparker
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The Spyida Board replacement was started this week.  I'll have snipped the white wire that goes through the torrodial doughnut inside the tachometer and replaced the main PCBA with the new one.  The screws go through the heat-sinks on two transistors on the new board.  Pretty cool mounting scheme.  The male and female wires from the ignition switch and the one that runs to the +Ve coil terminal are plugged together and no longer run through the tachometer.  I have run a new wire from the -Ve coil terminal and this will plug into the new PCBA with a resistor to knock down the voltage a bit from the Pertronix Flame thrower coil and ignitor unit.  Spyida provides three resitors to try and an audio cable to run from your PC while running a wave file at maximum volume to calibrate the Tachometer at either 3K or 6K for a 4 banger.  The audio cable was missing from the kit and the engine is not back in the car yet so I haven't gotten any further with this.  But the trim ring and glasss was cleaned up and I cut a pair of O-rings I had and placed them into the groove so as to provide some squish when I remount the ring to the housing and seal up the front of the tachometer.  The white paint inside has some flakes that have dislodged so I'm deciding about what to do with the finish inside the casing.  The kit has great instructions and email with Spyida have been imediate and complete to aid in my getting this far.  There is alternative seetings concerning a jumper for use with a ignition module that has a tach-out signal so it would seem this RVI to RVC conversion will cover most all ignition systems.

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 Posted: 08-23-2013 02:17 am
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Jensen Healey
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VDO Tach: Connect to coil or MSD. Looks good but not as cool as the stock tach. $90


http://www.summitracing.com/parts/vdo-333051/overview/

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 Posted: 08-27-2013 09:55 pm
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atgparker
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Ran into a few issues with the Spyida RVI to RVC repalcement PCBA kit. The VDO is looking a bit more appealing at this point! I discovered the heatsinks which are screwed to the frame violate the swept area in which the moving coil swings about that round anular disk magnet. In operation it would swing up to about 2,500 RPM and stop altogether because of the collision. Then on the other side of the needle swing it would hit the second heatsink at around 5 or 6,000 RPM. So, I had to take it apart and snip off the corners of the tansistors heat sinks to make enough clearence. The calibration cable arrived but with the wave file playing and a 12 volt feed it isn't working. So, I'll try to calibrate the Smiths Tacometer in the car to 3,000 RPM using the potentiometer (POT) with a Suntune diagnostic meter I have assumming that its decent in as far being accurate as a Tachometer. That is if I can rig it up so I can read it in the car while the POT gets twidled on the PCBA.

The 40 miles I put on the car over the weekend with it uncalibrated. This left me with an overall impression that the electronics are a bit overly damped to stop needle bounce and therefore it lags a bit in displaying the true engine speed when trying to observe unloaded reving of the engine when I bump the RPM during down shifts and the like.

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 Posted: 08-27-2013 10:27 pm
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Dakota123
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Well that's a bit disconcerting.  I have a Spiyda conversion kit I was planning to use once I do away with points-based ignition.  (Mine did come with the calibration cable at least.)

Maybe damping is adjustable?


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 Posted: 08-28-2013 02:53 pm
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atgparker
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The Spyida conversion kits needle damping can be changed but Chris who I have been in dialog with has indicated that to do this requires changing a surface mounted capacitor.  So as the PCBA is doped with a coating of anti fouling goop it would be slightly more involved.  Chris indicated that the chosen value was used to stop needle bounce at idle and that the tachometer can read quite accurately at the calibrated value and indicate the RPM effectively while the drive train is under load.  Its the quick accelerator jabs with the clutch pedal depressed that may not get recognized as the engines response will beat the capacitors charge/discharge rate i.e. thus the needles movement is subdued to what ever that rate of change is that is dictated by this capacitor! 

Last edited on 06-15-2017 01:31 am by atgparker

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 Posted: 08-28-2013 03:42 pm
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Dakota123
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Interesting.  Thanks for being a trailblazer and figuring this stuff out.

Mike

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 Posted: 09-04-2013 10:08 pm
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answerman
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Well, my Spiyda kit arrived today. Very fast shipping considering it came from England. I'll probably try to get it swapped out tonight, we'll see how it goes. Fortunately I have a spare tach so I can use that one to get it built/calibrated etc before I actually pull the existing one out.

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 Posted: 09-05-2013 08:57 pm
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answerman
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The board swap went just fine, had the tach disassembled and rebuilt in about a half hour. I didn't run into the issues with the transistor heat sinks being in the way (in fact they aren't even close) but I haven't been able to test it yet. Went back to the Spiyda site to download the wav file for calibration and the site was down, so I just abandoned the project for the night.

The site was back up this morning, so I was able to download the file. Taking another crack at it tonight.

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 Posted: 09-08-2013 08:00 am
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answerman
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OK, for the first time since I have owned Ms. J (almost a year to the day) I FINALLY have a working tachometer.

My experience seems similar to atgparker's. I mentioned above that I had trouble downloading the wav file from the Spiyda site, but I was able to get it yesterday. I temporarily hooked up the tach directly to the battery with a wire to the coil minus. However, I could not get the calibration to work with the cable. Maybe my laptop isn't loud enough.

Anyway, today I went out to Harbor Fright (yes that's how I spell it) and picked up an automotive multimeter that, among other things, has a clamp-on attachment to read RPMs (I needed to get it for my boat anyway). Hooked that up, and was able to use it as a baseline to calibrate my tach with the Spiyda board. It seems quite accurate in comparison to the clamp-on, though as atgparker noted it is a little slow to respond.

Nevertheless, I now have a stock looking, Smiths RVI1439/03A tach in my dash with RVC internals, and connected in the RVC way, which was my goal. I just plugged the two wires that connected to the internal loop together (they were thinking, making one a male bullet and one a female) to bypass the tach that way, and ran a new wire from the tach directly to the coil. Works nicely. Even though I have the stock ignition with points, I think this is a more effective, reliable way to connect the tach (plus now I'm covered if I do go to Pertronix at some point), and I would recommend the Spiyda board to anyone with tach issues.

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 Posted: 06-13-2017 10:52 pm
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dbeliveau74
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Greetings, I have an electromotive XDi ignition systen installed by the previous owner. Nice system no more distributor under the delorto carbs. But the tach now only goes to 3000 rpm and won't read any higher. On the tach body is written Modified for HPV-1 or Tec.
I was wondering if anyone had any ideas?
Thanks,
Dan

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 Posted: 06-15-2017 01:28 am
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atgparker
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I wonder if the modification to the tachometer has interferences like I discovered with the SPIDA kit? You would have to disassemble the tack and look inside to see what's going on.

Last edited on 06-15-2017 01:32 am by atgparker

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 Posted: 06-15-2017 06:53 am
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Tom Bradley
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Hi Dan,
Do you know if the tach is reading correctly at the lower RPMs? The XDi ignition system uses two coils for a 4-cyl engine instead of one. So if the signal to the tack is only coming from one coil, the RPM reading will be 1/2 of the actual engine speed unless the tach has been modified to account for this or if the XDi system is sending a separate (composite) signal to the Tach. In the latter case, the tach may be maxing out because the signal is too low and it is not picking up all the pulses at the higher rates. Possibly the tach has a sensitivity adjustment or the XDi has a signal level adjustment to correct this.

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 Posted: 06-16-2017 04:23 am
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dbeliveau74
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I was informed of the tach malfunction by the owner when i picked it up. He made it sound li!e this was a new issue.
He did the restoration/upgrade 20 + years ago.

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