Balmar MC-614 tachometer circuit

[sv.antea]

I have had MC-614 working with a modified Delco S12 on a Universal 3cyl for years and recommended the gizmo to many friends. I found the programming section of the manual somewhat cryptic, but to be fair, I did not go into it too deep.
A friend had MC-614 installed at a yard and had problems with charging. So I charged in and corrected and cleaned up the wiring. Fixed the charging problem, but now the tachometer (operated off one of the corners of the stator via the MC-614 terminals #13 and #14) quits when the batteries are full and the regulator dials back the field current.
On my own boat, I recently converted to a serpentine belt and added a tachometer. Found a small one the size of standard temperature and oil pressure gauges that fit beautifully. Same thing, when the batteries are full and particularly when the solar panels are on, the alternator kicks back and the tach quits.
I have always assumed that the MC-614 tach pass through was designed to allow the pulses or whatever the waveform is (oscilloscope would be nice) to keep the tach working even when the alternator is not putting out much.
On one of the older CF threads circling this issue, someone asked if anyone knew what the signal leaving the MC-614 looks like, (oscilloscope would be nice), and proposed to build a circuit to boost the signal from the alternator as needed, but got no answers.
I re-read the latest edition of the manual, and there is something that seems to be implying that the circuit somehow makes sure that the fieled current never goes to zero, that insuring some ~V output from the stator. Maybe I read it wrong? It sez:
""When an electric tachometer is used, the alternator’s stator output will provide the electrical pulse needed to drive the tachometer. The MC-614 has been designed to provide regulated tach output ...""
It goes on elsewhere:
""
When the tachometer is connected via the MC-614, the regulator will ensure that the tachometer will not discontinue supplying field current when the batteries are fully charged.""
Talk about cryptic. Since when is a tachometer supplying current anywhere?

Anyone solved the problem or knows why it cannot be solved?

[smac999]

The tact will only stop if the alt stops. So the mc14 is not throttling down. It is stoping. Likly the batteries are full and solar is also on, at a higher voltage setpoint then the alt.

Next time it happens. Turn a bunch of stuff on. Lights etc). Tact will probably comeback.

Set the solar voltage lower then the alt voltage and maybe the alt won't shut off

[Jacko]

SV Antea Yep have the same prob the alt turns off because the Solar tops batteries up to higher level. been like this ever since new motor installed with electric tacho. It comes back on when power drops or I flick the power switch to the Alt. I have an ear for the sweet spot of the motor so can live without the tacho Cheers

[sv.antea]

Thanks friends, that makes sense. Next time the tachometer drops off, I will check the field current percentage reading on the MC-614, note the voltage and turn off the solar. My autopilot is almost always on, that should be enough load? Next I can check what happens when the fridge kicks in etc. Should have done that before posting.
Still my question is: what is the tachometer circuit in the MC-614 accomplishing anyway? It comes back to the "oscilloscope would be nice", that is what do the stator tap and the MC-416 tach output wave-forms look like.
Once upon a time, there was a tach on Antea. Used the circuit from an MGB tachometer, fed it pulses from a reed switch and two magnets on the flex coupler and read the RPM on my cockpit Radioshack V-meter. There was a toggle switch to select battery voltage or RPM. It actually worked for a while, lol.
I looked into the TinyTach, a diesel tachometer that works off a microphone clamped on one of the injection tubes, but wasn't sure it was waterproof, besides not being analog and round, it would not go with my cockpit decor.

[kryg]

I gave up trying to make the MC 612 connection work.

I solved the problem with a magnetic driven tacho I purchased 5 years ago. It receives the rev signal via a button magnet is stuck on the the crank pulley there is a censer that is mounted in front of the pulley that picks up the magnetic pull as the crank pulley turns, the censer wire leads back and is connected to the tacho mounted on a bulkhead facing the cockpit so anyone can read it, The tacko is powered by the boats 12 volt battery when I start the engine.

Very simple with large red readout rev, numbers, I mounted the engine panel on a bulk head just inside the companion way facing out - I can read the tacho 10 feet back from the cockpit, showing exact revs.

Originally Posted by sv.antea

I have had MC-614 working with a modified Delco S12 on a Universal 3cyl for years and recommended the gizmo to many friends. I found the programming section of the manual somewhat cryptic, but to be fair, I did not go into it too deep.
A friend had MC-614 installed at a yard and had problems with charging. So I charged in and corrected and cleaned up the wiring. Fixed the charging problem, but now the tachometer (operated off one of the corners of the stator via the MC-614 terminals #13 and #14) quits when the batteries are full and the regulator dials back the field current.
On my own boat, I recently converted to a serpentine belt and added a tachometer. Found a small one the size of standard temperature and oil pressure gauges that fit beautifully. Same thing, when the batteries are full and particularly when the solar panels are on, the alternator kicks back and the tach quits.
I have always assumed that the MC-614 tach pass through was designed to allow the pulses or whatever the waveform is (oscilloscope would be nice) to keep the tach working even when the alternator is not putting out much.
On one of the older CF threads circling this issue, someone asked if anyone knew what the signal leaving the MC-614 looks like, (oscilloscope would be nice), and proposed to build a circuit to boost the signal from the alternator as needed, but got no answers.
I re-read the latest edition of the manual, and there is something that seems to be implying that the circuit somehow makes sure that the fieled current never goes to zero, that insuring some ~V output from the stator. Maybe I read it wrong? It sez:
""When an electric tachometer is used, the alternator’s stator output will provide the electrical pulse needed to drive the tachometer. The MC-614 has been designed to provide regulated tach output ...""
It goes on elsewhere:
""
When the tachometer is connected via the MC-614, the regulator will ensure that the tachometer will not discontinue supplying field current when the batteries are fully charged.""
Talk about cryptic. Since when is a tachometer supplying current anywhere?

Anyone solved the problem or knows why it cannot be solved?

[ZULU40]

Originally Posted by sv.antea

When the tachometer is connected via the MC-614, the regulator will ensure that the tachometer will not discontinue supplying field current when the batteries are fully charged.""
Talk about cryptic. Since when is a tachometer supplying current anywhere?

Anyone solved the problem or knows why it cannot be solved?

if your connections are a bit dud the tach can show 0 RPM
this is the same effect as no power to the tach, which it seems to me to be what theyre trying to say

sometimes you can get out of it with a good dose of RPM, say 2000
same goes for some regulators

[Stu Jackson]

Never had this problem with an MC-612. I do get a lot of "how come my tach isn't working?" questions. That's when they've been plugged in all week and start their engines on full batteries. Turn on a load. This is not mission critical. I also like the idea that one respondent had of knowing the sweet spots on your engine. After 20 years I can tell you the rpms on my engine when I'm blindfolded.

Most of the time our banks need input. These days, with lots of solar, so many folks have more power than they can use. This is just an outgrowth of that phenomenon.

[wrwakefield]

Antea,

I have not experienced the tach going offline with our Balmar 614 excepts when the last 614 died... As others have mentioned, you may likely need to adjust battery full voltages on other charges sources [e.g., solar] to be slightly [e.g., 0.1v] below that set on the Balmar. [Mine are, and this may be why I haven't experienced this yet- or, most likely, my batteries are never fullly charged...]

And I agree regarding the cryptic Balmar manual. [It hasn't changed in 25+ years I've been using their regulators, and it still contains the same errors as the originals.]

To counter that, Marine How To [Mainsail on CF] recently published a great guide to programming the Balmar 614. [In case you weren't aware...]

Best wishes sorting it out.

Cheers! Bill

[Jd1]

For what it's worth, if there is no alternator field current then there is no output and no tach signal. The 614 should never reduce drive so much as to have zero output. My 614 for example rarely or ever looses tach signal with a standard lead acid battery as the battery can always take some current.
I do not know what happens with other battery types.
Lithium battery systems can cause an issue if the battery controller decides that battery is full and disconnects the batteries from the alternator.

[patprice]

My Ample Power Smart Alternator Regulator also stops the tacho when the batteries are charged. A temporary load, like electric bilge pump, will bring the tacho back up. Temporarily.
A mild nuisance offset against better charging.

[Jerry Woodward]

I am considering getting a Balmar MC-614 and I will be real upset if my tach does not work, even intermittently. I don't consider it a mild nuisance.



I have two engines on my cat and they are fairly well insulated. So it is pretty hard to use sound to gauge RPM. More importantly, if one engine quits and the other is still running, it isn't obvious. This could cause several serious situations. I rely on my tachs all the time.

[sv.antea]

I did do just fine without a tachometer for decades. But I was so happy I finally found a tachometer that is the same form as the standard engine gauges, because the larger tachometers don't fit the engine controls cubby on Yankee 30. Also, my engine is forward, just behind the mast and I can't hear it in the cockpit when the boards are in in foul weather. Also I am an instrument kind of guy.
I was looking for a small 2 1/8" dia hole gauge tach since I bought the boat (in 1980), always looking for one that can count the teeth on the ring gear. Alas, only alternator driven one is available in that format.
If you have room for standard / large tachometer, by all means avoid installing alternator driven one. They are more accurate, too. Some engines have tach pulse generators, others can be retrofitted with teeth counter sensor like all Yanmars have. And then there is the Tiny Tach.
As for a minor inconvenience, it isn't if you have solar, AGM batteries, or worse: LiFePO bank (in which case the alternator will have to shut down for long periods of time). Lol, sounds like we have a MC-614 /alternator driven tach support group going on here.
So my real questions are:
1. What is the tachometer circuit on MC-614 supposed to accomplish and what, if anything does it accomplish? Is it supposed to amplify some residual ripple, or make sure there is some field current left?
2. Does it do more harm than good? Did anyone try to not use it and leave the tach connected directly to one corner of the stator. There should be some residual ripple there when the field current goes to zero but it may be too weak. Or how much field current would be enough to make the tach work? A resistor, maybe with a diode, supplying such minimum field current when the engine is on?
3. What kind of signal / waveform would be adequate to generate by other (circuitry) means to make a tachometer designed for alternator input work?

[Jerry Woodward]

Originally Posted by sv.antea

They are more accurate, too. Some engines have tach pulse generators, others can be retrofitted with teeth counter sensor like all Yanmars have.

So are you saying that all Yanmars use a teeth counter tach and not alternator driven tachs? I have Yanmar 2GM20Fs and I'm embarrassed to say I don't know how the tachs are driven. If it is a teeth counter sensor like you say, that is good news.

[sv.antea]

Jerry, with the Yanmars. All the Yanmars I have worked on had the ring gear teeth sensor. I can't be sure yours do, check the bell housing or look at the engine wiring diagram.
I was considering buying the Yanmar tach and sensor, but Yanmar parts prices are exorbitant.

[sv.antea]

Ok, in the MC-614 manual, the crazy sentence about the tachometer supplying the field current would start making sense if you replace the word "tachometer" with "voltage regulator". Then it would mean to me that some field current is maintained by the MC-614, just enough to make the tach work. I still need to catch what the display says when the tach goes off. Fe = ?.