Dynamo and regulator wiring

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ddclutch
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Joined: Tue Mar 12, 2019 7:50 pm
Location: nr. Kendal, English Lake District

Dynamo and regulator wiring

Post by ddclutch » Mon Apr 15, 2019 9:05 pm

Cropmaster March 1949 Petrol/TVO. Magneto ignition. Electric start. Lighting.
PO had it fitted with a 12v battery and connected negative earth which is as shown in the wiring diagrams in the owners Handbook. We had it started and running at the weekend and it sounds sweet! But the wiring in this tractor is largely missing or in tatters so I need to replace pretty well all of it.

Starting from the dynamo which I understand is gear driven. It has what I think is a Ducellier regulator fitted directly on top of the dynamo. (see photo) Three wires from the dynamo emerge from beneath the control box. 2 are connected to 2 external and rather corroded terminals of the control box. There is a third external terminal with nothing connected. The third wire is dark green and is just severed at about 6" long. Nothing else remains of it. I don't know if this should be the feed to the Ammeter via the fuse.
Can someone advise me on what the wiring in that area should consist of.
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IMG_20190414_111342827b.jpg (156.7 KiB) Viewed 648 times

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rid54
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Re: Dynamo and regulator wiring

Post by rid54 » Mon Apr 15, 2019 9:25 pm

The safest way is of course to get familiar with the wiring diagrams and see what needs to be put in place/renewed/removed etc. Assuming the generator is suited for a 12V, negative earth setup, the original schematics should be useful. Generally speaking, generators have voltage control (to keep system voltage at sutiable level with engine running), current dontrol (to avoid burning the generator out by overloading it) and reverse-current cut-out (to avoid emptying the battery when the engine is at standstill). These functions are governed with the help of the solenoid/contact setups shown in the picture. The secret is in finding the correct terminals... Usually there is a terminal for a warning light as well as the ones involved in generator control. Not unusually, control box terminals are labelled on the box cover or somewhere on the bottom plate. These markings should ideally be found in the wiring diagram as well, making connections easier. Someone with proper knowledge of vehicle electrics might be of good help here, if you do not feel quite confident about the setup yourself. Many proficient mechanics balk at electric installations.

In this case one might guess that the empty terminal is the battery connector, but that is a guess. A marking would probably be B+ or something at the terminal. Many regulators of that age use D+ for generator output, and DF for feed to generator stator winding (Field). But without markings things get trickier and you would have to rely on info about the original setup (wire colours and placing etc).

ddclutch
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Location: nr. Kendal, English Lake District

Re: Dynamo and regulator wiring

Post by ddclutch » Mon Apr 15, 2019 10:45 pm

Thanks. I have the wiring diagram from the owners's handbook which shows a single wire from the dynamo going via a fuse and ammeter, to the battery. Unfortunately it doesn't show the detail of the control box or its connections, and isn't even labelled on the diagram, though clearly there must have been one!
I was a bit surprised to find a ducellier control box on this tractor. I would have expected it to be a CAV or Lucas item. Maybe it isn't original.

In the photo you can see the two wires connected to the front 2 terminals. They look original, with proper ring terminals on each wire. The third wire is the one diasapearing front lower right of the photo. It is too long for it to have been connected direct to the third terminal so maybe it went to the ammeter. But as it emerges directly from the dynamo casing it doesn't seem to be an output from the control box, as one might expect.
I was hoping someone might have a similar set up on their tractor.

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db2d
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Re: Dynamo and regulator wiring

Post by db2d » Mon Apr 15, 2019 11:36 pm

The dynamo will be six volt, there are twelve volt versions but these were only fitted to industrial tractors. The original regulators became obsolete sixty years ago. The regulator pictured is not a DB fitment. The regulator was replaced with one mounted on a plate on the fuel tank mounting position. Suitable six volt regulators are available with bullet type connections from davidbrownparts.com Wiring is simple once the D and F wires are identified, the third wire has to be earthed.

ddclutch
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Location: nr. Kendal, English Lake District

Re: Dynamo and regulator wiring

Post by ddclutch » Tue Apr 16, 2019 3:52 pm

That puts the cat amongst the pigeons!
The tractor came to us with a 12v battery. It starts and runs with that battery so the starter must surely be a 12v one as well. It is Magneto so the battery isn't really relevant once running, but it would surely have needed a 12v dynamo as well. It is also positive earth, which is what I would expect for a pre 1962 UK vehicle, although the contemporary Owner's Handbook that we have for it has schematic diagrams which only show negative earth systems. Perhaps the Handbook is from an export model? The schematic only shows a single wire from the dynamo; perhaps these dynamoes use permanant field magnets?
The Voltage regulator looks very much at home where it is mounted. Assuming it is a replacement one it was fitted very professionally very many years ago. We know that the tractor had some refurbishment work done on it by the original supplying DB agent who bought it back off the first owner when it was 10 years old (1959). It was then sold to a second local farm where it stayed until owner #3 bought it 22 years ago. If this just needs reconnecting then I wouldn't be inclined to change it for the DB replacement version that db2d describes. Its been there long enough to be part of the history of this particular tractor even if it isn't "original" DB

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rid54
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Re: Dynamo and regulator wiring

Post by rid54 » Tue Apr 16, 2019 8:12 pm

A 6 V starter will work with 12 V supply, but it may suffer over time, because it is overloaded. With a magneto ignition, the battery will serve several start attempts before it is depleted, even if there is no charging, because there is no drain unless the lights etc are in use.

Dynamos (meaning DC generators) of that age need to have electromagnetic stator magnets, because that is how they are regulated - the field strength is governed by the regulator to give correct output from the generator (or dynamo). The regulator works with two parameters, the system voltage (usually set to 13.5 to 14 Volts) and the maximum output current that the generator can give (a design value).

A dynamo can be adopted to fit either positive or negative ground, but it may require internal surgery to shift connections around, best left to a specialist. I'd expect the regulator to need some work as well. Re-building a dynamo for another system voltage might possibly be possible, but probably not really an easy thing to accomplish.

The regulator in your pics looks at home, as you say. It probably came with the dynamo.

ddclutch
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Location: nr. Kendal, English Lake District

Re: Dynamo and regulator wiring

Post by ddclutch » Tue Apr 16, 2019 9:03 pm

Yes, it needs more investigation.
I have no intention of attempting to change the polarity. Positive earth is what I would have expected, seems fine to me and it spins the starter in the right direction so that is how it will stay. I was just puzzled that the diagrams in the hardbacked Owner's Handbook we have (an original copy) all show negative earth schematics. They also only show a single wire connection to the dynamo, which is equally puzzling.

Its entirely possible that the whole system is still 6v, but that the PO used a 12v battery to give a better spin when starting. And as the dynamo and lighting wiring is missing he may have relied on just topping up the battery with a charger between uses which I believe was fairly infrequent. Its not been used for proper work for many years.

I need to see if I can get a measured output from the dynamo and see whether it is giving 6v or 12v.

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db2d
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Re: Dynamo and regulator wiring

Post by db2d » Tue Apr 16, 2019 10:36 pm

The voltage will be stamped on the dynamo casing. It is quite common to see these tractors using a 12V battery for starting with a 6V starter motor. This does not harm the starter in any way, in fact 6V starters were fitted on some DB tractors with 12V belt driven dynamos by the factory. The regulator pictured is not a DB modification.

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rid54
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Re: Dynamo and regulator wiring

Post by rid54 » Wed Apr 17, 2019 6:43 am

If the wiring diagrams show just one connection from the dynamo, it could be that the symbol for the dynamo sort of "includes" the regulator; as in you rpic it is possible to interpret the dynamo+regulator as one component. Or does the regulator swhow up as well in the diagrams?

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cobbadog
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Re: Dynamo and regulator wiring

Post by cobbadog » Wed Apr 17, 2019 6:48 am

We have a TEA20 which was a 6v system and now runs an 12v alternator as fitted by the previous owner. It copes easily using the 6v starter.
I have a diagram of a 6v system on a D.B. and as best I can tell shows the normal + earth.

ddclutch
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Location: nr. Kendal, English Lake District

Re: Dynamo and regulator wiring

Post by ddclutch » Wed Apr 17, 2019 9:29 am

I am increasingly of the thought that the PO simply used the tractor without lights or dynamo connected up and used a 12v battery just to get more ooomph from the starter when firing up. I will go today and look to see what bulbs are in the light fittings and if I can see any voltage marks stamped on the dynamo casing but my suspicion is that it is all an unaltered 6v system.

Here is a photo of the printed wiring diagram in the Handbook that we have. Shows a negative earth system (wrong?)
IMG_20190414_111120477b.jpg
IMG_20190414_111120477b.jpg (71.37 KiB) Viewed 547 times
no details (or even existence!) of a control box/regulator and only a single wire between dynamo and ammeter/starter/battery. So no field coil exciter wire?

I am concious as a newbie on this forum that I am using up bandwidth on a topic which is probably of limited interest to others, but I do appreciate the knowledgeable help I have had here. Many thanks.

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db2d
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Re: Dynamo and regulator wiring

Post by db2d » Wed Apr 17, 2019 10:49 am

As I have stated —there are three wires coming out of the dynamo- dynamo-field and earth. The regulator is someone’s adaption.
6V batteries are available but of dubious quality and quite expensive. The starter motor works better with a 12V battery making engine starting easier. This is a common feature on these tractors bearing in mind that only engine starting is required and a fully charged battery will start the engine many times. Few people are aware of the updated regulator and are unable to get the 6V changing system working.

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rid54
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Re: Dynamo and regulator wiring

Post by rid54 » Wed Apr 17, 2019 11:35 am

That type of dynamo cannot function in any normal system, without a regulator. It is probable, that the original setup incuded an external regulator (which is a common solution) and something happened later that caused a re-build. The wiring diagram is not very comprehensive. I still think that the symbol for the dynamo is representing the whole setup (dynamo+regulator). The diagram does show a negative earth system, though.

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db2d
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Re: Dynamo and regulator wiring

Post by db2d » Wed Apr 17, 2019 2:49 pm

db2d wrote:
Mon Apr 15, 2019 11:36 pm
The dynamo will be six volt, there are twelve volt versions but these were only fitted to industrial tractors. The original regulators became obsolete sixty years ago. The regulator pictured is not a DB fitment. The regulator was replaced with one mounted on a plate on the fuel tank mounting position. Suitable six volt regulators are available with bullet type connections from davidbrownparts.com Wiring is simple once the D and F wires are identified, the third wire has to be earthed.
The original regulator had a single bobbin and was mounted on the dynamo. The wiring diagram is correct.

ddclutch
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Joined: Tue Mar 12, 2019 7:50 pm
Location: nr. Kendal, English Lake District

Re: Dynamo and regulator wiring

Post by ddclutch » Wed Apr 17, 2019 3:29 pm

Yes, I do understand and accept that the wiring diagram labels the dynamo, but means the combined unit of dynamo and control box. Still no idea why it is showing a negative earth arrangement though.

I went to check the tractor this morning. The dynamo has a small soft aluminium makers name plate fitted, very worn but discernable as CAV and even feinter, 6v. However, I started the engine and I am getting 13.8v measured between the chassis and the third (disconnected) wire that I have previousl mentioned. This looks hopeful but as it is without any connection back to the battery I am not sure that it would maintain this voltage when connected and not open circuit. But the dynamo appears to be producing something without any "exciter" current external input.

I then completed the wiring from this cable back via fuse box, ammeter and starter to the battery. With the engine running, the ammeter isn't responding (suspect broken, its a lucas brass bodied version, probably the original). At the battery I am getting 10.04v. Lower than I expected with 13.8 at the dynamo but the battery is definately faulty so may have a cell down. Disconnected the battery is only reading 9.6v so I will try again tomorrow with a new battery.

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