Testing the Logitron regulator/rectifier

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@win
Posts: 13
Joined: Sun May 10, 2020 3:04 pm

Testing the Logitron regulator/rectifier

Postby @win » Sun May 10, 2020 4:32 pm

Hi guys, my name is Ed and i'm a long time Ducati owner. Currently i own a '79 900 GTS Bosch and a '74 350 Mk3.

The 350 being the blue/gold, non desmo version. The bike originally runs 6 volts, comes with Motoplat ignition (pick-up and transducer) and a Logitron regulator/rectifier (r/r unit).
The Motoplat ignition has been replaced by a Sachse 3.10 pick-up and ignition box and a Conti 6v transducer.

The Logitron r/r unit is still there, but i want to test it. I can't get the bike to start right now and as all the other parts are new, i'm suspicious of the r/r unit. I can't see a spark with the spark plug held onto the cylinder head. However, the bike did run with the new set up.

I read a couple of threads on Motoscrubs and got a basic idea of testing the r/r unit. So i ran a few tests, but honestly i have no idea what i'm reading there. Could you please tell me if i ran the right tests and what the measures mean? Basically i want to know if my r/r unit is still up to the job.
Thanks in advance!

Cheers,
Edwin

Testing the Logitron R/R unit

Test 1: all wires attached to r/r unit, ignition key switch off, battery attached
Test 2: all wires attached to r/r unit, ignition key switch on, battery attached
Test 3: no wires attached to r/r unit, except marrone (brown), ignition key switch off, battery attached
Test 4: no wires attached to r/r unit, except marrone (brown), ignition key switch on, battery attached
Test 5: no wires attached to r/r unit

Testing with multimeter, set to Ohm
Ground: metal casing of r/r unit.
first reading is with black tip of probe to ground, second with red probe to ground

-----------------------------------------------------------
1 yellow1 to ground 1 / -417
1 yellow2 to ground 1 / -417
------------------------------------------------------------
2 yellow1 to ground 1 / -422
2 yellow2 to ground 1 / -422
------------------------------------------------------------
3 yellow1 to ground 1 / 1
3 yellow2 to ground 1 / 1
------------------------------------------------------------
4 yellow1 to ground 70 / 82
4 yellow2 to ground 210 / 48
------------------------------------------------------------
5 yellow1 to ground 1 / 1
5 yellow2 to ground 1 / 1
------------------------------------------------------------
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ducwiz
Posts: 604
Joined: Tue May 22, 2012 12:52 pm
Location: near Frankfurt, Germany

Re: Testing the Logitron regulator/rectifier

Postby ducwiz » Sun May 10, 2020 6:05 pm

Hi Ed,

just wanted to power down my PC - but then again someone with R-R questions/problems appears ...

The Logitron is a rare item. Basically, it works the same way as the wellknown and ubuquituous Ducati 34.41.06 R-R. I worked with it many years ago on a friend's 350 SCR, and also converted it to 12 Volt. But I made totally different tests with it.
I cannot imagine which informations can be drawn from the results yo gave us. Also, for me it makes absolutely no sense to measure a resistance in an electric circuit, when an external voltage is present at the same time.

How to test an electronic 6V singles R-R (Logitron or Ducati):

step 1: check the alternator stator; a faultless stator is a precondition for a functional charging system
- measure the resistanc of both yellow wires against the red wire: values should be identical, ~ 0.5 ohms or a bit less
- measure the insulation resistance of the winding against the stator plate (which is on chassis ground / battery potential): your multimeter should show infinite resistance

If OK, proceed to

step 2: measure the AC voltages coming from the stator wdgs. while engine is running, according to the following works instruction sheet:
https://www.sendspace.com/file/kqnv29

You might not have the equipment at hand to perform the R-R test, so I suggest an easier but only basic way to check the R-R for power output.
Precondition: you succeeded with all the tests described above:

- reconnect all wires to the R-R. Your 6V battery should be fully charged. Measure the voltage across it's terminals, you should read 6.2 - 6.4 volts, or even more. Start the engine, increase rev. speed from idle up to 3000/min and more, while observing the meter's reading of the battery voltage. This should increase now, up to 7.0 - 7.2 volts. Finally switch on the headlight, engine still running. The battery voltage may step down by a certain amount for the same rpm value, but it must still show the increase effect when the engine is revved faster.

For a really precise measurement of the R-R's function you need a n AC transformer with 6 - 12 V / 3 A output, a 6 V incandescent lamp of ~10-20 Watt (brake light), and a variable electronic DC power supply with at least 8 V output, starting around zero V.
If this equipment is at hand in your house, I will provide the necessary instructions, and maybe sketch a little schamatic diagram in the next post (not today).

cheers Hans

Ventodue
Posts: 952
Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: Testing the Logitron regulator/rectifier

Postby Ventodue » Mon May 11, 2020 9:51 am

Hi Ed and welcome to the Forum,

Reading thru your post, I do wonder if you’re not getting things a little mixed up …

As I get it, the basic problem you’re trying to solve is a lack of spark? In which case, why are you bothered about the performance/non-performance of the reg/rec? The reg/rec has one purpose in life: to allow the alternator to charge the battery. The ignition system doesn’t care if it’s doing this job, or not.

If you haven’t got a spark, look at the ignition components. I guess your Sachse system works off a battery? Is it charged?

P.s Basic in-situ testing of a reg/rec is actually very simple. Turn the headlamp on and see how bright it is. Now fire the bike up and rev it up to 3,000rpm. Does the light get any brighter? Yes? The reg/rec is working. No? Well, either the reg/rec isn’t working, or the alternator isn’t working …

If you want to see how well the reg/rec is performing, stick a voltmeter across the battery terminals when revving the engine. On a 6 volt system, the reg/rec should be putting about 7.2 volts into the battery. Less, and it (or the alternator) is working below optimum. More, and it risks cooking the battery.

@win
Posts: 13
Joined: Sun May 10, 2020 3:04 pm

Re: Testing the Logitron regulator/rectifier

Postby @win » Mon May 11, 2020 1:54 pm

Thanks for your answer Hans. It's a little disappointing however, i thought i got a good thing going here!
I ran these tests after reading the following 2 threads on this forum:

viewtopic.php?f=3&t=749&hilit=6v+battery and
viewtopic.php?f=3&t=2081&hilit=starting+problems

They call it the "flip/flop"test? It is very possible i totally misinterpreted the info provided in these threads, or the r/r units mentioned in those threads work differently. Any advise is welcome because i'm sorta in the dark when it comes to testing electronic components.
A couple of tests/results i presented might be useless indeed, but there are at least two tests with no external voltage present (test 3 and 5).

I do have a brake light, a variable electronic DC power supply with at least 8 V output, starting around zero V and an AC transformer with 6-12 volt, but the latter is not putting out 3 A, only 0.7 A. I don't think that will do?

I'll run the step1 test asap. But this will tell me something about the alternator, not about the r/r unit.. i presume?

The other tests i cannot run, as the bike won't start. Once i get it running, i can run all the "basic" tests.

I really thought after reading those 2 other threads i mentioned before, that there is an easy way to tell if the r/r unit is still functioning without the bike running. I was also convinced that a functioning r/r unit would be relevant for the capability of the bike to fire up.
Ventodue covers that in his answer.

Ciao
Edwin

@win
Posts: 13
Joined: Sun May 10, 2020 3:04 pm

Re: Testing the Logitron regulator/rectifier

Postby @win » Mon May 11, 2020 2:37 pm

Thanks for your answer Ventodue.

I'm getting things mixed up on a regular base, you're not wrong there!

Yes, my main concern is not being able to fire up the bike. I checked and found no spark. As all the other components are new, i thought i first run 'an easy test' of the r/r unit. Little did i know!

I am bothered about the performance/non-performance of the r/r unit because i was living under the assumption that on my specific bike a functioning r/r unit is needed to fire up the bike.

I don't know if that has anything to do with the lack of a direct connection from alternator to transducer? In the original setup there was a blue wire going directly from alternator to transducer, but it is no longer connected since the Sachse was installed.

So for my understanding, let's assume my bike is able to run without the r/r unit. Obviously there won't be any charging of the battery going on then. It would run until the battery is empty. What would be the essential connections between battery, ignition key switch and transducer i need to run the bike? Or, how to bypass the r/r unit?

I do realise i'm asking a lot and that it is hard to explain stuff to dummies... so i really appreciate that you take the time to explain the obvious for those who have no clue about electrics.

Ciao
Edwin

Ventodue
Posts: 952
Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: Testing the Logitron regulator/rectifier

Postby Ventodue » Mon May 11, 2020 3:14 pm

Hi Edwin,

@win wrote:Yes, my main concern is not being able to fire up the bike. I checked and found no spark. <snip>

Ok, it’s important to know that. Otherwise we could be engaged on all kinds of wild goose chasing ... :)

@win wrote:I am bothered about the performance/non-performance of the r/r unit because i was living under the assumption that on my specific bike a functioning r/r unit is needed to fire up the bike.

Not normally, no.

BUT it IS possible that your Sachse unit is using the reg/rec as a connection box. And seeing as I'm not familiar with the Sachse,I can’t really respond to your next question - I don't want to lead you in a false direction ;) .
@win wrote:I don't know if that has anything to do with the lack of a direct connection from alternator to transducer? In the original setup there was a blue wire going directly from alternator to transducer, but it is no longer connected since the Sachse was installed.

Hopefully someone who is familiar with the system will come along soon. If not, try posting whatever technical info you might.

(Just for info: To produce a spark, what an ignition system needs is a source of energy. Conventionally, this can either be from a battery - same as your car. Or from an ignition coil on the alternator - similar to a leaf-blower/strimmer/small lawn mower, kinda thing. Each system has its advantages/disadvantages. What I don’t know, because I’m not familiar with it, is what your Sachse uses).

@win wrote:So for my understanding, let's assume my bike is able to run without the r/r unit. Obviously there won't be any charging of the battery going on then. It would run until the battery is empty.

Correct. This is known in the jargon as a ‘total loss ignition’. Some racers use it because they don’t want the dead weight of an alternator to slow them down, and they know they ain’t going to exhaust the battery before the race is over. (Or so they hope. It has been known to happen, however … :o )

@win wrote:What would be the essential connections between battery, ignition key switch and transducer i need to run the bike? Or, how to bypass the r/r unit?

Again, I hesitate to advise without more knowledge of how the Sachse works and how it's wired up.

ducwiz
Posts: 604
Joined: Tue May 22, 2012 12:52 pm
Location: near Frankfurt, Germany

Re: Testing the Logitron regulator/rectifier

Postby ducwiz » Mon May 11, 2020 5:31 pm

@ventodue:
The Sachse MHP ignition: https://www.elektronik-sachse.de/shopsystem-3/en/digital-ignition-zdg-3-10-6v-for-ducati-250-450.html
Here you also can download a descriptive paper with a mounting instruction sheet.
The Sachse is a battery-powered Kettering (or coil/points) ignition, where the points are replaced by a bipolar tzransistor or a MOSFet element. With an empty or weak battery it cannot put out any spark.

@Edwin:
Fine, you have the necessary equipment at hand to perform a functional test of the R-R.
The figure shows the necessary arrangement of the components mentioned in my last post. The text in the figure tells what has to be done. Don't hesitate to ask any question, if you are in doubt.
The transformer's secondary must be connected between the bulb and the R-R's case. Your transformer puts out 0.7 A/ 8 V, roughly 5 Watt, so you have to choose a bulb of the same power rating.

reg_test.jpg

The text once again, adapted for your special equipment:
How to test a DUCATI R-R 34.41.06, part no. 0608.46.750, and the rare LOGITRON R-R
==================================================================================

All information given here is without engagement, so please do the job with greatest care !

- Connect a variable DC power supply rated 0.2 Amp minimum with it's positive terminal to the "marrone" connector at the regulator, with it's negative terminal to the regulator case. Take great care not to get the wires crossed, otherwise the R-R gets damaged once for all !
- Turn the control knob to zero, do not switch power on at that time.
- Measure the voltage in parallel to the power supply with a precise DC voltmeter.
- Connect an incandescent bulb rated 6 (or 12) Volt/4 to 5 Watts to one of the "GIALLO" connectors with one terminal.
- Connect an alternating current source (AC, e. g. door bell or electric toy-railway transformer) of about 6 Volt/~1 Amp to 12 Volt/~1 Amp, corresponding to the rating of the lamp used, between the bulb's other terminal and the regulator case. The bulb should not be enlighted now, otherwise the corresponding SCR in the R-R is faulty.
- Switch on DC power and slowly increase the voltage -> slightly above 4.5 Volts the bulb must light up.
- Reaching 6.8 to 7.2 Volts the bulb must switch off again. Take care not to exceed 7.5 - 8 Volts for more than a few seconds, else the regulator may be damaged.
- Repeat the procedure on the second "GIALLO" connector. If the bulb always behaves like described above, the R-R is O. K.


And finally, for those who can read schematics for electronic circuits:

reg_circ_web.jpg

This is what is hidden inside the DUCATI R-R (except the center-tapped coil, which is in fact the stator winding inside teh engine).
The Logitron R-R's interior parts might be similar, but I have no documentation for it.

cheers Hans
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Ventodue
Posts: 952
Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: Testing the Logitron regulator/rectifier

Postby Ventodue » Mon May 11, 2020 10:46 pm



Thanks, Hans. Had actually just found that myself, browsing tonight.. ;)

@ Edwin: in the search for a spark, have you put the Sachse unit into test mode as described in the instructions? This has got to be your first step.

Note, as Hans says: it's a battery powered system which, according to Sachse, needs to be kicking out at least 4.6 volts to work. Measure this, not at the battery, but between terminals 2 and 6.

Ciao

Craig

@win
Posts: 13
Joined: Sun May 10, 2020 3:04 pm

Re: Testing the Logitron regulator/rectifier

Postby @win » Tue May 12, 2020 12:23 pm

Brilliant!! Thank you for the test circuit, that is very useful. I'll be putting that test set-up together next weekend, if my AC transformer can be used:

I have two AC transformers available, but as i just found out (sorry for the earlier misinformation) both are putting out more than 12 volt.

1) 16 Volt /~ 0,7 Amp
2) 14 Volt /~ 1 Amp

Can the excess of voltage for this test be compensated by the use of a incandescent bulb with a higher wattage?

Thank you for clearing up my misunderstanding about the function of the r/r unit. I will still test it, but i now understand the r/r unit plays no role in firing up the bike. There is a red wire going from the battery directly to the ignition key switch.

I attached the wiring diagrams i made myself for reference. Have a good laugh over it, but remember i have no education or training in electronics whatsoever! One with original Motoplat wiring, a second one after the Sachse conversion.

Now we got the r/r unit out of the way, i can shift to other components in my search for a spark.

Meanwhile, and of course i should have checked that first, i found out that my 6 volt Energysafe battery is severely crippled. It won't give more than 4,5 Volt, which is just too little to activate the Sachse system.

I tested my Sparcon 6 volt trickle charger not connected to the battery and it appears to put out 9 Volt. So all winter my 6 Volt battery has been fed with 9 Volt? Or is the thing supposed to put out that much Volt initially and scale down accordingly to the demand of the battery?
Hooked up to the battery, the charger wont put out more than 4,5 Volt.
Tried to charge the battery with a different, old school -non trickle- charger with variable voltage, but all red warning lights it has light up when the voltage exceeds ca. 4,5 Volt.
Kind of confused here. Is a 6 Volt charger supposed to put out 9 Volt when not connected to a battery?

Ordered a new (conventional lead acid) battery this morning. Comes uncharged, so i have to charge it myself. Before ruining another battery i need to know if my (preferred) 6 Volt trickle charger is in good order..

Once i have a fully charged battery in good condition, i will continue the testing.
As a first step i will put the the Sachse unit into test mode. Good suggestion!
I suppose, with the Sachse unit in test mode, i have to hold the spark plug onto the engine to ground it?

When that works out well and i find a spark, get the bike running (assuming nothing else is wrong with fuel supply and/or carb), i will dive into testing the charging system, as you pointed out.

Thanks for putting me into the right direction guys!

Ciao,
Edwin
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Ventodue
Posts: 952
Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: Testing the Logitron regulator/rectifier

Postby Ventodue » Tue May 12, 2020 5:24 pm

@win wrote: I suppose, with the Sachse unit in test mode, i have to hold the spark plug onto the engine to ground it?

Eek! Yes! Bloody Sachse forgot to include THAT minor detail in their instructions, didn't they?! You'll be waiting along time if you don't ... :?

(Mind you, I found their instructions littered with irritating inconsistencies. Ok, we can all work it out in the end - I hope. But when even the box itself is sometimes called a ZDG3, then elsewhere a ZDG3.1, a ZDG3.10, or a ZDG3.12, you have to wonder if anyone bothers to proof-read this stuff before they hit print.

There, rant over ... :) )


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