Ducati 160 Electrics question(s)

[DewCatTea-Bob]

" I'm going to wire the switch so turning it counter-clockwise is "on" and leave the handlebar switch as it was meant to be. "

____ I agree that the handlebar-switch is best for handling the functions which it was meant to, but then what will you have the headlamp-switch do exactly? _ (As it seems it can turn-on something, turned either way.)


" I'm spending way too much time thinking about the "parking light" setting as it will never be used. "

____ The 'TOWN'-lights / "parking" setting indeed could be more useful if you jump-wire the low-beam to the connection for the small internal bulb, then you could have headlighting with engine not running! _ And you could (for one option), use the clockwise connection of poles "4" & "5" to make that jump-connection, if you so choose.


" Today I was looking at the stock diode and while it looks intact, I want to replace it. "

____ Good thinking! _ Even if it's still good as new, every stock unit that I ever checked-out, measured fairly weak (by 1970's standards) !


" It's mounted on a board that would need to be modified to fit the new headlight shell, and it just doesn't make much sense to me to modify a 45 year old part when I could put a new one in just as easily.
Domiracer has the diode listed for something like $14. Checking an electronic supply place lists a bunch of different diodes at much lower prices. I'm guessing the Domiracer part is a direct replacement for the old one, which I don't need since I won't be using the old board. So my question is...
How do I know which diode to buy, as in, what sort of specs would it need to meet? "

____ I sure wouldn't pay that much for any such original-junk, and unless somebody is intent on totally completing a 100%-restoration, then it would be totally senseless to choose an original-diode instead of a modern unit! _ (So certainly let Domi keep them for those who are bent on 100%-restoration.)
__ An original type diode should have specs of 100peak-inverse volts, & at least 2-amps. _ However in your case, instead of getting such a plain 'diode', I suggest that you just use an easy to mount (& cheap) bridge-block, (as seen in your Feb.11th posting),, and mount it somewhere near the battery's location, (as there's really no need for having any rectifier inconveniently placed within the headlamp).


Fun-Cheers,
DCT-Bob

[JimF]

The diode has a rating called PIV or Peak Inverse Voltage. This should be a number much higher than any voltage the system is ever going to see. This is the voltage at which the diode will break down when it is reverse biased. I am thinking that a common rating is 50 PIV and that would be enough for the job on a 6V Ducati motorcycle.

The diode is also rated in nominal amps which are going to pass through the diode when it is forward biased. I must admit now that I failed to read where this diode is going so I don't know how many forward amps you need. The more amps though, the bgger the diode gets. It's not altogether unwise to just pick a diode that is the same physical size as the one you are replacing as there is a good chance they will be rated at about the same forward amperage.

Jim

[ajleone]

Found a replacement diode with the same physical "footprint" as the original one - a TRW schottky/rectifier diode TRW SD31. This is rated50V 30AMP and I also found a supplier on line:

http://www.electronicsurplus.com/com...oduct_id=94762

Here's a picture on the small fiberboard that mounts inside the headlight shell: http://www.coolitalianbikes.com/250-TRW-diode.jpg

Regards,
Tony

[DewCatTea-Bob]

____ Sorta seems that I ought to help clarify some additional FACTS concerning diode-rectifiers for use on so-called "6-volt" DUKEs.....
__ I've used std.volt-meters to measure the maximum AC-voltage output of the alternators on most every OHC-single -('DUKE') model... Max.voltage ranged from about 50 to 80 RMS-volts -(for comparison, std.house-voltage is 110 to 130volts 'RMS' ! ) _ And "RMS" (RootMeanSquare AC-voltage) is considered to be the AVERAGE-voltage outcome of the std.AC-waveform, (that's fairly equal to the equivalent DC-voltage, [concerning 'resistance' loads, only]).
But in reference to diode-specs, "RMS" voltages need to be multiplied by the square-root of '2' in order to figure the 'PEAK'-voltage which a diode must stand-up against! _ Thus in order to be sure that a suitable diode will be able to maintain it's job on any stock DUKE model, the diode involved should have a PIV of at least 114-volts!
However in the case of the stock 160's relatively weak charging-circuit, a rating of 71-PIV should be quite sufficient for the involved diode's job, but, since diodes aren't made to meet such irregular specs, ya then have to choose an available unit which has what-ever diode-specs that'll cover -(even though exceed) the voltage & amperage figures which your required diode must contend with !
Likewise if ya can get a diode/rectifier unit with 100-PIV for a couple-bucks, or another with 200PIV (that's under just a buck -[1$] more, [and either choice can handle your minimum required amperage]), then ya could simply let your choice be determined by which-ever unit is easiest to get mounted (within your 160-charging project)!
___ What happens if a diode is subjected to conditions greater than it's rated-specs, ya may wonder!? ...
Well, when a diode's valve is performing it's job of preventing electrical-juice from REVERSE-flowing, and that juice develops excessive peak-pressure -(voltage-peaks that are more than 10% higher than the diode's rating), then the reverse-current will FORCE it's way though the diode-valve anyhow! _ And once that has occurred, the diode will then never be as good as it was when new! ... As it's valve will no longer be able to stand-up against the voltage/pressure which it was originally rated to handle,, or it may quit working all-together, by acting like either a 'short' or an open-circuit.
__ If a diode is simply exposed to a short-circuit and thus is then subjected to excessive forward-current-flow -(amperage that's over 10% greater than the diode's rating), then the diode will overheat & perhaps burn-out -(and that would then make it act as an open-circuit, [rarely as a short] ).
When a new diode is working near it's rated capacity, it will feel quite warm to the touch, but if it feels burning-hot, then something's not right!
Also, a diode's normal current-rating is set for room-temp operation, and so could handle somewhat higher juice-currents if kept cool, (such as by heat-sinking to metal kept below room-temp).

____ Furthermore, about "6-volt" DUKEs... The ONLY thing about any narrow-case model that's ACTUALLY '6' volts, is the 6volt-BATTERY & 6volt-lightbulb-FILAMENTs !
NO other part on any of them is really set at exactly '6-volts', not even the heavy so-called "voltage-regulator" black box which has "6 Volt" labeled right on it's side!!
Anything other than the 6-volt battery, is simply 'RATED' at 6-volts!


Enlightened-Cheers,
-Bob