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sparx rectifier question

2K views 4 replies 2 participants last post by  mossy 
#1 ·
i'm putting a sparx rectifier unit on a 68 bonny that i'm building from scratch.i've been told to join the black sparx wire to the brown/blue wire that supplied the zener diode.
on my new harness i have a brown/blue fused wire that goes into the harness and comes out brown/white at the other end.
should i connect the sparx black wire to the brown/white end where the zener plugged in (making the black longer), or should i just cut into the brown/blue behind the fuse?
 
#2 ·
Hi,

i'm putting a sparx rectifier unit on a 68 bonny that i'm building from scratch.i've been told to join the black sparx wire to the brown/blue wire that supplied the zener diode.
That is correct for a '71-on harness, not for a '68.

An original '68 T120 has an ammeter in the headlamp shell; the Brown/Blue wire goes only from battery -ve to one ammeter terminal, and one horn terminal.

Assuming you're actually talking about fitting a Sparx combined regulator/rectifier (i.e. a finned box that replaces both rectifier and Zener diode), if you want the ammeter to continue to show both discharge from and charge into the battery, connect the Sparx box Black wire to the Brown/White wire originally intended for the rectifier (in the underseat area).

on my new harness i have a brown/blue fused wire that goes into the harness and comes out brown/white at the other end.
I doubt it. If it really does, you either don't have a harness for a '68 T120 or you have some shag-awful 'universal' construction that's neither use nor ornament. As I say, on a correct-for-'68-T120 harness, the Brown/Blue goes from battery -ve through the fuse to one horn terminal and one ammeter terminal.

should i connect the sparx black wire to the brown/white end where the zener plugged in (making the black longer), or should i just cut into the brown/blue behind the fuse?
Neither. The Sparx Black wire should simply be connected to the Brown/White intended for the original rectifier.

The original Zener diode was in a finned egg-shaped heatsink under the headlamp. The Brown/White wire terminal to this should be taped up securely. The Red wire, that originally attached to the bolt that mounted the heatsink, should still be bolted to the bracket on the lower yoke.

Finally, the Sparx reg./rec. Red wire should be connected directly to battery +ve.

Hth.

Regards,
 
#3 ·
sparx question

thanks, will connect sparx black to rectifier brown/white.My harness is 69-70 and all connections appear to be as you said. The brown/white that I assumed was for the zener comes off one post of the ammeter. (I marked it with blue tape in pic).Should I tape this one off?


That is correct for a '71-on harness, not for a '68.

An original '68 T120 has an ammeter in the headlamp shell; the Brown/Blue wire goes only from battery -ve to one ammeter terminal, and one horn terminal.

Assuming you're actually talking about fitting a Sparx combined regulator/rectifier (i.e. a finned box that replaces both rectifier and Zener diode), if you want the ammeter to continue to show both discharge from and charge into the battery, connect the Sparx box Black wire to the Brown/White wire originally intended for the rectifier (in the underseat area).


I doubt it. If it really does, you either don't have a harness for a '68 T120 or you have some shag-awful 'universal' construction that's neither use nor ornament. As I say, on a correct-for-'68-T120 harness, the Brown/Blue goes from battery -ve through the fuse to one horn terminal and one ammeter terminal.


Neither. The Sparx Black wire should simply be connected to the Brown/White intended for the original rectifier.

The original Zener diode was in a finned egg-shaped heatsink under the headlamp. The Brown/White wire terminal to this should be taped up securely. The Red wire, that originally attached to the bolt that mounted the heatsink, should still be bolted to the bracket on the lower yoke.

Finally, the Sparx reg./rec. Red wire should be connected directly to battery +ve.

Hth.

Regards,[/QUOTE]
 

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#4 ·
Hi,

will connect sparx black to rectifier brown/white.
The brown/white that I assumed was for the zener comes off one post of the ammeter. (I marked it with blue tape in pic).Should I tape this one off?
Uh-uh, you need the Brown/White connection to the other ammeter terminal (the one without the Brown/Blue wire).

As well as Brown/White wires originally on rectifier, Zener and ammeter, you should find there's one on the ignition switch:-

. When the ignition switch is first turned on, supply is only from battery -ve, along the Brown/Blue to the ammeter, through the ammeter to the Brown/White, along the Brown/White to the ignition switch and from the ignition switch into the rest of the bikes's electrics. Then the ammeter needle is towards the "-", indicating a discharge from the battery.

. When the engine's started, at tickover the alternator (originally through the rectifier and the attached Brown/White wire) produces very little so, while the ammeter needle might move a little away from "-" and towards zero, the battery's still supplying much of the bike's electrical power, so the ammeter still indicates a discharge from the battery.

. As the engine rpm increases, the alternator is supplying more of the bike's electrical power directly through (originally) the rectifier and the Brown/White wire directly to the ignition switch, so less is drawn through the ammeter from the battery, so the ammeter needle moves closer to zero.

. At some engine rpm - depending on the electrical consumers switched on - the alternator will be supplying all the bike's electrical requirements, nothing will be drawn from the battery so the ammeter indicates zero. Above those rpm, the alternator can also charge the battery, so the ammeter needle will move from zero towards "+".

. The alternator's AC Volts vary wildly with rpm, the rectifier only rectifies AC to DC so - originally - through the Brown/Blue wire from battery -ve to the ammeter, through the ammeter, through Brown/White from the ammeter to the Zener and from the Zener heatsink through the Red wire to battery +ve, the Zener was connected 'across' the battery and - by converting excess Volts to heat - limited the AC-rectified-to-DC Volts to no more than about 15V.

Now:-

. The Sparx reg./rec. regulates the AC Volts before converting them to DC before outputting the regulated DC along the Black wire. That's why you connect the Sparx Black wire to the original rectifier Brown/White wire, because that Brown/White's already connected to the ignition switch and the ammeter, and the ammeter's already connected through the Brown/Blue wire to battery -ve. :thumb

. Also, because the reg./rec. does the Voltage regulation is why you disconnect and tape up the Brown/White wire that used to attach to the Zener.

. Finally, because both the old rectifier and Zener also had Red wires to battery +ve, you connect the Sparx Red wire to battery +ve.

Couple of caveats:-

. I've described what the ammeter should do. In practice, when the engine's running, the vibes shake the needle around and it's hard to be more than vague about what it's showing.

. It's worth connecting a short piece of wire between the ammeter terminals. The ammeter will then show only half Amps (the other half're travelling along the bypass wire) but, if the vibes ever bugger the ammeter as you're riding along, the engine won't suddenly stop, lights go off, etc. :thumb

Hth.

Regards,
 
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