Selenium Retifier Replacement with Solid State Rectifier

[border0_3]

Hi DJM. That is really neat. I'll have to try this.
Shame I've thrown away half a dozen U/S rectifiers.

[DJM]

I hardly ever throw ANYTHING away, perhaps I should do more often but inevitably, when I have done I've wanted the thing a couple of years down the line.
After messing with CB77s for fifty years I've a whole heap of stuff but no tinware, exhausts or switchgear, just the usual junk that nobody else wants either.

Question,

How did I end up with a load of top yokes (triple trees) spare but NO bottoms

[Geoff Hastings]

Hi there, I've read most of the posts regarding replacing the original rectifier. My question is, my one had a capacitor attached to the original rectifier. I can find no reference to it on any posts or even an original circuit diagram. I can't even think what purpose it would serve, a very small amount of smoothing perhaps but not enough to make a difference. Do you think it was a factory job or someone's hot mod? It's fitted between the yellow lead and Earth.

[DJM]

Years ago, I can't really remember how many years, Lucas used a large capacitor combined with an alternator to produce a system which could run without a battery.

From memory the capacitor was just connected across the battery which could be left in place or removed at will. I think from about the same era as the zenner diode with the big cast aluminium heat shrink that used to bolt under the bottom yoke (triple tree).

The capacitor was quite a big thing, 30 mm diameter? and mounted on a big spring to avoid vibration damage.

I think it was mostly a BSA/Triumph fitment but it would have worked on any alternator equipped bike, Sounds like someone fitted the same thing to your C77 but unless you intend to take up motocross I think you can safely discard it!

I probably have a Lucas advertisement with a picture somewhere if anyone is interested.

[Geoff Hastings]

Hi Dennis, I do remember the BSA with the heat sink under the fork yoke, this thing is only .4uf so would only help with radio suppression. I'll bin it, it's more of a liability than a help. When I checked the original bridge rec it was leaky on all the diodes. I'm off to Maplins tomorrow to buy a modern bridge rec, amazing how prices for semi conductors has come down.

[G3]

OK you electronic wizards, I’m looking for suggestions before I remove my recently installed bridge rectifier and reinstall the OEM type.
So after installing the bridge rectifier (Snakeoils diagram), all seemed ok. My highest dc output was a generous 14+vdc. But, I believe I cooked my acid battery by using the tender.
New battery installed, but now I’ve noticed the dc output now off of the rectifier is pushing 17vdc at normal city speeds...not good!
So before I yank the new and in with the old, has anyone else encountered this, and what did you do to resolve it if you did?

Thanks

[Tim Allman]

OK you electronic wizards, I’m looking for suggestions before I remove my recently installed bridge rectifier and reinstall the OEM type.
So after installing the bridge rectifier (Snakeoils diagram), all seemed ok. My highest dc output was a generous 14+vdc. But, I believe I cooked my acid battery by using the tender.
New battery installed, but now I’ve noticed the dc output now off of the rectifier is pushing 17vdc at normal city speeds...not good!
So before I yank the new and in with the old, has anyone else encountered this, and what did you do to resolve it if you did?

Thanks

Actually, 17 V is right on spec. according to the shop manual.