3k Chinese alternator just stopped mid run

[tyssniffen]

ok, I get that you say the wires go back to the windings, but now that I have these little rectifiers, and a nice chunky heat sink, can anyone clue me in a bit more on which wire goes where?  I labeled my current (dead?) one, and my new one still on the bench.  see attached.   

My ability to dig under the box and figure out which wire goes to the windings is a bit low.

[ThomasEriksen]

1 -> D positive
3 -> B negative2 and 4 -> A and C alternating so it don't matter which goes where
never seen such rectifier before, 99% sure they used red as positive and black as negative

[ajaffa1]

I would agree with ThomasEriksen, red and black on the old rectifier would indicate +ve and -ve these two wires go to the field winding. The other two are the AC supply and go to the slip rings inside the generator, doesn`t matter which way around they are.

Bob

[tyssniffen]

well, hooked up as directed and no go.  Not a blip on the volt meter on the output.

Besides getting a higher quality Ohm meter (to attach to WHICH of those wires?) what else have I got?   

Could it really be that the windings just... failed? all at once, with less than 800 hours on it?

fustrated

[mikenash]

See from Bob, previously:

"Well done on ordering new rectifiers. The ones that ship with these ST heads are garbage. A few years back I did a tear down and rebuild of a brand new ST head, I posted a lot of info and pictures showing how to do it. I replaced the rubbish bearings, skimmed the slip rings which were not concentric with the shaft, replaced the cheap carbon brushes, rewired the top box and fitted a new rectifier with an aluminum heatsink. Later I fitted an automatic voltage regulator.
Aluminum heat sinks can be found on ebay and other sites, old computers all have nice heatsinks on the processor chip. Drill a hole in the back of the top box, bolt the rectifier to the inside of the top box with the heatsink on the outside where it will get good airflow

The wiring is pretty simple there are two wires that can be traced back to the slip rings, these are the AC feeds to the rectifier, it does not matter which way you wire them as long as they both go to a rectifier lug labeled AC. The other two wires go to the field windings and are positive and negative, on mine the positive was the red wire. I do not know if your wiring has spade connectors or screw lugs, fortunately the rectifiers you ordered are compatible with both."


Further to this -  I had one of these with the same experience

I simply extended all the wires with heat-shrink joiners and took all the gubbins away from that top dog-box to mount elsewhere - new rectifier etc

The bearings were crap, too, as everyone says - they rumbled and whined from new

When I took them off to replace, one end of the shaft didn't even have enough machined surface to fully support the bearing - it was so badly made.  I just fitted new, sealed, SKF/Timken bearings

Brushes were crumbly crap and one just snapped in half.  I had some local ones made

Brush-holders are lightweight, poorly-built, fiddly crap - you may have to loosen their screws and bend them around to get everything in line?

I was really reluctant to delve into the innards of it - but if you're going to own/run one of these, you'll have to get to be OK about doing that, imho

Good luck

[ajaffa1]

Hi Tyssniffen, a couple of possible causes:
1. Brushes have failed/worn out, test for continuity with ohm meter
2. Armature winding has failed, test for continuity between slip rings with ohm meter
3. Field windings have failed, remove +ve & -ve terminals from rectifier and test for continuity with ohm meter.
4. Shut down under load can remove residual magnetism from field, flash field windings with 12 volt battery to restore magnetism.

Let us know what you find.

Bob