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Kohler 12 RES Installation


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  #31  
Old 11-29-2018, 10:37:12 AM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler 12 RES Installation

Zaphod, please post back here and let us know what the problem turns out to be. Thatís how we all learn

Bill
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  #32  
Old 11-29-2018, 05:51:00 PM
zaphod zaphod is offline
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Default Re: Kohler 12 RES Installation

Well, I figured this generator is powered by infinite improbability anyway. I'll tear into the electronics tomorrow. It starts and runs but only generates 52 volts now, so I think something in the output side went kablooey. I'll check the brush resistance and get back to you all manana - I'm in Maine and it's windy out tonight.
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  #33  
Old 11-30-2018, 02:41:59 PM
zaphod zaphod is offline
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Default Re: Kohler 12 RES Installation

Quote:
Originally Posted by zaphod View Post
Well, I figured this generator is powered by infinite improbability anyway. I'll tear into the electronics tomorrow. It starts and runs but only generates 52 volts now, so I think something in the output side went kablooey. I'll check the brush resistance and get back to you all manana - I'm in Maine and it's windy out tonight.
OKAY: I got into the box, disconnected the FN ands FP leads from the SCR. Resistance is 3000 Ohms. No voltage when gen starts AC or DC (normal). If I had to guess I'd say the SCR has shit the bed. 55 Volts when running before UU shutdown. Any thought? I'd have to cut the screws holding in the panels obstructing the brushes, so I'm hoping I don't have to go there.
Cheers,
Zaphod
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  #34  
Old 11-30-2018, 04:54:09 PM
Birken Vogt Birken Vogt is offline
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Default Re: Kohler 12 RES Installation

3000 ohms on the wires going to the generator? Or on the terminals of the SCR?

The SCR is tested differently. Like a diode. I'll look for the procedure later if you like.
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  #35  
Old 11-30-2018, 07:02:53 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler 12 RES Installation

If that 3,000 ohms is the field resistance measured through the brushes, then you definitely have a problem with the brushes. No way should the field be up in the kilohms like that.

Bill
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  #36  
Old 11-30-2018, 07:36:54 PM
Mark Dieckmann Mark Dieckmann is offline
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Default Re: Kohler 12 RES Installation

Sorry I haven't been paying attention. Those SCR's can fail. I don't recall the test procedure. Also there is a test where you feed battery voltage into FN and FP and check output. I don't recall what the output should be but it will confirm that the problem is elsewhere and not the alternator itself. I may be able to look up the test procedures if you don't have them.
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  #37  
Old 11-30-2018, 08:05:27 PM
Birken Vogt Birken Vogt is offline
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Default Re: Kohler 12 RES Installation

The output will be roughly 1/2 normal if you feed battery to FP and FN. You will also get 50-100 volts on 33-55 IIRC, something like that.

But we don't know where he got the 3k yet. On the FP/FN leads or across the SCR pack?
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  #38  
Old 12-02-2018, 07:15:09 PM
zaphod zaphod is offline
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Default Re: Kohler 12 RES Installation

Quote:
Originally Posted by Birken Vogt View Post
The output will be roughly 1/2 normal if you feed battery to FP and FN. You will also get 50-100 volts on 33-55 IIRC, something like that.

But we don't know where he got the 3k yet. On the FP/FN leads or across the SCR pack?
Got the resistance on the FN/FP leads. I ____ed up: it's actually around 300 Ohms.
Tested the SCR like a diode and have a dead leg on the + side so I figured 55 volt output was half the 110 nominal it should be channeling. Things are pretty gnarly in there: I sprayed the board, plugs and connectors with water dispersant then cleaned off the terminals. Amperage means resistance so I think something is impeding flow. My thinking is: I got 120+/- at first then 240 (open circuit unregulated) then 55. Feels like a thermal breakdown and the only part of the circuitry subject to thermal flux is the SCR. Am I right? It's going to cost $110 to find out. If I'm wrong I have to tear the generator case down to get at the brushes and windings. Doesn't "feel" like a winding as the low voltage is constant and no smoke, no heat from the generator casing but I will defer to more informed opinions.

Quote:
Originally Posted by Mark Dieckmann View Post
Sorry I haven't been paying attention. Those SCR's can fail. I don't recall the test procedure. Also there is a test where you feed battery voltage into FN and FP and check output. I don't recall what the output should be but it will confirm that the problem is elsewhere and not the alternator itself. I may be able to look up the test procedures if you don't have them.
The SCR can fail. If what I've read is true they do so catastrophically. I have a dead leg on one side. I don't have thyristor testing equipment but on a rudimentary level I think I can tell if it's pooched.. Cheers.
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  #39  
Old 12-02-2018, 07:22:03 PM
Zephyr7 Zephyr7 is offline
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Default Re: Kohler 12 RES Installation

Not all multimeter diode checkers run enough voltage to check some thyristors (fancy term for SCRs and triacs). You might read bad even if itís not unless your tester is running maybe 4-5v+ for the test.

I still think you have a problem with the brushes.

Bill
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  #40  
Old 12-02-2018, 10:04:43 PM
Birken Vogt Birken Vogt is offline
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Default Re: Kohler 12 RES Installation

300 ohms is no good, stop there, do not mess with the SCR until you have the brushes sorted out.

You need to get the back and side off and take off that housing around the brushes and see what is going on in there. Don't do anything else until you have this part figured.

Brushes should be 5-15 ohms or something like that.
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