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Kohler 33rz high output part 2

toddbailey

Registered
hi all

looks like the avr is working as far as i can tell. so that leaves the led board, the photo board and scr assy. all the wiring appears sound. so what's the most likely board that has failed?

thx
 

Birken Vogt

Email NOT Working
Re: kohler 33rz high output part 2

I never read part 1, so I am late to this party, but you test the rotating board by shining light into it and see if it generates. So if that part is working and you have proper voltage to the stationary emitter board, I think that narrows it down.
 

toddbailey

Registered
Re: kohler 33rz high output part 2

this thing is so frustrating. 2 weeks ago I had voltage feeding the led board now I don't. At one point the avr wasn't getting +12 / gnd later on it was.
This project has been a moving target since high out put was discovered.
 

LWB250

Registered
Re: kohler 33rz high output part 2

Troubleshooting a FastResponse alternator is very simple. You've gone about this from all sorts of directions, so I'm guessing you've missed something critical.

1.) No output.

Remove the black plastic cover over the optical coupling (rear of generator where the LED and phototransistor board are located.) Start generator up and shine a flashlight on the phototransistor while watching the meters. If voltage goes to full field, everything from the phototransistor downstream (windings, FR activator) are good. Don't do this for long - just hit it and look for the spike.

If you get nothing when you shine a flashlight on the phototransistor while the generator is running, you've got one of three possibilities:

A.) Bad phototransistor board
B.) Bad FR activator
C.) Bad winding(s)

2.) If the "flashlight test" is good, you're limited to the voltage regulator and LED.

Test the LED out of the circuit with an ohmmeter. Just like any diode, it will conduct in one direction and not the other. You can try viewing it with a camera that doesn't have an IR filter while the generator is running to see if it's "lighting up". You should also be able to read approximately 2 VDC across it while the generator is running and it's being lit.

As for the regulator, about all you can test for is input voltage (B+, or 12VDC) and output to the LED.

The safeguard breaker MUST be closed to get 12VDC to the regulator, so make sure it's closed. Check for continuity across the terminals on the safeguard breaker to make sure they're closing. If not, you can move the leads to another section of the breaker assuming it's good.

These things are dead nuts easy to work on. I did it for decades, from the time they were introduced and later. Follow my checks above and report back what you've found. Unless someone has messed with the wiring or connections what I have posted is pretty much gospel for troubleshooting these units.

Dan
 

toddbailey

Registered
Re: kohler 33rz high output part 2

ok I'm getting a high voltage output of about 175. And no output to the led board. when I do the flashlight test I can hear a whine sound.
Doesn't matter if the avr is plugged in or not or if the cb is open or closed.

I beginning to suspect the avr is bad.
 

LWB250

Registered
Re: kohler 33rz high output part 2

You're not being methodical or clear about this. One thing at a time.

Are you getting a high voltage with the flashlight test, yes or no? If you take the flashlight away does voltage go back down to 0? I don't care about anything else at this point.

Dan
 

Zephyr7

Registered
Re: kohler 33rz high output part 2

If the AVR isn’t putting out any voltage to the LED, then you’d be getting near zero voltage out, not high voltage.

Like Dan said, you need to do this one step at a time, and not try to merge multiple tests together. Do this:

1- remove the black LED housing on the end of the generator. Make sure there is no light shining on the phototransistor that is in the center of the rotating board.
2- start and run the genset. Check the output voltage meters. They should show near Zero. It wouldn’t hurt to have an separate volt meter hooked up to the output here just to have a sanity check against the built-in volt meters. This separate meter should show zero volts (or close to zero volts) too.
3- BRIEFLY shine a flashlight on the phototransistor. Check the volt meters while the flashlight is on. You should see a jump in voltage on the meters, and it should go up above where it would normally be since it should go full field.
4- remove the flashlight, make sure the phototransistor is dark again. The volt meters should drop back down to zero.

If the flashlight test does NOT cause a high voltage reading on the meters, you have a problem with the rotating assembly (phototransistor board, SCRs, or possibly a bad winding). If the flashlight test DOES cause a high voltage reading on the meters, then you have a bad AVR, bad LED, or possibly a problem in the wiring between the two.

If the LED is bad it’s just an infrared LED so easy to replace. Hopefully it won’t be the SCRs, which are a pain to replace, or a bad winding.

First thing to do though is to go through those test steps IN ORDER and ONE AT A TIME and report back the result you get at EACH STEP. Don’t try to jump ahead or summarize what you see because you might miss something that will help us to help you.

Bill
 

toddbailey

Registered
no i'm getting high voltage output, about 175 per leg. Which is why I think it might be more than just one control board.
 

toddbailey

Registered
how dark does the photo board need to be? Pitch black dark? or very dim?

The gen set in under a roof and in a heavly treed area so direct sunlight never reaches it. No problem with using tape over the photo transistor however. btw I do get ac out of the avr going to the led board.

I'll repeat the test as outlined above and report back my findings for each step. thanks all
 

toddbailey

Registered
ok here are the results from each step

1- remove the black LED housing on the end of the generator. Make sure there is no light shining on the phototransistor that is in the center of the rotating board.

used 2 layers electr. tape

2- start and run the genset. Check the output voltage meters. They should show near Zero. It wouldn’t hurt to have an separate volt meter hooked up to the output here just to have a sanity check against the built-in volt meters. This separate meter should show zero volts (or close to zero volts) too.

analog meter reads about 175
dvm reads 179, l1 + l2 360 vac



3- BRIEFLY shine a flashlight on the phototransistor. Check the volt meters while the flashlight is on. You should see a jump in voltage on the meters, and it should go up above where it would normally be since it should go full field.

saw minimal output increase 179 to 189 measured from dvm


4- remove the flashlight, make sure the phototransistor is dark again. The volt meters should drop back down to zero.

returns to 179

If the flashlight test does NOT cause a high voltage reading on the meters, you have a problem with the rotating assembly (phototransistor board, SCRs, or possibly a bad winding). If the flashlight test DOES cause a high voltage reading on the meters, then you have a bad AVR, bad LED, or possibly a problem in the wiring between the two.


saw no difference with or with out tape over photo transistor.
measured 0 vdc and .3 ac on 3b and 5b with out led connected.

13.2 vdc across 1b & 7n

v7-v8 shows continuity

67 -68 shows about 200 kohm


If output voltage is too high will there be any output to the led board?

And according to svc manual looks like its time to check photo and scr boards

since there was a jump in output my guess it's the scr board
 

Zephyr7

Registered
It’s possible the phototransistor board is driving the SCRs on too hard, but my guess is the SCRs are the problem.

I’d wait for Dan’s opinion before you start taking things apart though, he has more experience working on these systems then I do.

Bill
 

pegasuspinto

Registered
replace the rotating SCR heat sink assembly (on the rotor, inside the gen end....NOT fun or easy) and the rotating photoboard on the end of the shaft. (not fun or easy). in theory you can test them and replace one, buuuut.... High voltage with a taped over photoboard means one or both is bad....unless someone might been elbows deep in there and played with the wiring....

Your AVR has nothing to do with the issue.

This is kinda NOT a job for the inexperienced. You could do permanent damage to the generator end if you are careless.
 

LWB250

Registered
If the phototransistor is covered with electrical tape and you're getting any voltage at all other than residual (a few volts AC) either the phototransistor board has failed (not common) or the SCR assembly on the rotor is shorted.

If I was a betting man I would say you have a bad SCR assembly. It can be checked with an ohmmeter when it's disconnected from the phototransistor board to confirm, but you might as well pull it.

Dan
 

Birken Vogt

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The smaller sets were a pain to get into the rotating stuff but this being a 33 kw it might have a large enough frame to get the stuff in and out, anyone remember?
 

toddbailey

Registered
How about we start with the photo transistor board?

2 or 4 bolts and 4 wires to disconnect.
once I get it back to my workstation I can inspect and test individual parts.
1 part in particular looks like it was running hot a 2 watt resistor

With only a few components to test, rebuilding with a few parts or a wholesale remove and replace everything shouldn't be too challenging

but it might be better to replace with a new board.


As far as removing the rear support and getting to the scr assembly that doesn't look like much fun. but I do have the tools to attempt it.

What are the concerns of doing this procedure?
 

toddbailey

Registered
replace the rotating SCR heat sink assembly (on the rotor, inside the gen end....NOT fun or easy) and the rotating photoboard on the end of the shaft. (not fun or easy). in theory you can test them and replace one, buuuut.... High voltage with a taped over photoboard means one or both is bad....unless someone might been elbows deep in there and played with the wiring....

Your AVR has nothing to do with the issue.

This is kinda NOT a job for the inexperienced. You could do permanent damage to the generator end if you are careless.
what kind of damage are you refering to?

fyi I've had this for several years and no issues until just recently.
 

toddbailey

Registered
If the phototransistor is covered with electrical tape and you're getting any voltage at all other than residual (a few volts AC) either the phototransistor board has failed (not common) or the SCR assembly on the rotor is shorted.

If I was a betting man I would say you have a bad SCR assembly. It can be checked with an ohmmeter when it's disconnected from the phototransistor board to confirm, but you might as well pull it.

Dan

If the avr board is ok, why do I not see any out put to the led board?
Any ideas?
 

pegasuspinto

Registered
because the volts are too high. High volts cuts off the LED completely.

You can miswire the set, or potentally loose hardware in the gen end.

you don't need to take the end off. It can be done in place. No fun.
 

Birken Vogt

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The smaller ones I have worked on did need the end bell removed. Would not physically fit past something in there. I don't remember completely but I know it was necessary.
 
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