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Boom Truck Blues for Your Amusement


rockmeupto125

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As for which wire is which, it doesn't make sense to me so I won't speculate.  The 145v instead of 120 is probably just because the RPM is too high.

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5 minutes ago, XXitanium said:

Bad regulator? Should it be 120V and 240V?

 

https://gentekpower.com/forums/viewtopic.php?t=133

 

Pretty sure there's no regulator, the voltage is RPM dependent.  240 would come from using the two 120 hots....or cranking the RPM up to 3600 😵

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Modern fancy generators might not use the old school mechanical governor.  If they use electronicals to see the voltage and regulate the RPM based on voltage instead of actual RPM then I guess it could be called a regulator.

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39 minutes ago, superhawk996 said:

Pretty sure there's no regulator, the voltage is RPM dependent.  240 would come from using the two 120 hots....or cranking the RPM up to 3600 😵

Part of what I was wondering, no voltage regulator?...is the unit running at the correct RPM?

20210427_230004.jpg

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In playing with the throttle on generators I've seen 40 to well over 150v.

 

Governors aren't perfect, but you can usually dial them in to keep within a good voltage range.  The one on my Onan was a little off so I tweaked it.  From memory there were 3 different things to adjust to get the voltage right at low, medium, and high load.  The governor relies on a bunch of stuff, but in my mind the spring is what makes it less than perfect, there's just no way to not have some amount of rising resistance as the spring is stretched.  I think I got mine down to around 4-5v. of variation, more than good enough.

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8 hours ago, superhawk996 said:

Very odd since the engine is making no electricity for the vehicle/boom to use.  Does the battery jumper switch have to be on for the engine to run?  If so, did you try the emergency bypass with that switch on?

 

If the panel is truly only operational with the engine running that means it's sharing power with the generator stuff, like the fuel pump & ignition, which seems totally wrong.  Or maybe that switch isn't activating the emergency bypass solenoid and instead is activating the normal down solenoid which might require hydraulic pressure.  Either way, it would be easy to swap the panel feed from the generator controlled circuit to a battery line so that the emergency down will work with a dead engine.

 

 

I had fixed the problem with the supply voltage on the aux battery line.  Now the unit starts and runs without the jumper switch

 

Today I hope to test the isolator and see if the diode function is actually working.

 

There are two safety switches at the bucket.  One actuates the solenoid to open the hydraulic and drop the bucket as mentioned.  The other actuates the "battery jumper" solenoid just like the one on under the dash.  So if all is working well, if the aux battery has decreased power and won't start the Onan, from the bucket one can actuate the battery jumper solenoid and use both batteries to start the hydraulic.

 

I suspect there's some wizardry in place so that there is only power to the Onan and the hydraulic controls when the engine is running.  Once you push the start switch, everything stays on until the motor stops. I know the fuel pump does not run constantly. 

 

I'll disconnect the battery with the engine running.  That should be conclusive as to whether the Onan makes its own juice or not. 

 

When crossing the wires I did not think to extend the range of the VOM. I'm stuck in an analog world thinking the "gauge/LCD" would just peg.  I need to recheck them on the 660 VAC scale. The "no load" voltage rating is 132.  One day my HF VOM (remember the free ones?) read 140, the next day my Klein read 144-145. Not THAT far off.

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2 hours ago, rockmeupto125 said:

There are two safety switches at the bucket.  One actuates the solenoid to open the hydraulic and drop the bucket as mentioned.  The other actuates the "battery jumper" solenoid just like the one on under the dash.  So if all is working well, if the aux battery has decreased power and won't start the Onan, from the bucket one can actuate the battery jumper solenoid and use both batteries to start the hydraulic.

That makes sense, I wondered why it wouldn't have the jumper control.  The emergency down might work if you hit the jumper, or some other momentary switch.  Some 'emergency' controls are wired so that you have to hit two things, I guess it's a safety against accidentally actuating the 'emergency' circuit.  But if all's working well you *shouldn't* ever need the emergency down.  At least some stuff is looking better than it seemed.

 

Having two pairs that give AC power makes me think the mystery is solved, but it's odd to me that one pair has continuity to ground and the other doesn't, that's why I was hesitant to say much about that part.  It seems to me that if an AC hot wire has continuity to ground it would energize the chassis when the generator's running.  Or, maybe it's a feedback through the brushes and if the engine were rotated a bit the other pair may have done the same...something to test on your next probing adventure perhaps.  Luckily you have the pulley that'll hopefully let you roll the engine by hand.

 

I think most meters have some kind of indicator to let you know the voltage is out of range so it'll spur you into changing the range, sometimes it's not obvious.

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it was tense trying to keep all the jumpers away from ground with the motor vibrating, then trying to clamp them to the meter probes while maintaining some isolation.  I'll try to do a better job today.

 

Those continuous to ground show a little bit of resistance, not much.

 

The emergency down does not work if the emergency battery solenoid switch is activated.

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5 minutes ago, rockmeupto125 said:

The emergency down does not work if the emergency battery solenoid switch is activated.

Even without enough juice to crank, I think it'll probably work in conjunction with holding the start button/switch since that energizes the other generator circuits (and probably the bucket controls) just as if it were running.

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If the motor is running too fast, then the frequency should be off also.  Do any of your meters have a frequency or RPM counter?  Both are common in modern automotive type VOMs, not so much on electronics/hobby type meters.  Often the frequency mode is just marked "Hz" which may be obvious, but want to be sure.

 

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Since you lose Boom control voltage when the engine stops. I am going to take a guess that the DC Boom control voltage is fed from K3 relay (Engine Run relay) opens on engine shutdown. 

Edited by CALCXX
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