# Powermate/Black Max GX390 high voltage and idle solenoid



## Johnny Frugal (Jul 27, 2020)

Greetings all,
I just acquired this generator. Starts on the first pull, engine runs great. However, the no load voltage is approx 140v per leg (270-280 hot-hot). 125-130v with no load I would understand. Also, it seems to be equipped with an idle control solenoid, with it's leads cut off. This model didn't offer auto idle control, is it possible they just lopped off the cable at the factory and left the solenoid there? Any suggestions on where to start chasing the high voltage problem? I've found an original user manual, which tells almost nothing, and a gx390 manual.


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## iowagold (Jan 22, 2020)

load it up with a hair dryer or a space heater set to 1200-1500 watts
and look at the voltage. should be 120 -125 vacat the 1500 watts.

yea this is what i do not like on the standard gen systems..
I prefer the inverter gen units that hold the voltage over the full load range of current.
the honda eu series is the best in class..
but you pay more for them.
and yes they hold value for resale too!


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## Johnny Frugal (Jul 27, 2020)

Here's what I did in case it helps anyone else. Using only the governor tension screw, I adjusted with no load until I got 60hz AC output (my mutimeter has a frequency counter). At that point the no load voltage was about 129V. Much better than the 140V previously. Then, I used a space heater on one leg, and heat gun on the other, as my dummy loads. This dropped frequency down to about 58Hz, and Voltage to about 107V. Again using only the governor tension screw, I adjusted until the output frequency reached 60HZ. This seemed to hold within about +/- 0.2Hz. At that point the output voltage measured 125V. I couldn't be happier. This generator is older, but I got it with zero hours on it. An older gentleman had purchased it, put oil in, but never even a drop of gas. I paid less than the cost of a new GX390 engine. Not as fancy as a new inverter genset, but good enough for me for the moment. I do believe that they must have bought the engines from Honda with the auto throttle servo already installed, then just cut the lead off on the models that didn't use it. I'm not the only one who's mentioned this online. Hope this helps someone else down the road.


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## iowagold (Jan 22, 2020)

you can always do a line conditioner for the sensitive equipment.
they have those for bands and music pa gear.
firman makes a good unit.
and many other brands are out there.
see
sweetwater.
click here for sweetwater
tell them iowagold sent you!
I know chuck. they are a great bunch of guys!


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## Johnny Frugal (Jul 27, 2020)

LOL, I've bought more than a bit of gear from Sweetwater over the years. Alas, with my pandemic budget, Chuck's gonna have to live without any more of my money for a bit.


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## iowagold (Jan 22, 2020)

small world!
yea I have a music studio and do voice over as well.
yea i have a few more things I want after things get a bit better as well.
till the stuff hit...
i was wanting to go to sweet water gear fest 2020..
you make some great connections at events like that!
the after parties and mixers...


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## eaw1977 (Oct 14, 2021)

Johnny Frugal said:


> Greetings all,
> I just acquired this generator. Starts on the first pull, engine runs great. However, the no load voltage is approx 140v per leg (270-280 hot-hot). 125-130v with no load I would understand. Also, it seems to be equipped with an idle control solenoid, with it's leads cut off. This model didn't offer auto idle control, is it possible they just lopped off the cable at the factory and left the solenoid there? Any suggestions on where to start chasing the high voltage problem? I've found an original user manual, which tells almost nothing, and a gx390 manual.
> View attachment 7978
> View attachment 7979
> View attachment 7980


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## eaw1977 (Oct 14, 2021)

I have the exact same generator....but mine has NO throttle lever and wants to run wide open....any ideas???


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## LaSwamp (Mar 16, 2021)

iowagold said:


> you can always do a line conditioner for the sensitive equipment.
> they have those for bands and music pa gear.
> firman makes a good unit.
> and many other brands are out there.
> ...


Wow, you know guys from Sweetwater? That's cool. 

I have been looking for a graphic EQ, the one with the florescent spectrum analyzer like we had in the 1980s, but they seem as rare as hen's teeth these days.


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## drmerdp (Apr 10, 2018)

eaw1977 said:


> I have the exact same generator....but mine has NO throttle lever and wants to run wide open....any ideas???


Generators don’t have throttle levers. Sometimes conventional generators have Idle switches. It’s more of a gimmick then a useful feature.


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## iowagold (Jan 22, 2020)

eaw1977 said:


> I have the exact same generator....but mine has NO throttle lever and wants to run wide open....any ideas???


do you have a tach?
we need to know the rpm.
most standard portable non inverter gens need to run at 3600 rpm to get the 60 hz.
a tach or tach with an hour meter is a great idea to add on to any gen set!


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## eaw1977 (Oct 14, 2021)

eaw1977 said:


> I have the exact same generator....but mine has NO throttle lever and wants to run wide open....any ideas???


got it fixed...govenor was out of adjustment


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## iowagold (Jan 22, 2020)

! there ya go!
yea gov needs to be spot on to work right.
make sure to test with 100 watt load and 5000 watt load.
you should have 60 hz at around 3000 watts.
and at 300 watts maybe 61.5 hz
and at 5000 watts 59 hz.
depending on the carb jets.
and how close you have the gov set to spot on.


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