I've been troubleshooting electronics since 1970. It's rare for the
problem to be other than a bad connection.
At the Fort Monmouth Army school the instructors heated and removed an
end cap from glass tube fuses and inserted too-short heavy bus wire or
paper tags with "good fuse" on them, to teach us to check the power
first, and test fuses with an ohmmeter.
On Thursday, August 1, 2019 at 3:07:38 PM UTC-4, Jim Wilkins wrote:
Grin... Well someone else here found the problem and 'assumed' a bad cap.
after a day I was brought it to help... I sorta bought into to the 'bad cap'
I've been thinking of some sort of trouble shooting guide for people.
It seems like a common mistake is assuming the problem is the first thing
you think of. And then you follow that idea down some rabbit hole.
The first thing to do when trouble shooting is to think of all the
things it could be. Make a list if you have to. Then start by checking all the
simple things on the list. (simple as in simple to test.)
Hmm, well and get lots of data on the problem, that's important. I do trouble
shooting on the phone/ email every week or two... you learn to ask a lot of
On Thu, 1 Aug 2019 13:33:43 -0700 (PDT), email@example.com wrote:
But oftentimes the bad cap is the culprit. I live on an island that is
mostly rural or semi-rural so we have lots of water wells. And nearly
every well has a single phase cap start motor that spins the pump. My
neighbor's well has a second pump that is used to pump and pressurize
the water for his house because it is quite uphill from the well head
and his well is already pretty deep. The motor refused to start and
did the typical humming till the breaker pops business. So I told my
neighbor to just go buy a start cap. Even though we are mostly rural
there is a naval base on the north end and a Home Depot. But nobody
had a start cap for his well. Not even the well pump installers. All
they could do was order the cap. So I took one out of my band saw
which got him water and he ordered two caps so he would have a spare.
When a student asked if there was a troubleshooting procedure the
answer was yes, but since it covered every possibility it took far too
long to run through. They said they'd found that teaching students how
the circuits operated in detail resulted in much shorter downtimes of
the communications links we supported.
That worked for them as long as the Vietnam draft brought in science
and engineering grads with the aptitude and (more importantly) the
patience to learn complex systems. After it ended they had to
downgrade to board-swapping.
Ah, well, the running backwards strongly indicates it is running on
single phase. Check the power switch/motor starter to make sure all 3
phases are connecting. Check any fuses. Look for loose/broken wires.
Without knowing what sort of switch/motor starter it has, I can't get
more detailed. It COULD be the motor, but could as likely be something
Certainly the start capacitor. I don't know whether that one
has a run cap at all, but starting sometimes backwards says that it is
the start cap.
Any clue as to which model? There seem to be a number of
I downloaded the manuals for the 4V, and it shows as having a
3-phase motor, so no start cap.
But if it is a single-phase motor, it should have a start cap,
and it will likely be under a bulge cover screwed to the side of the
motor. Unscrew the cover (with the saw disconnected from power) and
pull the quick-disconnect (push-on) connectors from the cap, unscrew the
clamp which holds it, and pull it out. Read the voltage and capacitance
(uF) from what is printed on the cap, and go to a motor place to
purchase an equivalent. When you put the new one in -- just make sure
that one push-on goes to one terminal and the other to the other.
(Likely there are two or three push-on tabs for each terminal, and if
you push both onto the same terminal you will probably stall the motor.
Which wire goes to which terminal should not matter, as this is an AC
application, not DC -- which electrolytic capacitors do care about.)
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