42 • Service Manual — COATS Models 950/950 ProRacer/1025/1050/1055
Direct Drive
PCB Checklist Addendum
Hennessy has noticed a considerable increase in the
amount of NAD’s (No Apparent Defect) for the
950/1050 PCB’s (8111886). Most NAD’s are in the
“Chasing Weights” category. The next reason for PCB
return is due to the Motor Controllers failing. Some of
the PCB’s returned tested OK. Below is a quick test to
help determine if the PCB is defective. This test does
not pertain to any other PCB’s.
Remove PCB from Touch Panel.
Tools Needed:
Digital Multimeter with leads.
Diode Test
Using a multimeter, set the function indicator to the
diode function and check Diodes D9 (Rev D boards) and
D10/D11 (Rev E and above) to see if they are shorted.
Perform the following procedure for each diode.
1.
Connect the multimeter’s black lead to the left side
of the diode and the red end on the right. If the diode
is good, you will hear a short beep and the reading on
the meter should be between .5 and .7, (if you’re using
an Ohmmeter the reading will be about 5 Meg Ohms
(
Ω
)). If the diode is bad, you will hear a continuous tone
and the multimeter reading will be 0 (same for ohm
scale) unless it’s open - no tone reading.
2.
Next, switch the multimeter leads. Connect the
black lead to the right side of the diode and the red lead
to the left. In this configuration, your multimeter should
read an open (OL), if the diode is good (same for
Ohmmeter). The multimeter display should look the
same as it does when the leads aren’t connected to
anything. If the diode does not read open, in this step,
then it is bad.
IC Test
Use a multimeter to check for ground shorts on IC’s
(U8, U12, and U19).
1.
Set the multimeter up for continuity (or diode)
checking.
2.
Connect the common lead of the multimeter to a
ground point on the PCB. A good place is the negative
end of capacitor C15 or C16 (see fig.1).
3.
Take the multimeter positive lead and check the
pins on the IC’s above.
Note:
•
Pin 7 is GND
on the IC’s. (You will hear a continu-
ous beep).
•
Pin 14 is VCC
on the IC's. (You will hear a short beep
or read .5 - .7 on the Diode Scale.) This is OK. Only if
you measure 0 Ohms or hear a continuous beep is the
IC bad.
•
IC U19, pins 7, 11, 14, and 13
are the only pins
where you should read 0 Ohms or hear a continuous
beep.
If any other pins (not listed) are shorted to ground,
read 0 Ohms, or you hear a continuous beep on the
IC’s listed above, THE PCB IS DEFECTIVE. DO NOT
INSTALL PCB BACK INTO THE BALANCER.
If the IC’s and the diodes check out OK, but the PCB
does not display any lights, THE PCB IS DEFECTIVE.
DO NOT INSTALL PCB BACK INTO THE BALANCER.
Rev 1
Figure 1 - PCB 8111886
Figure 2 - Pin Configuration
Pin 1
Pin 7
Pin 8
Pin 14
