Page 28 MFA 4p – INSTRUCTION MANUAL 7ML19985FM01
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Troubleshootiing
Troubleshooting
Notes:
• Voltage levels are dc, nominal values, and may appear to be pulsing, coincidental
with LED 1.
• If diagnosis does not solve the malfunction, the probe, pre-amp or MFA 4p may be
defective.
• If no spare circuit boards or probes are available for interchanging, the MFA 4p may
be tested as follows in order to determine which section is defective:
a. To find out if the MFA 4p is defective:
i. Disconnect the pre-amp.
ii. Set ppm switch SW2 to X 1 position and turn potentiometer to 15.
iii. Connect one Iead of a 530 ohm, 1 watt resistor to terminal 7 and then
momentarily contact terminal 8 at a rate of once per second. If the MFA 4p is
functional, the relays will energize after two puIses and de-energize
approximately 8 seconds after last pulse.
b.To find out if the RMA is defective:
i. Disconnect pre-amp from the MFA 4p. Attach probe across terminals
TB1 1/2 and a 24V DC(floating) power supply across terminals TB2 3/2,
according to the RMA Interconnectiondiagram on page 8.
ii. Run equipment to be monitored at normal operating speed or pass a ferrous
object in front of and as close to probe as possible at a continuous rate.
iii. With an oscilloscope, look for approximately 6V peak to peak pulses or
alternating hi/lo levels across ground and link 3. Or with an amp meter
connected in series between the RMA and the 24V DC power supply, Iook
for hi/lo levels of approximately 12mA/40mA alternating at the rate of the
passing ferrous objects.
LED
1
LED
2
term 7/8
(note 1)
C8
term 1/2
relay 1 out
term 4/5
relay 2 out
normal pulsing on 24 V 27 V closed closed
alarm pulsing off 24 V 27 V open open
probe reversed
polarity
on off 20 V 27 V open open
probe wiring
open circuit
off off 27 V 27 V open open
probe wiring
short circuit
off off 0 V 27 V open open
relay defective pulsing on 24 V 27 V open open
7ML19985FM01.book Page 28 Wednesday, May 21, 2008 2:17 PM
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