Firepower FP-18, Service Manual

Service Manual 0-2692

11

Firepower FP-18 Plasma Cutter

7 .  Faulty Control PCB  or Relay

CAUTION

 Be sure torch is directed away from people or haz-
ards. A pilot arc may start!

a.  Push the test button on the side of the Relay. If

the Compressor starts and the torch operates,
the PCB or Relay has most likely failed.

The PCB  can be isolated by removing the push
on connectors from the Relay coil and measur-
ing the relay coil with an ohmmeter. If the coil
measures between 50 - 100ohms, the Relay is
good and the PCB should be replaced.

If the Compressor runs intermittently and arc-
ing can be seen in the Relay case while the torch
switch is held on, the relay contacts are worn
and the Relay should be replaced.

F.  Power OK, fan runs, compressor runs

intermittently, Relay Case shows
arcing when the torch switch is held
on.

1.  Faulty Relay.

a.  If the Compressor runs intermittently and arc-

ing can be seen in the Relay Case while the torch
switch is held on, the relay contacts are worn
and the Relay should be replaced.

G.  Power OK, fan runs, compressor starts

then shuts down as soon as the torch
switch is pressed.

1.  Shorted, damaged, or incorrect torch parts.

a.  Check that all torch parts are in good condition

and designed for use in the PCH-10 torch.

2.  Faulty (open) Voltage Divider Resistor.

a.  The voltage divider is the top Resistor.  Discon-

nect the push-on connectors and measure the
Resistor with an ohmmeter. It should read 1K
ohms.  If measurement is not 1K ohms, replace
Resistor.

3.  Shorted Bridge Rectifier (BR1).

a.  Probable if a loud hum or buzz is heard from

the main transformer after the Relay actuates.

If hum or buzzing noise exists, replace Bridge
Rectifier. (replace lower Bridge Rectifier, clos-
est to Chassis).

H.  Power OK, fan runs, compressor runs,

no pilot or cutting arc with the torch
switch pressed.

1.  Worn, contaminated, or incorrect torch parts.

a.  Check that all torch parts are in good condition

and designed for use in the PCH-10 torch.  Re-
place worn parts as necessary.

2.  Parts not assembled correctly.

a.  Reassemble torch parts.

3.  Damaged torch or leads.

a.  Check per subsection 3.6, Torch and Leads

Troubleshooting.

4.  Faulty Control PCB.

a.  Listen for a faint, sharp clicking noise, at about

3-4 clicks/second from the Ferrite Core Assem-
bly.  If nothing is heard, the PCB should be re-
placed.

5.  Faulty (open) Pilot Resistor.

a.  The Pilot Resistor is mounted closest to the chas-

sis. Disconnect the the push on connectors and
measure the resistor with an ohmmeter.  It
should read 0.5 ohms (essentially a short).

6.  AC input too low.

a.  If the AC line is below about 105vac, the torch

may not always start.  Try an outlet on a differ-
ent branch circuit.

7.  Faulty Ferrite/Transformer Assembly.

a.  The Ferrite Transformer Assembly is used to

generate a high voltage pulse to establish the
pilot arc. Troubleshooting is limited to visual
inspection. The two primary connections and
two secondary connections should be checked
for general integrity and snug fit onto the push
on connectors.  The Transformer Assembly it-
self should be free of large ferrite chips and
cracks along the core.

I.  Torch pilots but does not cut well.

1.  AC input power too low.

a.  Use shortest service from AC outlet to breaker

panel as possible or larger gauge extension cord.

2.  Work cable not attached.

a.  Check work cable connection.

3.  Restricted air flow.

a.  Check lead for kinks or pinching restricting air

flow.