Tweco PAK 10 - Manual (Page 36)

Service 24 Manual No. 0-0515
Q. The best way to check the printed circuit control
card is to replace it with one known to be good. The
same card is used in the PAK 10, 22, 44 and 350.
R. Watch the high frequency points during a cut. If
the high frequency remains on, check the resistance
of the toroid coil (See test G) and of the relay CSR.
The coil of relay CSR should read about 3K ohms
measured from pin A to pin B (bottom view same
as time delay - See test C).
S. The remote control jack has a switch and a 10,000
ohm resistor which is switched out of the circuit
when the remote control potentiometer is plugged
in. Performing Test O checks that this resistor is
properly connected.
T. Remove the printed circuit card from the machine
and check for continuity from the 1st and 6th pins
on the receptacle (counting as in O above). If there
is no continuity, the shunt is not properly connected.
U. With a soldering pencil, disconnect the “pigtail” lead
to the SCR’s one at a time. When more than one
wire is connected to the pigtail, the two wires should
be connected to each other. Operate the unit with
one and then the other SCR disconnected and note
the maximum amperage. The output will remain
unchanged when the bad SCR is disconnected and
will drop to minimum when the good SCR is dis-
connected.
V. A bad varistor (VR) is difficult to detect by itself. It
will, however, cause the D8 diode on the control
bridge to short and burn out. If this happens, or if
the varistor looks burnt, replace both.
This concludes the test procedures.