Thermal Dynamics PAK Master 150XL, Руководство по обслуживанию

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Manual 0-2728 4-17 SERVICE TROUBLESHOOTING
2. FET/Heatsink Output Diode Checks
Remove input power from the unit.
Isolate each FET/Heatsink Assembly by removing the
red wire #12 at E18 and the black wire #11 at E17 on
each FET/Heatsink Assembly. With an ohmmeter set
on the diode range, check between the two output
studs, E17 (- output) to E18 (+ output). This should
indicate a diode drop in one direction and open in
the other.
If the checks indicate shorted or open in both direc-
tions then the upper or lower pair of FET/Heatsink
Assemblies should be replaced.
3. MOSFET Resistance Checks
The Power Supply contains four identical FET/Heat-
sink Assemblies. On each assembly there are two
MOSFET devices that must be checked. Use an ohm-
meter to check for the proper resistance of the
MOSFET's as follows:
a. Locate Q1 and Q6 on the FET/Heatsink Assem-
bly.
A-01414
Q1
FET/Heatsink and
Capacitor PC Board
Assembly
Q6
b. Place the meter (+) lead on gate lead of Q1 and
meter (-) lead on source lead of Q1. The meter
should indicate approximately 2.5K ohms.
A-00553
MOSFET
Spring
Clip
Gate
Drain
Source
c. Place the meter (+) lead on drain lead of Q1 and
meter (-) lead on source lead of Q1. The meter
should indicate >100K ohms.
NOTES
Make measurements near the body of each
MOSFET.
Be sure that the meter lead probes penetrate the
protective coating on the MOSFET.
d. Place the meter (+) lead on drain lead of Q1 and
meter (-) lead to the heatsink. The meter should
indicate >1 meg ohms.
e. Place the meter (+) lead on gate lead of Q6 and
meter (-) lead on source lead of Q6. The meter
should indicate approximately 2.5K ohms.
f. Place the meter (+) lead on drain lead of Q6 and
meter (-) lead on source lead of Q6. The meter
should indicate >100K ohms.
4. FET Reset Diode Check
Use an ohmmeter set to the diode function and check
the reset diode as follows:
a. Place the meter (+) lead on E14 and the meter (-)
lead on E12 of the FET/Heatsink Assembly Ca-
pacitor PC Board to check the reset diode. The
meter should indicate between 0.4 to 0.6 volts us-
ing the diode function.
b. Reverse the meter leads and the indication should
be a capacitor charging.
c. Place the meter (-) lead on E14 and the meter (+)
lead on E13 of the FET/Heatsink Assembly Ca-
pacitor PC Board to check the reset diode. The
meter should indicate between 0.4 to 0.6 volts us-
ing the diode function.
d. Reverse the meter leads and the indication should
be a capacitor charging.
If the indication is a short, then replace tupper or
lower pair of FET/Heatsink Assemblies.