Thermal Dynamics Pak Master 75XL Plus, Service Manual

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TROUBLESHOOTING 4-10 Manual 0-2747
0.75
VR COM A
A-00307
Anode
Cathode
Forward Bias
Diode Conducting
+
_
Diode Test Symbol
Testing Diode Forward Bias
6. Reverse the meter leads across the diode for reverse
bias testing (refer to following figure). A properly
functioning diode will block in the reverse bias direc-
tion and depending on the meter function will indi-
cate an open or “OL”.
OL
VR COM A
A-00306
Anode
Cathode
Reverse Bias
Diode Not Conducting
+
_
Testing Diode Reverse Bias
7. If a diode checks bad, replace the diode module.
8. Reconnect all cables to proper terminals.
D. Input PC Board Test
Check Input PC Board for shorted input diode.
Input PC Board
Solder Side of PC Board
A-02563
Remove AC power and with an ohmmeter set on the di-
ode range make the following checks:
M e t e r (+ ) M e t e r (-) I n d ica t io n
A C 1 (-) O p e n
A C 2 (-) O p e n
A C 3 (-) O p e n
(-) A C 1 D io d e D ro p
(-) A C 2 D io d e D ro p
(-) A C 3 D io d e D ro p
(+ ) A C 1 O p e n
(+ ) A C 2 O p e n
(+ ) A C 3 O p e n
A C 1 (+ ) D io d e D ro p
A C 2 (+ ) D io d e D ro p
A C 3 (+ ) D io d e D ro p
The meter should indicate a diode drop in one direction
and an open in the other direction for each check.