Subzero Wolf MD24, Service Manual

Page 27

MD24 and MD30 

Troubleshooting Guide

5-4

#824820 - Revision A - December, 2013

CONTROL PANEL ASSEMBLY TEST:

Control panel consists of a Piezo Control Panel. Control Panel keyboard consist
of two parts; a left side keyboard that communicates only into right side keyboard
through keyboard connection cable. Right side key board communicates with
PSU-Drawer board through Display Harness. Key operation is only occurring
between Right side key unit and PSU-Drawer board in backside of oven.  Display
text and buzzer sound is occurring between CPU-Drawer board and PSU-Drawer
board and this data is fed through right side of Control Panel Assembly.

Note: 

CPU-Drawer board and CPU-Drawer harness do not affect key operation.

Before Testing:

1. Disconnect power supply cord, and then disassemble as per Section 4

Component Access starting on Page 4-4.

2. Open drawer and block it open.
3. Discharge high voltage capacitor. 
4. Disconnect leads to primary side of the MD Transformer.
5. Ensure that these leads remain isolated from other components and oven

chassis by using insulation tape.

A few keys not operating on Control Panel Assembly:

1. Replace Control Panel Assembly.

Left side only keys not operating:

1. Reseat keyboard connection cable between Left and Right keyboards. Reseat

Display Harness between right side keyboard and PSU-Drawer board.

2. Replace Control Panel Assembly.
3. Replace PSU-Drawer board.

No Keys are operating:

1. Check for breaks on Display Harness.
2. Replace Control Panel Assembly.
3. Replace PSU-Drawer board.

COMPONENT TEST

TEST PROCEDURES

Note:

Pictures of the four main boards are at the end of this section.

PROCEDURE LETTER

A

CPU-DRAWER BOARD & DISPLAY HARNESS TEST:

1. Disconnect power supply cord, then remove outer case.
2. Open drawer and block it open.
3. Discharge high voltage capacitor.

No LED back lighting on CPU-Drawer board - but operates correctly.

1. Check for breaks on Display Harness and CPU-Drawer board harness to

main harness.

2. Replace CPU-Drawer board.
3. Replace Display Harness.
4. Replace PSU-Drawer board.

No Display but operates correctly.

1. Reseat CPU-Drawer board harness and Display Harness.
2. Replace CPU-Drawer board.
3. Replace Display Harness.
4. Replace PSU-Drawer board.

No Sound but operates correctly.

1. Check users has not disabled sound.
2. Reseat Display Harness and CPU-Drawer Board harness.
3. Replace CPU-Drawer board.
4. Replace Display harness.
5. Replace PSU-Drawer board.

B