FG00064 R01
PARTS-SERVICE
October 20, 1997
GRAM E30-50FR
Subject: Amplifier Failures
Premature traction amplifier failure may occur in the field.
The following conditions can lead to these premature failures:
1. Improper brake adjustment causing dragging of one or both traction motors.
2. Improper steer potentiometer adjustment causing the truck s software to think truck is in a turn.
3. Using a battery with one or more dead cells.
Any of the above may lead to an imbalance in the traction system causing one or both motors to be over-
loaded, resulting in excessive power draw.
An amplifier failure is due to heat build-up of the amplifier module. This amplifier heat build-up is caused by
motor overload whereby the motor overload is caused by one or more of the above noted causes. While the
system is designed to handle excessive heat, several integrated circuits in the amplifier are found to be of
commercial grade (0°C to 70°C.) rather than industrial grade (-40°C to 85°-100°C). When the integrated
circuits temperature rating is exceeded, it does not perform as expected, thus resulting in the amplifier failure.
The amplifier s operating temperature range is designed for operations between -40°C to +85°C.
Further, in order to avoid amplifier failure as described herein, we have added software designed to look
specifically at motor and/or amplifier temperature imbalances. A motor and/or amplifier temperature imbal-
ance will result in a shutdown and error message as follows:
" Left/right traction motor temperature imbalance (Error Code 83)
" Left/right traction control temperature imbalance (Error Code 84)
...continued
We reserve the right to make changes in design or add improvements without incur-
ring the obligation to make such changes in equipment previously manufactured.
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If the lift or traction system shuts down, and an amplifier is believed to be defective, perform the following
checks:
1. Verify all fuses are in good condition.
2. Check unit for in-line fuse configuration. Refer to Parts-Service Gram FG00066. Modify the wiring if
necessary.
3. Check power cables for open circuits or loose connections.
4. Inspect motor terminals for tightness. Refer to Parts-Service Gram AG00011 for the drive motor.
5. Go into diagnostic output tests 17 (for a suspect LH amplifier), 18 (for a suspect RH amplifier) and 19
(for a suspect Lift amplifier). If motor movement is detected, the amplifier is probably not defective.
6. Check the resistance between battery positive and the chassis and between battery negative and the
chassis. The resistance should be greater than 20 megaohms. If less than 20 megaohms, isolate the
suspect amplifier and recheck the resistance. If the resistance checks okay with the amplifier isolated,
the amplifier is probably defective. Refer to Parts-Service Gram FF00048.
7. Check the resistance between the system controller and the chassis. The resistance should be greater
than 20 megaohms. If not, refer to Parts-Service Gram FG00067 for the proper procedure for isolating
the system controller.
If it becomes necessary to change an amplifier, for any reason, each of the following checks must be per-
formed prior to powering up the unit.
1. Inspect the drive motor terminals for tightness (traction amp only). Refer to Parts-Service Gram AG00011.
2. Measure the resistance of the drive motor field windings at cables F1 and F2 at each traction amplifier
(traction amp only). If the resistance measures greater that 1.5 ohms or less than .9 ohms, disconnect the
field cables from the motor terminals and measure across the terminals. If the reading is still out of range,
contact Hyster Service.
3. Verify software the software version is greater than 2.02, if not contact Hyster Service.
4. Verify unit does not have in-line fuse configuration. Refer to Parts-Service Gram FG00066.
5. Verify the encoder pulley is secure on the encoder shaft (traction amp only). Refer to Parts-Service
Gram FG00061.
6. Verify the encoder drive pulley is secure on the motor shaft (traction amp only). Refer to Parts-Service
Gram FG00061.
7. Inspect diodes for opens or shorts. Refer to the Parts-Service Gram FF00046.
8. Verify the static strap is intact and in good condition.
9. Verify the steer pot is tight in the flexible connector (traction amp only). Refer to Parts-Service Gram
F600062.
10. Verify the steer pot is properly adjusted (traction amp only). Refer to the Service Manual.
...continued
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9. Verify the steer pot is tight in the flexible connector (traction amp only). Refer to Parts-Service Gram
FG00062.
10. Verify the steer pot is properly adjusted (traction amp only). Refer to the Service Manual.
11. Check the resistance between battery positive and the chassis and between battery negative and the
chassis. The resistance should be greater than 20 megaohms. If less than 20 megaohms. Refer to Parts-
Service Gram FF00048.
12. Check the resistance between the system controller and the chassis. The resistance should be greater
than 20 megaohms. If not, refer to Parts-Service Gram FG00067 for the proper procedure for isolating
the system controller.
13. Check the brakes for proper clearance and drag (traction amp only). Refer to Parts-Service Gram
HB00015.
14. Ensure the battery is charged and tested.
If the above checks okay, and a traction amp is being changed, go into diagnostics output tests 17 or 18 (which
ever applies), and check for motor gear box noise and resistance.