PRODUCT SUPPORT PROGRAM FOR REPLACING THE 365-9786 EXPUT BOARD ASSEMBLY, 365-9798 DIGIT BOARD ASSEMBLY, AND 365-9803 EXTT BOARD ASSEMBLY ON CERTAIN UPSB505 UNINTERRUPTIBLE POWER SUPPLIES Caterpillar

PRODUCT SUPPORT PROGRAM FOR REPLACING THE 365-9786 EXPUT BOARD ASSEMBLY, 365-9798 DIGIT BOARD ASSEMBLY, AND 365-9803 EXTT BOARD ASSEMBLY ON CERTAIN UPSB505 UNINTERRUPTIBLE POWER SUPPLIES

Usage:

REBE8844-00

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10Dec2012

D-566

O-607

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*Before/After*	PRODUCT SUPPORT PROGRAM FOR REPLACING THE 3659786/">365-9786 EXPUT BOARD ASSEMBLY, 3659798/">365-9798 DIGIT BOARD ASSEMBLY, AND 3659803/">365-9803 EXTT BOARD ASSEMBLY ON CERTAIN UPSB505 UNINTERRUPTIBLE POWER SUPPLIES
4480		PS43786

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NOTE:

This Program must be administered either before or after failure. In either case the decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS43786" as the Part Number and "7755" as the Group Number. If administered before failure, use "56" as the Warranty Claim Description Code and "T" as the SIMS Description code. If administered after failure, use "96" as the Warranty Claim Description Code, and "Z" as the SIMS Description Code.

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NOTE:

The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.

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TERMINATION DATE

31Dec2014

PROBLEM

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The existing EXPUT, DIGIT, and EXTT boards can cause fault propagation and possible contingent damage on certain UPSB505 Uninterruptible Power Supplies in a parallel application with other UPSB505 Uninterruptible Power Supplies.

Existing DIGIT failure.

If an IGBT failure occurs in one UPS, the resultant exchange current can be higher than normal limits and can saturate (disturb) the multiplexers on DIGIT in other parallel UPS. This can generate false alarms such as Inverter Lx fuse blown instant?. As a consequence of this, other inverter(s) could stop and load be transferred to AC bypass.

Existing EXPUT failure.

If a unit fails (UPS or SSC), that unit needs to inform other units it will be disconnected. Otherwise, the system will not work properly (downgraded mode).
The reserve of energy on board may not be sufficient to guarantee this communication in case of failure (example, DC bus short-circuit, power supply failure).

Eisting EXTT failure.

If a UPS fails, it will disconnect whereas higher current can occur in the parallel CTs. At this moment, relays on EXTT board, which are in serial with secondary of CTs may be damaged and contacts may be welded. After that, the installation will not work properly since exchange currents will be false.

AFFECTED PRODUCT

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Model	Identification Number
UPSB505	YTM00100-00124, 126-127

PARTS NEEDED

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Qty	Part Number	Description
1	3659786	BOARD AS. (EXPT)
1	3659798	BOARD AS. (DIGT)
1	3659803	BOARD AS. (EXTT)
In order to allow equitable parts availability to all participating dealers, please limit your initial parts order to not exceed 23% of dealership population. This is an initial order recommendation only, and the ultimate responsibility for ordering the total number of parts needed to satisfy the program lies with the dealer.

ACTION REQUIRED

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This FSB concerns only units in parallel installation and SSC.

Refer to the service manual if/as necessary.

Replace DIGIT & EXPUT & EXTT boards if not at the minimum level requested:
DIGIT NT 07 EJ
EXPUT NT 04 HA
EXTT NT 04 EB

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SERVICE CLAIM ALLOWANCES

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Product smu/age whichever comes first	Caterpillar		Dealer Suggested		Customer Suggested
Product smu/age whichever comes first	Parts %	Labor Hrs%	Parts %	Labor Hrs%	Parts %	Labor Hrs%
0-20000 hrs, 0-60 mo	100.0%	100.0%	0.0%	0.0%	0.0%	0.0%