Product Support Bulletin 779

PRODUCT SERVICE BULLETIN LAND MOBILE PRODUCT SECTOR RADIO NETWORK SOLUTIONS GROUP PSB # 779 1301 E. ALGONQUIN RD. APC # 448,482,509 SCHAUMBURG, IL. 60196 Date: SEPTEMBER, 1996 (847)576-0180 EXPIRES : 9/30/97 Subject: QUANTAR STATIONS WITH INTERNAL HIGH STABILITY OSCILLATORS FAILING DIAGNOSTICS AND LOSING REFERENCE. MODELS AFFECTED: T5365A WITH X873__ UHSO OPTION MODULES AFFECTED: TTN5070A & B SYSTEMS AFFECTED: BOTH CONVENTIONAL AND TRUNKING PROBLEM DESCRIPTION: The OP-AMP (U301) which buffers the 8 volt oven reference voltage oscillates, which causes the 5MHZ reference oscillator to become inoperative, thus shutting the station down. NOTE: Even if the station is presently working; it is recommended that this change be made to eliminate the potential of any OP-AMP instability. PROBLEM RESOLUTION: To eliminate this problem, change R305 from the 11.0Kohm value to a zero-ohm resistor (Motorola part number 06-11079A01). NOTE: All stations shipped after April 8,1996 contain this change. Resistor can be obtained at no charge from the Americas Parts Division by making reference to this bulletin. Authorized Motorola Service Shops (MSS's) will be allowed 15 minutes labor, plus travel time to the site to make this resistor change.