SERVICE AND REPAIR NOTES 
Bulletin
TECHNICAL INFORMATION / 8000 W. SUNRISE BLVD. / FT. LAUDERDALE, FL 33322



SRN- 1303 
APC 672, 749 
Date: April, 2000

Memo To: SRN Mailing List Deadline: December 31, 2000 

From: PPP Subscriber Product Group / CGISS

Subject: HT750/HT1250 Turn On in Charger (with ON/OFF switch in OFF position) 

Symptoms: 
The user may experience the following when charging a Nickel Cadmium Battery while attached to an HT750/HT1250 radio (UHF/VHF) in its associated Motorola charger.
After the battery has reached full charge, and the charger green light is constant, if the radio and battery are left in the charger, the radio may momentarily turn on every few minutes. The radio may emit a beep or beeps and turn back off. 

Potential Problem Radios:
Models Affected: AAH25KDC9AA2AN, AAH25KDC9AA3AN, AAH25KDG9AA4AN, AAH25RDC9AA2AN, AAH25RDC9AA3AN, AAH25RDG9AA4AN, AAH25SDC9AA2AN, AAH25SDC9AA3AN, AAH25SDG9AA4AN
AAH25KDF9AA5AN, AAH25KDH9AA6AN, AAH25RDF9AA5AN, AAH25RDH9AA6AN, AAH25SDF9AA5AN, AAH25SDH9AA6AN, AAH25RDH9DU5AN, AAH25RDH9DU6AN, AAH25SDH9DU5AN, AAH25SDH9DU6AN

Serial Numbers: 672TYSxxxx through 672TAFxxxx
749TYSxxxx through 749TAFxxxx

Cause:
The Nickel Cadmium battery has relatively high internal impedance when it is fully charged. The HT750/HT1250 charger supplies a current pulse (1.2 Amps peak) for 5 seconds every 5 minutes, once the charger is in maintenance mode, which is similar to trickle charge mode in older chargers. The current pulse applied to the high impedance of the battery produces a voltage peak that can reach 12Volts during the time the charger current pulse is present. The radio electronic on/off switch will turn on, due to conduction of a 10V zener in the path of the electronic on/off switch transistor. The conduction occurs when the supply voltage reaches 11.4V.

Corrective Action:
Replace diode VR450 with part number 4802245J77 which is located near the flex connectors and can be replaced without removing any shields or the radio chassis. 

Please refer to the Professional Radio Detailed Service Manual (6881088C46) for exact component location.

Parts and $35 labor is authorized by warranty. Contact your local Motorola Authorized Service Representative to arrange for this modification. Agency Approved product should follow the guidelines for repairs and service.


* For international shipments contact your Motorola Regional Service provider.


If applicable, enter this information or note this bulletin number and subject material in the appropriate equipment instruction manuals and make necessary schematic diagram changes. Enter this bulletin in the correct MASTER and CLASSIFIED INDICES for future reference. Labor or parts warranty reference is limited to products sold and in use in the United States, for products sold or in use internationally this bulletin is for informational purposes only. Radios that are Agency Approved must follow designated agency guidelines.
SRN-ISO