HarrisAM-466-TLH_0896电路图.pdf

HARRIS CORPORATION P.O. Box 4290 3200 Wismann Lane Quincy, Illinois 62305 217/222-8200 BULLETIN NO: AM-466-TLH DATE: August 1996 Updated: Feb 2004 EQUIPMENT: AMS-G1 Stereo Generator SUBJECT: Pilot Crystal Circuit We have determined that the signal level within the Y1 pilot crystal circuit may be too high, leading to failure of the crystal and complete loss of the 25 Hz pilot. This bulletin addresses this concern with changes to reduce the signal level applied to the crystal. Note: This is independent of the Pilot Level adjustment. Adjustments to pilot level will not resolve this problem. Please make these changes as soon as conveniently possible. Tools Required: 30W pencil soldering iron, de-soldering tool, wire cutters, Needlenose pliers, Screwdriver Parts included at no charge: Qty Part Number Description 1 444-2993-000 Crystal, 25.6 Khz 1 516-0453-000 Cap, 0.1 uf 1 548-2400-634 Resistor, 2.21 Meg ohm Procedure 1. Disconnect the AC power and any connections necessary to allow reasonable access to the top of the AMS-G1 Stereo Generator. 2. Remove the top cover to gain access to the Stereo Generator board. See drawing. 3. It is possible to make the changes without removing the circuit board. However, if you prefer to remove the board so that you have access to the bottom of the board, please use the following steps: a. Remove the plastic safety cover from the PDM Sample connector. You will need a 5/16” nut driver for this. b. Unsolder the wires from the PDM Sample connector. RadioFans.CN 收音机爱 好者资料库 AM-466 Page 2 HARRIS CORPORATION P.O. Box 4290 3200 Wismann Lane Quincy, Illinois 62305 217/222-8200 c. Remove the 6 screws which fasten the rear panel in place. d. Unplug J1 and J8. e. Remove the mounting screws from the board (Qty 14), and screws which fasten the aluminum heat sink in place on the right hand side (Qty 2). f. Lift the board so that it clears the power transformer, and slide it out the rear of the chassis. 4. A new crystal is being provided in case yours has failed. It is otherwise not necessary to replace it. Note that if you need to replace the crystal, take care to avoid overheating it while soldering the connections. 5. Remove the existing R170, and replace it with the enclosed 2.21 Meg ohm resistor. 6. Add a 0.1 uf capacitor, C213, across R175. 7. This completes the modification. Reinstall the hardware and connections removed in the preceding steps. If you have any questions or comments concerning this bulletin, please contact: Harris Broadcast Radio Field Service P.O. Box 4290 Quincy, Illinois, USA 62305 217/221-7528 Fax: 217/221-7086 Telex: 650-374-2978 Haris UR RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 Revision E: Piggy back a 0.1 uF ? capacitor C213 516-0453-000 across ? R175. If replacing Y1, ? avoid overheating it ? when soldering the ? connections. Replace R170 with a 2.21 Meg ohm resistor ? part number 548-2400-634 Revision F:? C213 is ? standard.