Mackie_SWA_Diode_Swap_Service_Note电路图.pdf

Date: 6/04/2008 Subject: SWA 1501 Amplifier Service Bulletin Author: John Holme Revision History: 6/04/2008 Initial Draft First Revision Second Revision ? 12/10/2008 ?Third Revision, Scott Paterson - Affected Products SWA 1501 All serial numbers Failure Description SWA 1501 amplifier section, failing multiple times in short timeframes. Units fail to pass signal and sometimes actually emit smoke. Cause The misprinting of reference designators D19 (zener diode P/N: 82131050) and D20 (BAV21 diode P/N: 82112002) on the printed circuit board causes the problem, as the two locations numbers are swapped on the silkscreen. The correct components are being oriented correctly, but end up being in the wrong place. The picture below is an example of the INCORRECT silk screen. The CORRECT silkscreen sequence will be: R27, R28, R29, D19, D20, R30, D21 etc. Action When an SWA 1501 is being repaired for any reason, please look at the amplifier assembly and specifically at locations D19 and D20. If the locations are reversed from the schematics, install zener diode P/N: 82131050 in D20 and install BAV21 diode P/N: 82112002 in D19. Simplification The location next to R29 should have the Zener diode P/N: 82131050 installed. The location next to R30 should have the BAV21 diode P/N: 82112002 installed. Orientations are indicated by the silk screen, as this is correct. 1 of 2 RadioFans.CN 收音机爱 好者资料库 2 of 2 RadioFans.CN 收音机爱 好者资料库