Mackie SWA Diode Swap Service Note
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Extracted text from Mackie SWA Diode Swap Service Note (Ocr-read)
Page 1
LOUD Technologies Inc.
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 fall 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.
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