My Bose wave radio Model AWR1-1W had no sound, no display, and when the power cord was disconnected there was a sound like a needle scratching a vinyl record. It seems these symptoms are common, and many times the fix has been to replace the transistor in the Q4 position on the circuit board. I was able to repair it!! Below are the details in the hopes it will help others.
First thing, i tested the fuse near where the power cord attaches. Fuse was ok.
I looked up the parts on the NTE Electronics web site. The original transistor is a 2SC3792. This cross references to NTE85. But I read comments online that the 2SC3792 was undersized, which is why it has failed in numerous radios. So i didn’t order the NTE85, even though i read that it works for this.
For some, 2SC2655 has worked as a replacement. This crosses to NTE2363 which is available.
I read that a Bose tech had recommended a "beefier"part, 2SD438F. This crosses to NTE382, which is available.
I ended up installing NTE2363. It's bigger than NTE85, and others have had success using it as a replacement.
Before removing the old transistor, take photos of both sides of the board near the transistor, as a reference. When new transistor arrived i used multimeter to test the new and the old part. Sure enough, the old part was shorted out. This is a bipolar junction transistor, type NPN. For testing the old transistor after removing it, the pin arrangement (pinout), looking at the flat side of the transistor with leads below (left to right), is E, C, B (Emitter, Collector, Base). Testing instructions can be found online.
The soldering job has an extra twist. On the top side of the circuit board, there is a wire coming from another component (capacitor?) that has to be soldered to one of the leads.
After i soldered in the new part, the radio still didn’t work. I did some continuity testing and discovered the middle lead was not connecting to the circuit in the board. So i added more solder to connect the lead to the “solder bump” along the circuit path. After this the radio worked.! I almost gave up but perseverance paid off.
In summary, if u test the old Q4 transistor and it's bad, chances are pretty good a new transistor will fix it. But after soldering, test to make sure the leads are connected to their circuit in the board (see attached drawing). And make sure the solder from adjacent leads isn’t touching.