Audio Asylum Thread Printer
Get a view of an entire thread on one page
|For Sale Ads|
In Reply to: RE: Bose Wave Radio/CD - Scratchy Noises When Off posted by MannyE on May 08, 2016 at 18:47:37
Thanks! Caps are easy, and are on my list of top suspects. However, I am getting no audible hum or buzz even with the radio on. If you put your ear against the speakers, with the volume at 0, you can still very faintly hear the music (but zero hum), but when you turn the unit "off" the music stops (and the scratchy noise starts), so there is a difference between "on" and "off".
I'm also thinking the issue is somewhere else - the output amplifier is misbehaving when it's partially powered off, or the power supply itself isn't fully off when it needs to be (letting small voltage spikes through to the amplifier). Or something else, who knows?
I am totally guessing at this point - without a service manual, it's all I can do. The radio isn't worth the cost of replacing parts till it works, so if the fix isn't simple and cheap, the radio will probably go back in the trash. If I figure it out, I'll post my results, in case it helps someone else.
I initially thought that there was a bad relay on the on/off circuit- but after reading the above post - that it actually does not turn off - but drops the volume - there may be an issue w/ the rt channel of the amp - having been driven into ground for so long- it may have a bad cap or tired transistor...
If you do revive it- you might put in a DPDT power switch - just to make sure it goes OFF -
I found the service manual and schematics on line (thank you Google). The output amp is an integrated part - TDA7375AV - under $6 from Mouser. I have a little more experimenting to do before I plug in my soldering iron, to see if I can isolate the source of the crackling noise. But with the manual and schematics/parts list, at least I'll have an idea what I am looking at.
Post a Followup:
Post a Message!
This post is made possible by the generous support of people like you and our sponsors: