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TOSHIBA SB-420: Explosions in the Sky!!!

cscottrun4it

cscottrun4it

Active Member
TOSHIBA SB-420: Help!

I'm a newbie at a lot of this, so be patient Jedi masters. I bought a Toshiba SB-420 after doing a lot of research. I wanted something that would drive whatever speakers I settle on and allow me to run a TT, R2R, and tuner. The 420 is a great integrated amp and has not disappointed. The sound is beautiful, and the amp itself is beautiful, which is the cherry on top.

But... and you knew that was coming.

Yesterday, the amp began randomly issuing forth explosions of static, snarls, and pops. These occur at full volume, no matter where the volume is set. It scared my kids and dogs near to death! :dammit:

Because of the sonically violent nature of the illness, I have not spent a lot of time in diagnosis. As for the electronics, I don't even know where to start with diagnosing what might be wrong, or if I start by sending it off to "the shop," whatever that means.

I would really love to have some idea what is wrong with my new love before I go to "the shop." Or, better yet, be able to cure her my self.

Thoughts?
 
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Because the volume control has no effect on the explosions, I'd suspect the power amp section. Was the sound "normal" between events?
I notice that you can separate the poweramp from the preamp. If you have another amp, connect the pre out to an aux in and see if the issue occurs.

Here's a service manual:
http://elektrotanya.com/toshiba_sb-420.pdf/download.html
 
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Both channels? If so, could be loose grounding of the amplifier board. Try tightening the screws, especially if it isn't insulated and on a pcb pad. Also, look for bad solder connections. Could be anything.... Get a pair of disposable speakers for testing. If just one channel, it probably is a bad transistor, but hard to tell. Good luck with it.
 
EchoWars said:
OP was 19 months ago...
Click to expand...

I know, I know... :sigh:

Only stumbled on this post by Googling SB-420, simply because I have one. And (without checking the schematic), the mic amp appears to couple straight into the power amp stage - and DC on the mic gain pot causes full level crackles on the output, irrespective of volume control setting.

Just trying to be helpful, that's all...
 
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