[Scott B]

I have enjoyed my Onkyo A-9555 amplifier for about a year now.  I love how it sounds.  I just bought a hi-fi tuning fuse for it and it wasn't until I received it in the mail and installed it in the amplifier that I realized that I ordered it with the wrong Amp rating (1.6A instead of 6.3A).  That was stupid! back to the stock fuse for now.

Here's the Problem:
when I put the stock fuse back in and turned the amp on again it sounded terribly fuzzy and distorted, especially in the higher frequencies.  Also, it would occasionally just shut itself off.

I'm not sure what could've happened.  I made sure to wait a few hours with the amplifier unplugged before opening it up.  I tried to clean the fuse contacts and I even tried putting in a brand new fuse.  the amp still sounds crappy and occasionally wants to shut itself off.

I'm really hoping nothing is permanently damaged and any Ideas what might be causing the problem would greatly appreciated.

Thanks,
Scott       

[Scott B]

Anyone?

[eclein]

I'm not very knowledgeable about fuses but it sounds like to me that when the wrong fuse was briefly installed it damaged the circuit
somehow?? Somebody here will know better..Good luck.

[srb]

The new specialty fuse that was installed was smaller (1.6A) than the standard fuse (6.3A).  The only problem putting in a smaller fuse might cause is blowing the fuse under moderate and higher volumes.
 
Perhaps something was physically tweaked when removing the old fuse, like partially cracking a circuit board trace while prying it out, etc.
 
Steve

[Scott B]

Thanks for the replies.

eclein - god I hope not!

Steve -  the fuse being a lower amp rating would blow before it causing damage to the amplifier was my assumption as well.  Something I forgot to mention is that the lower amp fuse actually did not blow, which is surprising because I did crank the volume up a bit.   Come to think of it while the 1.6A fuse was in place I did hear those same fuzzy characteristics that I heard when I put the stock fuse back in.  That leads me to believe that, as you said, perhaps the board was "physically tweaked" when removing the stock fuse.  I'll look at it again and maybe it's just a loose solder connection between the fuse holder and the circuit board.  I hope the board is not cracked itself.

Scott

[srb]

Yes, hopefully there is no damage to the board layers themselves.  I assume that you get the same fuzzy sound in both channels, which would point toward something common to both channels, like the power supply.
 
Check any components around the area, particularly capacitors that have some height (versus small surface mount caps) that might have had some torque applied against them.
 
Otherwise, I will also assume that you made no changes in the AC supply, for example plugging the amp into a restrictive power conditioner versus directly into the wall.
 
Good luck, let us know if you discover anything.
 
Steve

[Scott B]

Steve-
yes, I the fuzziness is both in both channels.   the picture of the circuit board was snagged from off the internet,  but it shows the area next to the fuse.  if it's not the fuse holder itself those blue caps might be potential culprits.  I'll check them tonight give an update to what I find out.

Scott

[Scott B]

Okay so I pulled the circuit board out and found that nothing looked cracked or there were no loose solder joints.  I put the amp back together, turned it on and for some reason the problem was no longer there.  The amplifier sounds good again.  not sure what I did differently but everything's back to normal.

Thanks for the replies,
Scott