Fender Mustang II amp no output, looking for schematic

[Dehn]

Hi All fellow repair techs,

I'm working on a Mustang II amp with no output, first I thought it would just changing the TDA7294 IC, which I did, still no sound.
After looking up the IC's specs and getting some voltage info, I found the mute and standby voltages were missing.
Using two 9v batteries I replaced the missing power to the IC, and the amp came on.
Without a schematic this looks like a real tough repair to find the problem, does anyone have a schematic of this amp?

Regards
Dean C

[Jazz P Bass]

If you do not have a schematic on hand, make one.

Follow the mute pin back & draw it.

Marshall uses a transistor & a zener diode/ capacitor to slower ramp up the voltage (anti turn on thump).

[Dehn]

Hi jazz p Bass

Thanks for the reply, IF it was a Marshall I could do that, the problem is its all surface mount components and has a large micro processor board mounted on top of it.
The mute voltage is not coming from the switching power supply directly cause I've checked that out already.

Regards,
Dean

[52 Bill]

I haven't been inside one, but check the input jack it could trigger the mute as well as the headphone jack, etc.

[Enzo]

So call Fender and ask for the schematic.

[Dehn]

Thanks for the idea Bill,

I checked the jacks and they are good.

Regards
Dean

[Dehn]

Thanks Enzo,

But I am not an authorized service repair center for Fender.

Regards
Dean

[Enzo]

And you don't always have to be. Call them, the worst that could happen is they say "no."


Never think up reasons not to check something.

[Jazz P Bass]

I would check the resistance of the mute pin to ground.

If it's open, then something in the mute circuit is blown.

At that point, find a 5 volt source & hook it up to the pin.

[petard]

Hi Dehn, I have the same problem, how can I fix it? Thanks is my first time in this forum

[vintagekiki]

Fender Mustang schematics

http://music-electronics-forum.com/t19518-2/#post444564

[petard]

thanks vintagekiki
But I already have the schematic of the amplifier, my problem is that I have no voltage in the mute or stand by, I have no sound at the output, I see that comes from the transistor Q100 2N4403 ,
That's why I ask if that's the problem, sorry my English i´m Spanish

[Dehn]

Hi Petard,

After begging to Fender at least four times, someone did send the schematics.
It was a bad 15 volt regulator IC either U107 or U108 I don't remember it was a couple years ago.

regards
Dehn

[petard]

Ok Dehn thank you so much,i will watch IC ,i hope that's the problem, this IC is on the motherboard?

[vintagekiki]

Mustang main board schematics page 6
U107/ U108 positition on schematics A (left) 5 (down)