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Post subject: Fender Champion 100 amp powers on but no sound
Posted: Wed Jun 28, 2017 8:55 pm
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Joined: Wed Jun 28, 2017 8:41 pm
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Purchased a used Champion 100 amp but am getting no sound through speakers. When I plug in the ear phones all features work. Inspected the circuit boards and everything looks good, no burned spots or swollen components. Anyone had this issue? Any ideas on which direction look for solution?
Thanks for any help out there.


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Post subject: Re: Fender Champion 100 amp powers on but no sound
Posted: Fri Jun 30, 2017 2:04 am
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Location: Province de Québec, Canada
Read same question on a forum few weeks ago .

Are you sure speaker is plug in the amp ?
Are sure speaker is good ?
If yes, IMO, the headphone jack do not work ; Contacts between amp and speaker are broken. Or solder on printed circuit.


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Post subject: Re: Fender Champion 100 amp powers on but no sound
Posted: Fri Jun 30, 2017 9:34 am
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To signal spilt the amp, try plugging your guitar into the Pwr amp in, (effects loop). I just tried this on my Champion 100. The jack was really stiff, almost felt like it was going to break, but any way the guitar volume was fairly loud.

The output signal is routed thru these jacks - Pre amp Out and Pwr amp In. From the Pwr In the signal goes to a opamp buffer then directly to one chip U400, a TDA8950J-1 which is the output power amp. You' d have to verify all power supplies that supply this chip. The IC itself is doesn't cost too much, but you have to check all other things before replacing that. Maybe the effects loop jacks are broken?

The Champion 20/40/100 schematic was on the web. Check Fender support.


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Post subject: Re: Fender Champion 100 amp powers on but no sound
Posted: Fri Jun 30, 2017 9:48 am
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There is a switch inside the headphone jack. If the headphone jack is damaged, it can affect the headphone detect circuit. Since the headphones still work, it could be bad solder on the switch pins of the jack. Resolder it and just for fun, inspect the traces around the jack with a loupe to inspect for broken traces.
https://www.google.com/url?sa=t&source= ... byWud62Qeg
It looks like Q401 is a power up delay circuit. Shorted zeners or a bad cap could be preventing it from unmuting.
The speaker mute signal is generated at the collector of Q2 when the headphones are plugged in.
Pin 23 on U400 is the mute control input. If it is unmuting, then its probably a blown U400.
Good luck.


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Post subject: Re: Fender Champion 100 amp powers on but no sound
Posted: Fri Jun 30, 2017 9:53 am
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I was just going to say that,, the headphone mute function,,,nice Tim.


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