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Author Topic: Fender Champion 30 - No output and channel switch frozen  (Read 314 times)

TSheld

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Fender Champion 30 - No output and channel switch frozen
« on: November 19, 2020, 12:20:16 PM »
Playing my guitar through this amp with the footswitch connected, all was good until I clicked the footswitch to go to the drive channel, the red light came on as it should but all output was lost.  Channel footswitch or manual switch now has no effect.  Has anyone had this happen and/or any ideas?

Enzo

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Re: Fender Champion 30 - No output and channel switch frozen
« Reply #1 on: November 19, 2020, 01:08:40 PM »
And did we unplug the footswitch?

Is the FS the real Fender FS for this model?  Or is it some stomp switch you had from something else?

Is there ANY sound in the speaker?  BAckground hum maybe?

Turn up the reverb and bang on the amp to crash the springs.  Does that noise come out?

g1

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Re: Fender Champion 30 - No output and channel switch frozen
« Reply #2 on: November 19, 2020, 01:27:13 PM »
Could have lost one of the supply rails.
Schematic attached.

TSheld

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Re: Fender Champion 30 - No output and channel switch frozen
« Reply #3 on: November 19, 2020, 06:05:46 PM »
Thanks Guys

Enzo
The FS is unplugged and is the factory FS that came with the amp
There is a very low hum from the cabinet speaker and the external speaker.
There is no noise from the reverb.

G1
Thanks for the schematic but I am just learning so not clear what supply rails are

Enzo

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Re: Fender Champion 30 - No output and channel switch frozen
« Reply #4 on: November 19, 2020, 08:07:21 PM »
Rail is just a informal term for power supply.  For example, your amp has a +27v and a -27v "rail", also has plus and minus 15v and also 13v rails.   There is no physical rail thing, it just means a point in the circuit that multiple things connect to.  SO in your schematic, every place you see a arrow pointing up with +27 next to it is connected to every other place with an up arrow and +27.   And that imaginary common point is the +27 rail.

SO as g1 suggested, check ALL of those supply voltages to see if any are missing.

TSheld

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Re: Fender Champion 30 - No output and channel switch frozen
« Reply #5 on: November 20, 2020, 12:28:16 AM »
Will do, thanks

TSheld

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Re: Fender Champion 30 - No output and channel switch frozen
« Reply #6 on: November 24, 2020, 05:45:42 PM »
Checked some supply voltages as best I could with my old multimeter. See amounts below on the the first 6 test points and then the 27volt supply rails going to the speaker output.  Definitely some weird stuff going on.
Any thoughts you have much appreciated. Thx

   Rated      Meter
TP1   20.3   V   AC   20.1    
TP2   20.3   V   AC   20.1
TP3   25.9   V   DC   26.0 
TP4   -25.9V   DC   0.8    
TP5   15.1   V   DC   14.2
TP6   -14.8V   DC   0.7    

TP17  2.97  V      AC    2.8   
U6-6   27   V   AC   58.5    
U6-4   -27   V   AC   1.2    
D22   27   V   AC   58.5    
D23   -27   V   AC   1.2    
R52   15   V   AC   30.2    
R55   -15   V   AC   28.3    

phatt

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Re: Fender Champion 30 - No output and channel switch frozen
« Reply #7 on: November 24, 2020, 07:59:49 PM »
You have lost the neg rail so the power supply is the issue. with TP4 dead none of the other TP's will read correct.
so first check the filter Caps and Bridge rectifier.
  Suspect parts are D13,14,15,16. and C36.  (If C36 is dead then I would replace C35 as well)
Once those are fixed the rest of the circuit TP's will likely be normal,, but check them after PSU is fixed just in case something else has been stressed.
Phil.