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Post subject: Ever plug your foot switch in the extension speaker output?
Posted: Tue Sep 28, 2010 1:25 pm
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So, trying to see why my reverb was not working, I reached behind my Twin Amp and plugged my foot switch into the extension speaker output. The amp was then turned on and allowed to warm up and I then hit the stand bye switch. (Question 1)What do you think this physically did to my foot switch? I'm thinking whatever amount of current comes out of the ext. spk. output could not have been good for the foot switch. Also, with the foot switch now in the foot switch output, I can't get any lights on the pedal to come on and when I stomp any button as many times and as hard as I can, nothing happens.
I bought this amp new almost 5-years ago and I may have gigged 5 times with it. I have a DSP 100 and it's lighter to handle, but my ego made me buy the Twin. I don't ever remember the reverb working on the Twin with or without the pedal. (Question 2): is there a tube associated with the reverb?
Of all my tubes, the GT-12AT7 does not seem to be glowing anywhere near as bright as all the other tubes. My overdrive channel works just fine, which I thought this tube was associated with. Hope all I need to fix this is a tube and a new foot switch. This ever happen to you? Would you share your fix with me?


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Posted: Tue Sep 28, 2010 1:47 pm
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No offense meant, but with your track record for amp repairs, I suggest taking the amp to a pro. How bright a tube glows is no indication of how well it is working, unless of course, it is glowing red hot!

Here's the schematic:

http://support.fender.com/schematics/gu ... ematic.pdf

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Posted: Tue Sep 28, 2010 1:53 pm
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As far as the speaker signal is AC I don't see any reason that this connection killed your footswitch excepted at start-up where a transient voltage and current can occur or if you play like led zep; The risk is for your transfo and power valves due to the fact that there no load for the secondary bring back to the primary. This load is again AC, then if you don't play (only DC mode apply) and waited in this position there is no reason of big issue usually "smoke". this my point of view.
The reverb associated valves are V5 (12aT7) and V6A (12ax7).
The footswitch can be repaired. 8)

+1 to bluesky

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Posted: Tue Sep 28, 2010 2:34 pm
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Alternatively, check the reverb tank. Alsorts of stuff in there can go wrong like the springs breaking or the pickup inside the tank being broken.

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Post subject: Re: Ever plug your foot switch in the extension speaker outp
Posted: Tue Sep 28, 2010 4:21 pm
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River Dan wrote:
(Question 1)What do you think this physically did to my foot switch?...


Probably just a blown diode or two (LED), might have popped like a fuse. :idea:

River Dan wrote:
(Question 2): is there a tube associated with the reverb? Of all my tubes, the GT-12AT7 does not seem to be glowing anywhere near as bright as all the other tubes....


The 12AT7 will not glow as bright as the 12 AX7, that's normal. It is also the reverb driver tube, from the schematic, I wouldn't put a 12AX7 in that spot (V5). Like Big The Cat said, the reverb problem is likely in the tank, or the wires to the tank. :)

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Posted: Wed Sep 29, 2010 7:53 am
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Blue Sky636, You nailed it "my record of amp repairs" is indeed non-existent. I want to thank you for the schematics and your time. I didn't know that about the brightness of the glow of these tubes. The 'glow' from the 12AT7 almost looked like it could of been reflection from the other tubes. I will check it out again, very carefully, and see if it is warm. Fortunately it was not glowing red hot. Big The Cat I am fairly good with an ohm-meter and have checked all the wiring to, from and through the reverb springs and all was well. I did this before my plug in incident/accident. Tissan, fortunately, while it was plugged in wrong, I only hit the strings once, looking for that reverb sound. And, really fortunately, there was no smoke or electrical smell from the amp or foot switch. And, don't I wish I could play like Jimmy Page! Thanks for the AC/DC explanation. Shimmilou, I hope you're right about the led's. They would have to be a part of the circuit controlling each individual button, as I can't a response from any of them. Fortunately (?) I did have everything plugged in before I turned the amp on. I promise not to put a 12AX7 where the 12AT7 belongs.
So Thanks everybody for helping me learn a few things about my amp. I'm replacing the foot switch and the tube first because, if this does fix it, it would be equivalent to the bench charge for just opening it up to repair it. If it does not fix it, I have a spare brand new foot switch and a 12AT7 tube for sale. Great forum, great products, great people. Live happy.


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Posted: Wed Sep 29, 2010 8:24 am
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Good tips here and I'll throw in another one,all electronics are filled with smoke,and when they develop a leak you will see it. :lol:
I've seen it before. :wink:


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Post subject: Footswitch into speaker jack
Posted: Wed Sep 29, 2010 10:38 am
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Don't forget Rebelsoul, that smoke is put into the components at the factory (factory smoke not available to public). Once you let the smoke out, you can't put it back in. :lol:

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Post subject: Re: Footswitch into speaker jack
Posted: Wed Sep 29, 2010 11:09 am
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shimmilou wrote:
Don't forget Rebelsoul, that smoke is put into the components at the factory (factory smoke not available to public). Once you let the smoke out, you can't put it back in. :lol:


LMFAO!

"I'm a doctor, Jim......not a miracle worker!"

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Posted: Wed Sep 29, 2010 11:19 am
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Rebelsoul wrote:
Good tips here and I'll throw in another one,all electronics are filled with smoke,and when they develop a leak you will see it. :lol:
I've seen it before. :wink:


Quick off topic post:

Speaking of smoke, in college I worked at a small electronics company that built radio switching gear. I started in the assembly shop and moved up to the lab. The lab manager (the owner's son) tasked me to make a small mod to one of the switching boxes. It was less than half a dozen components and didn't take long. When I was done, I decided to check it out so I flipped on the power switch. 8) You guessed it. SMOKE! :shock: I watched in horror as several ICs literally went up in smoke. I quick flipped it back off and waited for the manager to return, unsure of my fate. :?: Amazingly, they didn't fire me on the spot. :D But they did send me back to the assembly shop. :oops:

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