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Post subject: Fender The Twin, need some tube guru help
Posted: Thu Jan 20, 2011 11:17 pm
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I've posted this at The Gear Page, but no one has helped.

http://thegearpage.net/board/showthread.php?t=836897

I'm trying to read the schematic for The Twin (Red Knobs) and I can't really figure out how to read it in a way that will help me optimize my sound.

If someone can look at the schematic and list out all the tubes' jobs on the tube diagram below I would really appreciate it. I see that they are split in some functions and if you can explain that I would really appreciate knowing what each half is doing.

Also, if there are any players of this amp, tube recommendations would be great. I'm using it for high headroom cleans, country tones, and a platform for effects. Thanks.

http://www.ampwares.com/amp.asp?id=116

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Post subject: Re: Fender The Twin, need some tube guru help
Posted: Mon Jan 24, 2011 2:22 am
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Hi romulus333,

Do you know how the tubes on the chart are numbered? If so, could you post a chart with the numbers filled in, V1, V2 etc? I'm looking at "The Twin" red knob schematic, I hope it is the right one for your amp. There are two 12AT7s, one for the reverb driver (V8) and one for the phase inverter (V4). The rest of the preamp tubes are 12AX7. Each preamp tube has two halves (dual triode).

V1 half preamp, and half tone stack recovery for the parallel channel inputs
V2 additional preamp stages for switching channel inputs
V3 half preamp stage/preamp out and level select driver, and half level select recovery preamp stage (both channels)
V4 phase inverter
V5, V6 output
V7 half preamp stage and half tone stack recovery for the switching channel inputs
V8 reverb driver
V9 half reverb recovery, half preamp stage (both channels)
V10, V11 output

Let me know if this seems right to you. :idea:

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Post subject: Re: Fender The Twin, need some tube guru help
Posted: Tue Jan 25, 2011 1:36 am
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I have found out the position of the reverb and the phase inverter. The reverb sounded great with an 12au7. Concerning the position of v1, I thought it would be "b" since that socket is closest to the inputs. I took the guitar to an amp tech and he said v1 would be "a" in the picture below although he has not yet opened the case to the amp. I swapped out "b" with a nice RCA tube and it did make the tone change quite a bit.

The tech won't be able to "get to it" until Friday, so I won't be able to post a finished listing of the v1,v2,v3 etc until then. Is it common on amps for the v1 to be as far away as possible from the inputs like the tech suggested?

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Post subject: Re: Fender The Twin, need some tube guru help
Posted: Tue Jan 25, 2011 1:44 am
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On "real" blackface and silverface amps (and the BF dual-channel re-issues) V1 and V2 are located immediately adjacent to their respective channel controls on the chassis. Each of these tubes performs the first and second preamp gain stage functions of their respective channels (both tubes are dual triodes, ie: two tubes within a single bottle).

HTH

Arjay

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Post subject: Re: Fender The Twin, need some tube guru help
Posted: Wed Jan 26, 2011 1:16 pm
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I also have a Twin Amp, and hope someone can help me with some replacement tube advice.

I was playing through the gain channel, and I just slightly touched the gain knob and the whole channel went out, and would only play through the clean channel. I cannot get the gain channel back whether by pressing the button on the front of the amp or the footpedal. Also the tremelo went on, and I could only turn it off by turning the intensity knob all the way down.

Weird, huh?

Is this a preamp tube issue, and if so which one likely needs replacing? If not, what else might it be? THank you.


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Post subject: Re: Fender The Twin, need some tube guru help
Posted: Sun Jan 30, 2011 9:33 pm
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Hi Mike Kenny,

Are you saying that only one set of inputs on the amp work, and the other set doesn't? If so, which ones don't work? :idea:

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Post subject: Re: Fender The Twin, need some tube guru help
Posted: Tue Feb 01, 2011 11:54 am
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Shim,

Here's the problem. The lights on the foot pedal do not work. The push button on the face of the amp for the gain channel does not affect whether gain distortion cuts in or not. While the gain volume controls the overall volume, the sound is only that of the normal channel.

And as I mentioned the tremelo is always on, whether I push the foot pedal in or not. Same for reverb. The only way to cut out the tremelo is to turn the intensity dial all the way down.

Any thoughts?


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Post subject: Re: Fender The Twin, need some tube guru help
Posted: Tue Feb 01, 2011 12:04 pm
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Well, it doesn't sound like a tube problem at all. It may be a broken connection in the amp, like a bad solder joint/joints. Does it work with the foot switch unplugged, using only the amp controls? :idea:

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Post subject: Re: Fender The Twin, need some tube guru help
Posted: Thu Feb 03, 2011 9:42 am
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Shim,

I will check that out. And let you know. Lucky for me it's not my only amp.


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Post subject: Re: Fender The Twin, need some tube guru help
Posted: Mon Feb 07, 2011 10:36 am
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Shim,

I don't know how you figured it out, but when I unplugged the footswitch, everything worked again. Thank you!

Of course now I don't have a working footswitch, but i will deal with that. Heh.


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Post subject: Re: Fender The Twin, need some tube guru help
Posted: Mon Feb 07, 2011 3:35 pm
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Cool! 8) Make sure that it is the correct foot switch for your amp, sometimes they get mismatched which wouldn't operate properly. If it is the correct one for your amp, then maybe it needs to be repaired. There isn't much to the foot switch, a few diodes and a couple of switches, and would be easy to check with a meter. At least you can use your amp now. :) :idea:

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Post subject: Re: Fender The Twin, need some tube guru help
Posted: Wed Feb 09, 2011 9:10 am
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Shim,

It's the right footswitch alright. Used to work fine. I will open it up and see if maybe it just needs some soldering.

Thank you again, very much.


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