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Post subject: Fender Tone Master hummmmmm
Posted: Sat Mar 12, 2016 4:51 am
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Good morning,

Looking for a quick thought or two about a new to me Fender Tone Master head. It just arrived yesterday. So I turned it on and powered it up. As soon as I clicked it from standby, I noticed a continual hum, probably 60 cycle like a ground jump needing hum. It isn't super loud and you wouldn't notice it while you're playing, and it does not change when you turn up the volume. It does it on both channels. It also gets louder when I move the impedance selector switch to the low setting, and is quieter but still there in the high position. I haven't played it a ton yet as my daughter was asleep when I got home last night, but it seemed to be operating fine when playing at very quiet volumes.

I'm just trying to figure out if it seems like it's something big component wise or maybe just a bad tube before I accept this amp. Any help would be super appreciated. Much thanks.

Dave


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Post subject: Re: Fender Tone Master hummmmmm
Posted: Sat Mar 12, 2016 6:02 am
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Quick update. Just played it for about 15 minutes or so. The hum definitely isn't noticeable when playing. It is definitely way more noticeable on the clean channel, and overall the high end seems out of control to me, even compared to my Super Sonic 60. Like I feel like I could completely dial down the treble on the clean channel and it's still super bright.

Thanks for any insights you guys might have.

Dave


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Post subject: Re: Fender Tone Master hummmmmm
Posted: Sat Mar 12, 2016 6:44 am
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How long do you let the tubes warm up before taking the amp off of standby? In my case, I get less hum if I power up the amp with it in standby. I then tune up and some other prep items that take a couple minutes. I then take the amp off of standby and it is quite quiet.

I currently have a Supersonic 22, but used this on my old Blues Deluxe as well. Worked great.

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Post subject: Re: Fender Tone Master hummmmmm
Posted: Sat Mar 12, 2016 10:26 am
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Yeah, I let it warm up about 5 minutes before taking it off standby. I've had lots of fender amps (SS60, SS22, Twin Amp, Super) and none of them hum like this. It's definitely like 60 cycle hum. I just am trying to figure out if it's potentially something big wrong or possibly just tubes. I feel like from past experiences with bad tubes, it was usually hissing and popping that indicated tube issues. I've never had one with constant hum.


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Post subject: Re: Fender Tone Master hummmmmm
Posted: Sat Mar 12, 2016 10:28 am
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I'd guess the amp is ready for new filter caps. I'd recommend F&T's as the best available. Their service life is easily twice or three times that of the OEM components. Once replaced, the B+ high voltage and bias-supply current should be checked, with the latter adjusted if necessary.

Arjay

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Post subject: Re: Fender Tone Master hummmmmm
Posted: Sat Mar 12, 2016 11:42 am
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A good shape amp don't make hum or hiss or..if in Stanby less than 1 minute.

If need more to be quiet ,tube(s) may be weak.


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Post subject: Re: Fender Tone Master hummmmmm
Posted: Sat Mar 26, 2016 2:51 pm
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Any update(s)?

Arjay

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Post subject: Re: Fender Tone Master hummmmmm
Posted: Mon Mar 28, 2016 7:31 am
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Arjay was right on with filter caps being the issue. Apparently one was bad, and one had actually broken off on one end (might have been the same one , I can't remember exactly how it was now.

Thanks very much for the remote trouble shooting. It is now quiet as it should be, but very very bright. I'm making a new post for some thoughts about that issue. Thanks again.

D


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Post subject: Re: Fender Tone Master hummmmmm
Posted: Mon Mar 28, 2016 7:39 am
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Excessively bright tone is often associated with the bias current incorrectly set. Was that checked after the new filter caps were installed?

Arjay

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Post subject: Re: Fender Tone Master hummmmmm
Posted: Mon Mar 28, 2016 7:44 am
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Retroverbial wrote:
Excessively bright tone is often associated with the bias current incorrectly set. Was that checked after the new filter caps were installed?

Arjay


+1, look a cold bias

I agree what Tom Stewart of SpaceMan Music , Ottawa, said about bias :

" Under-biased amps will lack punch and the tubes will run noticibly hotter.
Over-biased amps will sound thin and brittle, with the tube running too cool for proper performance.
A correctly-biased ampsd will sound clean and tight at moderate volume, then at higher volumes break up and distort musicaly."


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Post subject: Re: Fender Tone Master hummmmmm
Posted: Mon Mar 28, 2016 6:42 pm
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Yeah the bias was checked after. We're getting together Wednesday to look into negative feedback and maybe bypassing some of the high pass. Supposedly overly brightness is a somewhat common problem with Tone Masters. I guess rolling the dice with amp purchases doesn't always work out so good.

Thanks for the ideas.

Dave


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Post subject: Re: Fender Tone Master hummmmmm
Posted: Mon Mar 28, 2016 6:56 pm
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Dmerch1969, do you have access to the schematic for this amp? Values of coupling caps used between stages could also lend a clue to the brightness issue.

Cab speakers work well with other amps?


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Post subject: Re: Fender Tone Master hummmmmm
Posted: Mon Mar 28, 2016 7:22 pm
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http://support.fender.com/schematics/guitar_amplifiers/Tone-Master_schematic.pdf

The cab I've played it with is a 4x12 tone master. It is loaded with Celestion vintage 30's. I have also hooked it into my super amp speakers which are 4-10" Eminence Legend 1058's. Same results with both setups. Gain channel is only barely useable with gain at 3 or below and the treble knob dialed all the way back to zero. Clean channel treble knob 2 or below. Not a lot of low end punch either.

Thanks.

Dave


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Post subject: Re: Fender Tone Master hummmmmm
Posted: Mon Mar 28, 2016 9:03 pm
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The Tonemaster has an interesting input stage. Esp the cathode of that half of the 12AX7. A voltage reading point. And what seems like a 1mfd/35VDC bypass cap tied to that point. Then, to ground via a 22k-ohm resistor. The usual 1.5k-ohm cathode resistor running parallel to this read-point/cap network.

My guess is a typical 25mfd/50VDC cap running parallel to the 1.5k-ohm cathode-tied resistor may help tame some of the high-frequency. Give more weight to the bass and midrange.

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Post subject: Re: Fender Tone Master hummmmmm
Posted: Tue Mar 29, 2016 1:22 am
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If you don't like this amp's tone, sell it and buy a amp you'll like the tone and listen it before you buy .

If you have some skill in electronics you can try to mod it but you'll never be sure it will sound good for you.

Is it a printed circuit ? If yes this is not easy to mod.


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