Fender Bassman 100T Chapter 3

[GG7]

thanks for pointing that out. That's one feature I haven't messed with yet. Though I'm confused a bit. Wouldn't "Full tilt boogie" produce a dirtier/more aggressive sound? I can see that the cooler setting might be an option for channel 1, but I wouldn't want to "tame" channel 2 at all. Do these settings affect output level? I am inclined to think not but there have been a few times in my life that I was actually "not right". Anyone? next time out at the shed I will experiment a bit though it would be nice if I was little more informed before tweeting knobs.

Hey Ron,

I would play around with those switch positions and see if you can achieve your intended goal. I would try using the WARM position for a while and see what you think. That switch changes how hard the 6L6s are driven. I have always run mine on NORMAL because I am using four vintage GE 6L6GC power tubes that I bias matched using my Triplett 3444 vintage tube tester and some other gear.

The GEs prefer to be driven at the level the 100t's NORMAL setting provides, but in the case of Russian made tubes, you are totally safe running them in the WARM position and see if you prefer that amount of headroom and overall tube warmth/distortion.

 

[GG7]

Also wanted to touch on the whole Auto-Bias debacle early on in this amp's production life... I think I posted some results in this thread a long, long time ago when that Auto Bias issue was still effecting that small number of new 100ts.

I never personally had a single problem with my amp and the Auto Bias has always worked great for me. And it was in relation to that, that I posted some interesting results during my tube rolling project a few years ago.

I actually took some KNOWN problematic 6L6 tubes (not shorted, but definitely with issues) and loaded them into my 100t, just to see how "observant" the 100t's auto bias system was going to be in identifying potential "issues' with these borderline power tubes.

The results were impressive and at the same time VERY comforting! Your typical budget price vintage tube tester would have a hard time detecting the issues with these 6L6s that I tried to fool the 100t with. Only something on the order of my Triplett 3444 tube tester would have the ability to detect the underlying problems, but TO A TUBE! The 100t checked and identified every one of these suspect 6L6 power tubes as having a problem, and the amp gave every single one of them a failing grade, and with that refused to "light them up"!

It was at that point that I went from being somewhat on the fence with this new Fender Technology to an instant MEGA FAN of Fender's Auto-Bias feature! The results told me, that everyone who owns a 100t has got a very sophisticated power tube tester built into their already wonderful amp! It detected issues that previously took a very high end tube tester to uncover!

So contrary to what "some' misinformed critics continue to claim, the Fender Auto-Bias feature is a Godsend for 100t owners whether they realize it or not!

 

[Freight Train]

Train, that's why I really want to demo first. I'm not disappointed with the 100T at all and I don't feel it lacks punch. Simply, there are occaisional times when I just need a little more "oomph" on the clean side without slamming the front end. With my set up/signal chain getting above 6 on the gain starts to get away from the creamy bliss of this channel. There's still nice breakup at 6, not wanting to eliminate it. Thats why I'm wondering if just a tad bit more air from cab would deliver results. I'm also going to play around with getting my signal chain below unity and see if that makes a difference.

Did you say that you're able to get that little extra from the active channel, but it's the vintage channel that chokes before it gets there? Both of the channels use 1/2 of V1 for their first stage, but where the overdrive channel has an op-amp second stage, the vintage channel uses the 2nd half of V1. So I'm guessing it's that second tube stage that is choking up when you drive it too hard. I think you had asked about putting an overdrive in the preamp/amp loop, but that would be no different than just turning up the master. Do you have a hot bass? Have you tried using input 2? Or are you using input 2?

 

[shwashwa]

Also wanted to touch on the whole Auto-Bias debacle early on in this amp's production life... I think I posted some results in this thread a long, long time ago when that Auto Bias issue was still effecting that small number of new 100ts.

I never personally had a single problem with my amp and the Auto Bias has always worked great for me. And it was in relation to that, that I posted some interesting results during my tube rolling project a few years ago.

I actually took some KNOWN problematic 6L6 tubes (not shorted, but definitely with issues) and loaded them into my 100t, just to see how "observant" the 100t's auto bias system was going to be in identifying potential "issues' with these borderline power tubes.

The results were impressive and at the same time VERY comforting! Your typical budget price vintage tube tester would have a hard time detecting the issues with these 6L6s that I tried to fool the 100t with. Only something on the order of my Triplett 3444 tube tester would have the ability to detect the underlying problems, but TO A TUBE! The 100t checked and identified every one of these suspect 6L6 power tubes as having a problem, and the amp gave every single one of them a failing grade, and with that refused to "light them up"!

It was at that point that I went from being somewhat on the fence with this new Fender Technology to an instant MEGA FAN of Fender's Auto-Bias feature! The results told me, that everyone who owns a 100t has got a very sophisticated power tube tester built into their already wonderful amp! It detected issues that previously took a very high end tube tester to uncover!

So contrary to what "some' misinformed critics continue to claim, the Fender Auto-Bias feature is a Godsend for 100t owners whether they realize it or not!

its a great feature if it works! i got my 100T in december, it crapped out immediately, and i finally got it back 2 weeks ago. that's a hell of a long time to be without a brand new amp for a "simple" repair. if it holds up ill be very happy. my personal gripe was with the ridiculous amount of time it took to repair and the complete lack of communication during that time.

 

[PhatRon]

Did you say that you're able to get that little extra from the active channel, but it's the vintage channel that chokes before it gets there? Both of the channels use 1/2 of V1 for their first stage, but where the overdrive channel has an op-amp second stage, the vintage channel uses the 2nd half of V1. So I'm guessing it's that second tube stage that is choking up when you drive it too hard. I think you had asked about putting an overdrive in the preamp/amp loop, but that would be no different than just turning up the master. Do you have a hot bass? Have you tried using input 2? Or are you using input 2?

What I mean to say is a little more gain/ slam on the front end of channel 2 sounds desirable. not so on channel 1 when I am wanting a nice smooth creamy sound ( i'm not gonna say clean or clean channel as this rig is not really about that). My bass is passive and I attempt to set my pedalboard at unity gain. Maybe that is perceived and not actual. I am going to mess around with lowering output at board and see if that reacts better or raising it a tad and using input 2. I also have some work to do figuring out how to balance inputs as I just purchased an Ibanez ATK805E which is active. I may need to run into input 2 and use boost when playing my jazz.

Did I just call this work? This is gonna be fun!!! I am taking next two weeks off from work which coincidentally lines up with prepping for upcoming session.

Train, if I recall correctly you use an L1K. That's a hot passive input for sure. where do you input?
I sold my two 81's to fund the Fender rig. One of my few "good moves" I'm usually the buy high (maybe that's the problem), try, sell lower. Pay a little to demo-not the end of the world I suppose.

 

[PhatRon]

ts a great feature if it works! i got my 100T in december, it crapped out immediately, and i finally got it back 2 weeks ago. that's a hell of a long time to be without a brand new amp for a "simple" repair. if it holds up ill be very happy. my personal gripe was with the ridiculous amount of time it took to repair and the complete lack of communication during that time.

wow that is a mighty long time. was it Fender or a dealer/authorized repair service that was the problem? I am rooting for you to start enjoying a wonderful amp issue free.

 

[shwashwa]

wow that is a mighty long time. was it Fender or a dealer/authorized repair service that was the problem? I am rooting for you to start enjoying a wonderful amp issue free.

authorized dealer sent it to fender for the fix.

 

[Freight Train]

Train, if I recall correctly you use an L1K. That's a hot passive input for sure. where do you input?
I sold my two 81's to fund the Fender rig. One of my few "good moves" I'm usually the buy high (maybe that's the problem), try, sell lower. Pay a little to demo-not the end of the world I suppose.

I'm using input 1, but I rarely use the super boost on the L1K - just now and again for effect - but it doesn't seem to stress the input even then. Normally just rock it in single coil mode and that works great.

 

[PhatRon]

made some adjustments to output levels on signal chain. It did amount to some improvements on channel 1. It actual opened up channel 2 a bit also. Rig sounded awesome at rehearsal. I still would like to audition the neo 610 however I'm not going to purchase to do so. Hopefully an opportunity will present itself.

 

[DJS]

Great thread, but I need a little help from 100T veterans. I've been using my 100T lightly (weekly rehearsals, 6 or so gigs) for about a year, and bought it from a reputable seller here. Last night, in the middle of a song, it failed. Looks like the main fuse is blown, and there was a telltale burnt electronics smell. I noticed one tube still glowing, albeit weirdly, afterwords.

I don't mind using a screwdriver, replacing fuses, or even tubes, but want to make sure not to mess anything up further. I'm tempted to replace the fuse, but whatever failed is likely still present. I need some advice on my next most logical step, with a gig in 2.5 weeks.

Thanks!

 

[rodl2005]

Are yr bias lights yelling you anything?

 

[DJS]

Are yr bias lights yelling you anything?

I replaced the fuse and powered it on (standby only) this morning. It initially showed a failure with 1A, but after about 10 minutes or so, everything went to all green. Ah - now I see it's back to flashing red/orange for 1A/1B. So a bad tube can cause the main fuse to blow?

 

[rodl2005]

I would think so. @beans-on-toast
He should be able to help you get more than I can.

 

[DJS]

I would think so. @beans-on-toast
He should be able to help you get more than I can.

Thanks! Pulled the tubes out, and one (the flashing red 1A) is definitely burned looking. It's oddly shorter than the other three as well (by almost 1/4 inch) yet carries the same numbers. I assume Fender puts their name on these, but some variations might be possible depending on the manufacturer.

 

[beans-on-toast]

Low line voltage at a gig can can cause problems. It is also possible that the tube failed. The fact that the tube looks different should not be an issue. I assume that the tube set was matched as per their specs.

When a tube fails, an amp has safegaurds built in to minimize damage to the amp and shut it down. The fuse blew. On some amps, plate and cathode resistors are designed to blow. They act like fuses and protect further damage. If this happens, they will need to be replaced. The heater of the tube will glow but the tube will not work.

The auto bias circuit in the 100T is supposed to take care of issues like this and should protect the amp by shutting down the tube.

One option is to replace the tube and carefully see if the amp works normally. If autobias did its job, everything will be fine. Replacing the tube should reset the bias circuit and the LED's should indicate that all is well. This only happens when the new tube is installed.

If you are concerned that the damage was more extensive, have a tech check out the amp to ensure that there wasn't any damage. Obviously this is the safer option but it will cost you time and money.

 

[DJS]

Low line voltage at a gig can can cause problems. It is also possible that the tube failed. The fact that the tube looks different should not be an issue. I assume that the tube set was matched as per their specs.

When a tube fails, an amp has safegaurds built in to minimize damage to the amp and shut it down. The fuse blew. On some amps, plate and cathode resistors are designed to blow. They act like fuses and protect further damage. If this happens, they will need to be replaced. The heater of the tube will glow but the tube will not work. The auto bias circuit in the 100T is supposed to take care of issues like this and should protect the amp.

One option is to replace the tube and carefully see if the amp works normally. If autobias did its job, everything will be fine. Replacing the tube should reset the bias circuit and the LED's should indicate that all is well. This only happens when the new tube is installed.

If you are concerned that the damage was more extensive, have a tech check out the amp to ensure that any components around the tube in question need to be replaced. Obviously this is the safer option but it will cost you time and money.

Funny you say that. I recently plugged into a pretty full power strip in my drummer's basement, and wonder if that's part of the issue. I'll try a new tube as well. Do burned tubes typically smell? Or blown fuses? That's why I'm concerned about more serious damage.

 

[beans-on-toast]

Funny you say that. I recently plugged into a pretty full power strip in my drummer's basement, and wonder if that's part of the issue. I'll try a new tube as well. Do burned tubes typically smell? Or blown fuses? That's why I'm concerned about more serious damage.

Best to use more than one circuit (on a different breaker) if it is overloaded.

If they blow violently, yes they can smell. A fuse normally melts inside, but it could crack. I would be more concerned about the circuits around the tube.

Are there any signs of burning on the tube? Did the glass envelope crack? If not, then something else is burnt and the amp should be looked at before trying to replace the tube. Often when there is a smell and or smoke and it isn't from the tube itself, this could indicate that there was circuit board damage.

The first thing that a tech would do is open the amp and look for signs, such as scorch marks, of anything burnt or damaged.

 

[beans-on-toast]

I recently plugged into a pretty full power strip in my drummer's basement, and wonder if that's part of the issue.

I use one of these to check the line power. You could connect it inline with the power strip and it would tell you what the voltage is. If it dips lower than 115V, you know that too many devices are connected to the strip.

Kill A Watt Meter - Electricity Usage Monitor | P3 Ordered it through Amazon. I see that they have a newer model P4455.

 

[DJS]

Best to use more than one circuit (on a different breaker) if it is overloaded.

If they blow violently, yes they can smell. A fuse normally melts inside, but it could crack. I would be more concerned about the circuits around the tube.

Are there any signs of burning on the tube? Did the glass envelope crack? If not, then something else is burnt and the amp should be looked at before trying to replace the tube. Often when there is a smell and or smoke and it isn't from the tube itself, this could indicate that there was circuit board damage.

The first thing that a tech would do is open the amp and look for signs, such as scorch marks, of anything burnt or damaged.

Thanks. The tube definitely has burn marks, and smells like it's burned, but has no cracks that I can see. Once I find a new tube, I'll gently power up and see what happens. My gut feeling is that it's only the tube.

 

[Moosehead1966]

Let's hope the above explains and sorts out your issue. When my 100T acted up, tubes continued to cherry out. Rob got things sorted out and in February 2014, the board and bias circuitry was replaced. No problems since . Please keep us informed DJS.

Marc