Fender Bassman 100T Chapter 3

[beans-on-toast]

If you've tried the loop already I'd check the preamp tubes. There are three 12A_7 tubes, the first 12AX7 is a shared stage between channels 1 and 2 and the preamp recovery on channel 1, the second 12AX7 is the overdrive on channel 2, the 12AT7 is your phase inverter.

If the issue is on both channels it would have to be a problem with V1 or V3 if it was a tube. Pull the 12AX7 from V2 and move it to V1, see if you get volume back on the channel 1. If that doesn't work, try a new 12AT7 in the phase inverter position and see if you get proper volume back. If the issue doesn't track with moving any of the preamp tubes around then you should bring the amp for service because you've rulled out all the things you can do at home.

Yes, the driver tube is always good to try changing. If you don't have a spare 12AT7, try a 12AX7 just for a short test.

 

[yazzmaster]

If you've tried the loop already I'd check the preamp tubes. There are three 12A_7 tubes, the first 12AX7 is a shared stage between channels 1 and 2 and the preamp recovery on channel 1, the second 12AX7 is the overdrive on channel 2, the 12AT7 is your phase inverter.

If the issue is on both channels it would have to be a problem with V1 or V3 if it was a tube. Pull the 12AX7 from V2 and move it to V1, see if you get volume back on the channel 1. If that doesn't work, try a new 12AT7 in the phase inverter position and see if you get proper volume back. If the issue doesn't track with moving any of the preamp tubes around then you should bring the amp for service because you've rulled out all the things you can do at home.

Yes, the issue is with both channels.

Try plugging your bass directly into the power amp in jack and see if you hear anything.

It would help to test the pre and power amp separately. If you have another amp, take the Fender 100T preamp out and feed that into the power amp of another amp. Similarly, take the pre out from another amp and feed that into the power amp in of another amp.

These are great suggestions! I will try them and report back. Thank you, everyone!

 

[yazzmaster]

Try plugging your bass directly into the power amp in jack and see if you hear anything.

It would help to test the pre and power amp separately. If you have another amp, take the Fender 100T preamp out and feed that into the power amp of another amp. Similarly, take the pre out from another amp and feed that into the power amp in of another amp.

Hey Beans-on-toast, your suggestion worked! I don't know how or why it fixed it, which makes me nervous. But I connected the send of my GK 1001RB into the power amp in of the 100T and I was able to get sound! Pretty good sound, actually. When I disconnected the effects loop, and plugged in directly into the Bassman everything started working normally and has been ever since!!!!

Unfortunately, I then discovered that I have one speaker with a frozen voice coil and another with a significant tear on the edges.

Anyone know where I can purchase two replacement speakers? I haven't been able to find the specific model number for the speaker.

Regardless of this new bad news, I'm very happy the head is working and how it sounds.

 

[beans-on-toast]

Hey Beans-on-toast, your suggestion worked! I don't know how or why it fixed it, which makes me nervous. But I connected the send of my GK 1001RB into the power amp in of the 100T and I was able to get sound! Pretty good sound, actually. When I disconnected the effects loop, and plugged in directly into the Bassman everything started working normally and has been ever since.

Good that you resolved it.

I suspect that there is oxidization on the jack shunt contacts. A shunt is a switch that in this case is normally closed on the jack. The signal passes through the shunt when the jack does not have a plug insertd. If the shunt contact has oxidization on it, it acts like a resistor and lowers the signal level, it can also sound distorted. By cycling a plug in and out several times, which is what you did, it can clean the contact a bit and make the amp work better. Oxidization is something that happens with time, more so if the jack is not being used.

If this is the case with your amp, the solution is to properly clean the jack with Deoxit. Below is an open frame Switchcraft jack showing the shunt and where this one would be cleaned. Some jacks are enclosed and more difficult to see where to clean them. It helps to insert a plug when applying the deoxit so that the shunt opens and the solution can penetrate the contact surface.

 

[yazzmaster]

Good that you resolved it.

I suspect that there is oxidization on the jack shunt contacts. A shunt is a switch that in this case is normally closed on the jack. The signal passes through the shunt when the jack does not have a plug insertd. If the shunt contact has oxidization on it, it acts like a resistor and lowers the signal level, it can also sound distorted. By cycling a plug in and out several times, which is what you did, it can clean the contact a bit and make the amp work better. Oxidization is something that happens with time, more so if the jack is not being used.

If this is the case with your amp, the solution is to properly clean the jack with Deoxit. Below is an open frame Switchcraft jack showing the shunt and where this one would be cleaned. Some jacks are enclosed and more difficult to see where to clean them. It helps to insert a plug when applying the deoxit so that the shunt opens and the solution can penetrate the contact surface.

View attachment 2892711

This is super helpful. Thanks, Beans. I just happen to have bought some Deoxit for a different project so I'm glad I can use it here too.

 

[Freight Train]

Hello Bassmen and women,

I'm hoping you can help me fix an issue I'm having. ... snip ... is there anything else I can try?

The only time my 100T did anything remotely like this was when I accidentally used the extension speaker output rather than main.

 

[yazzmaster]

Okay, so apparently Fender isn't directly selling replacement speakers for the Bassman 410 Neo cabs. Can I just purchase two Eminence's 10" Deltalite II 2510 Neo speakers from the Eminence website even though they may not be exactly the same as the other two Eminence speakers in the cab?

 

[beans-on-toast]

Okay, so apparently Fender isn't directly selling replacement speakers for the Bassman 410 Neo cabs. Can I just purchase two Eminence's 10" Deltalite II 2510 Neo speakers from the Eminence website even though they may not be exactly the same as the other two Eminence speakers in the cab?

Does that mean that you can have them replaced at a service center?

I would write eminence, explain what you have, amd ask what they recommend as an off the shelf replacement.

 

[rodl2005]

Not to do with the 410 neo but I've read of someone replacing the 115 neo driver with an Eminence 3015 with VERY good results

 

[Spackhead]

Hello all,
I have an issue with the auto-bias, and not one that I've been able to find that anyone else has posted.
I bought my amp from Canada, and after shipping it over, I converted it to 240v (changing the spade plugs and fuse over. I'm not really technical, but can follow instructions).

The auto-bias lights would cycle through all green, but continue to do so for (maybe I waited) ten minutes. They would continue cycling even after switching off the standby. The amp sounds fine. No issues.

I saw a comment about re-seating the tubes, which I did, and now it continues cycling - all green - and when I switch the standby off, they stop cycling, and are all green, and the amp works.

I rang Fender and they had no record of, or solution for, this. They recommend going to a service tech.

Should I try reseating the ribbon cable?
Is it likely to be a serious issue?

Thanks for your help.
Rob

 

[rodl2005]

You say after reseating the tubes they stopped cycling and it works.. I'd just use it. Ymmv

 

[Freight Train]

Hello all,
I have an issue with the auto-bias, and not one that I've been able to find that anyone else has posted.
I bought my amp from Canada, and after shipping it over, I converted it to 240v (changing the spade plugs and fuse over. I'm not really technical, but can follow instructions).

The auto-bias lights would cycle through all green, but continue to do so for (maybe I waited) ten minutes. They would continue cycling even after switching off the standby. The amp sounds fine. No issues.

I saw a comment about re-seating the tubes, which I did, and now it continues cycling - all green - and when I switch the standby off, they stop cycling, and are all green, and the amp works.

I rang Fender and they had no record of, or solution for, this. They recommend going to a service tech.

Should I try reseating the ribbon cable?
Is it likely to be a serious issue?

Thanks for your help.
Rob

Isn't that correct? Mine cycles green as long as it's in standby, then when I switch power on they flash a few times and then go solid green. Sometimes two immediately go green and two flash a few times then go solid, but they definitely cycle while in standby and go solid only when power is switched on.

 

[Tim1]

Isn't that correct? Mine cycles green as long as it's in standby, then when I switch power on they flash a few times and then go solid green. Sometimes two immediately go green and two flash a few times then go solid, but they definitely cycle while in standby and go solid only when power is switched on.

Agree.

 

[Spackhead]

Thanks fellas, I am reassured now.
But I have two 100T's, and on the other one, the lights go solid before I switch off standby.
Maybe it is the one with the problem?
But it works fine. ....
Thanks again.

 

[SoundOfOneHandSlapping]

Hey fellas, just a couple quick recording questions.
I’m going to try recording using the XLR line out on the back of the 100t. Do I need to put the amp in silent mode to use the line out? Is there an ideal line out level I should set the knob to?

I’ve only ever used microphones to record bass amps in the past.

Any advice is appreciated.

 

[NOLA Bass]

Hey fellas, just a couple quick recording questions.
I’m going to try recording using the XLR line out on the back of the 100t. Do I need to put the amp in silent mode to use the line out? Is there an ideal line out level I should set the knob to?

I’ve only ever used microphones to record bass amps in the past.

Any advice is appreciated.

I was just in the studio recently (and went back in the other night to add some bass to a last minute track that we are adding to the upcoming record. Anyway, I used silent mode. I want to say the level on the back was around 4 or so. I had the master at about 5 on the front. Of course, all that could totally change based on what you are going into in the studio. However, I can say the silent record mode worked outstanding (was using it for my dirt channel) with my cleaner signal going through a REDDI tube DI.

 

[Spackhead]

Hey fellas, just a couple quick recording questions.
I’m going to try recording using the XLR line out on the back of the 100t. Do I need to put the amp in silent mode to use the line out? Is there an ideal line out level I should set the knob to?

I’ve only ever used microphones to record bass amps in the past.

Any advice is appreciated.

Yes, you do have to have the switch on Silent. Otherwise the amp will think it is putting power (volume) out when it has nowhere to go, and will cause problems for your amp.

 

[SoundOfOneHandSlapping]

I have the amp connected to a 410 neo cabinet. I was hoping to record through the line out while hearing myself through the cabinet. I just want to make certain that this is not possible?

Normally I would use headphones connected on the recording end to monitor my playing. However, on this particular track I’m playing with intentional feedback in some of the bass lines. Just thought I could save my ears and have a more natural feel to recording these parts.

Maybe I should just use a mic, but I’m curious to test the capabilities of the amp.

 

[rodl2005]

Of your amps connected to a cab. . I'm sure you don't have to use silent mode...... do ya?

 

[Freight Train]

I have the amp connected to a 410 neo cabinet. I was hoping to record through the line out while hearing myself through the cabinet. I just want to make certain that this is not possible?

Normally I would use headphones connected on the recording end to monitor my playing. However, on this particular track I’m playing with intentional feedback in some of the bass lines. Just thought I could save my ears and have a more natural feel to recording these parts.

Maybe I should just use a mic, but I’m curious to test the capabilities of the amp.

The DI works in Post (power tubes) mode whether you're in Silent Record mode or not. If you want to run a cab along with the DI, set the Output Power switch to whichever power mode you want, 25 or 100 watts. If you're just using the head as a DI with no cab, switch to Silent Record mode.
Tell your engineer you have the level control on the DI and he'll guide you. If he's using a mic pre in it'll probably be in the 2 - 4 range. If he's using a balanced line-level in it may go up to 7 or 8. His proper procedure would be to set the input gain on that channel of the console to optimum level for s/n vs. distortion, then have you adjust the DI's volume control so you're hitting the input at just the right level.