Fender Bassman 100T Chapter 3

[NOLA Bass]

Spent the weekend before last in the studio. Clean signal through a REDDI preamp. Dirty signal from my 100T in silent recording mode. Used my Darkglass B3K into the Overdrive side of the amp (basically dialing in some dirt from the amp and from the pedal, I really love the mixture that gives).

 

[Levitamin]

Hej män, would you mind sharing your combination of tubes you swapped? I'm interested in the nicer / more gradual breakup. Cheers from Berlin, will be comparing my 800 to the 100T today!

I discovered that the rattle in my 100T was a couple of the old GE 6L6 tubes I put in . I ordered a quad of Tung Sol 7581a power tubes on the recommendation of a tech. He said they have higher clean headroom and are more rugged. Those might be a good option for your 100T.

 

[Levitamin]

The Bassman 100T sounds great with the 7581a tubes. However, I've already noticed a little bit of tube vibration and there is vibration coming from the rear panel of the 115 neo cabinet. I'm pretty sure it's the horn level knob. It's most pronounced when I sustain a high E note on the D or G strings. I would never notice this stuff in a band situation, but in recording I definitely would. Can anybody recommend a decent absorber to put between the head and cabinet? Thick foam rubber or one of those Auralex isolation pads?

 

[rodl2005]

I'd probly remove the tweeter knob on the rear of the cab and put a little paper over the knob's post... I've hadda do this on other things.... not my Neo 115s... and it's worked out well.

Glad to hear the amp is sounding great.

 

[Levitamin]

I'd probly remove the tweeter knob on the rear of the cab and put a little paper over the knob's post... I've hadda do this on other things.... not my Neo 115s... and it's worked out well.

Glad to hear the amp is sounding great.

Yeah, I'm pretty surprised that I'm having these kinds of issues from a cabinet that is less than five years old. But it's not a huge deal.

 

[rodl2005]

Agreed... you shouldn't be at all.... still under warranty?
I've had no issues from either of my 115 neo cabs.... touch wood.
Anyway... I hope it's a simple fix for you.

 

[Levitamin]

Agreed... you shouldn't be at all.... still under warranty?
I've had no issues from either of my 115 neo cabs.... touch wood.
Anyway... I hope it's a simple fix for you.

No, I bought it used. It's just that it's not that old and seems to be in excellent condition inside and out.

 

[yazzmaster]

Hello Bassmen and women,

I'm hoping you can help me fix an issue I'm having. I recently purchased a used 100T and 410 Neo cab. When I demoed it at the buyer's place, it sounded fine. We couldn't turn it up too loud because he lived in an apartment building. When I brought it home and set it up, it wouldn't get anywhere near to what I imagine 100 watts sounds like. It is extremely quiet. I have to turn both the master and gain (volume) to 10 to get something audible. It is breaking up with the gain that high so I know it's not an issue with the preamp tubes. I confirmed this by connecting the amp to my audio interface and recording from silent mode. It sounded great there.

The auto bias system is telling me all the output tubes are fine. They are all solid green. I even rearranged the 6L6 tubes and that didn't change anything. I've tried different cabs with the head, different heads with the cab, different speaker cables etc. I've basically ruled out everything else as a possible issue.

I've read the manual and I've read many pages of this thread and the previous two threads and haven't seen this particular problem come up. Has anyone dealt with this issue? I've ordered a matched quartet of Tung-Sol 6L6GC STR tubes to try out as a replacement. While I'm waiting for those tubes to ship, is there anything else I can try?

 

[frankzelf]

Try the effects loop, insert a jack cable from sent to return, see if anything changes.

 

[rodl2005]

It ain't in 25w mode is it?

 

[coreyfyfe]

It ain't in 25w mode is it?

As much as it seems a silly question I was going to suggest checking this as well. Maybe move the switch back and forth a few times and make sure.

 

[frankzelf]

Seems not very likely to me, it can be pretty loud for 25 Watts!

 

[beans-on-toast]

Getting the tone settings right can make a differnce in terms of the volume level. Flat is center position, knobs in, on your amp.

Make sure that the impedance switch is properly set for your speaker cabinet. As was suggested for the power setting, reset the switch just to be sure. The Fender neo 410 is 8 ohms as I recall.

 

[yazzmaster]

Getting the tone settings right can make a differnce in terms of the volume level. Flat is center position, knobs in, on your amp.

Make sure that the impedance switch is properly set for your speaker cabinet. As was suggested for the power setting, reset the switch just to be sure. The Fender neo 410 is 8 ohms as I recall.

Yes, it is definitely in 100 watt mode and the volume still would be extremely quiet for 25 Watts. I’ve tried toggling between all modes too. Like I mentioned earlier, it is barely audible with the master and gain at 10. The impedance switch is definitely at 8 ohms.

 

[beans-on-toast]

Yes, it is definitely in 100 watt mode and the volume still would be extremely quiet for 25 Watts. I’ve tried toggling between all modes too. Like I mentioned earlier, it is barely audible with the master and gain at 10. The impedance switch is definitely at 8 ohms.

There’s clearly something going on.

Normally if the power tube bias light are reading green, ie the tubes can be biased, they are fine. That shouldn’t be the problem.

The suggestion to insert an instrument cable between the effect send and return was a good one and worth trying.

 

[bonin in the boneyard]

Hello Bassmen and women,

I'm hoping you can help me fix an issue I'm having. I recently purchased a used 100T and 410 Neo cab. When I demoed it at the buyer's place, it sounded fine. We couldn't turn it up too loud because he lived in an apartment building. When I brought it home and set it up, it wouldn't get anywhere near to what I imagine 100 watts sounds like. It is extremely quiet. I have to turn both the master and gain (volume) to 10 to get something audible. It is breaking up with the gain that high so I know it's not an issue with the preamp tubes. I confirmed this by connecting the amp to my audio interface and recording from silent mode. It sounded great there.

The auto bias system is telling me all the output tubes are fine. They are all solid green. I even rearranged the 6L6 tubes and that didn't change anything. I've tried different cabs with the head, different heads with the cab, different speaker cables etc. I've basically ruled out everything else as a possible issue.

I've read the manual and I've read many pages of this thread and the previous two threads and haven't seen this particular problem come up. Has anyone dealt with this issue? I've ordered a matched quartet of Tung-Sol 6L6GC STR tubes to try out as a replacement. While I'm waiting for those tubes to ship, is there anything else I can try?

Because the problem manifested itself after you physically moved the unit, my first guess would be a connection broken or loose. You're re-seated all the tubes and silent record works, so at least part of the power amp seems to be working well enough at 25W, through the output transformer, and into the power soak. I would guess the tubes and at least part of the transformer are doing their jobs. If one of the secondary windings of the transformer were broken or shorted, then another of the output impedance settings should still yield decent sound even when mismatched with the speaker load; if not at full volume, then reasonably close to it.

I guess I would inspect the wires and connections between the output transformer, the output power switch, and the speaker outputs. If nothing is obviously wrong, you will probably need a qualified tech.

 

[yazzmaster]

There’s clearly something going on.

Normally if the power tube bias light are reading green, ie the tubes can be biased, they are fine. That shouldn’t be the problem.

The suggestion to insert an instrument cable between the effect send and return was a good one and worth trying.

Thank you for all your suggestions, everyone. I tried connecting the send and return but it didn't change anything. Still the same very, very low volume. I am noticing that when I take the amp off of standby I am hearing a pop or clinking sounds from what I assume are the tubes. Is this normal for a tube amp?

 

[beans-on-toast]

Thank you for all your suggestions, everyone. I tried connecting the send and return but it didn't change anything. Still the same very, very low volume. I am noticing that when I take the amp off of standby I am hearing a pop or clinking sounds from what I assume are the tubes. Is this normal for a tube amp?

The pop and clinking out of standby is not unusual.

 

[coreyfyfe]

Thank you for all your suggestions, everyone. I tried connecting the send and return but it didn't change anything. Still the same very, very low volume. I am noticing that when I take the amp off of standby I am hearing a pop or clinking sounds from what I assume are the tubes. Is this normal for a tube amp?

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.

 

[beans-on-toast]

Thank you for all your suggestions, everyone. I tried connecting the send and return but it didn't change anything. Still the same very, very low volume. I am noticing that when I take the amp off of standby I am hearing a pop or clinking sounds from what I assume are the tubes. Is this normal for a tube amp?

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.