BK Butler Tube Amps? CLOSE PLEASE

[Bob Sigafoos]

Any tube can be installed pointing up or down. Horizontal could be problematic . It depends on how the internals of the power tubes are oriented. I’ve seen diagrams on how to orient the key slot correctly if horizontal is your choice. I built a clone of a tweed bandmaster with mis-matched 6L6 tubes installed horizontally that is still going strong after 20 years! The little tube retainers for preamp and power amp tubes are useful but I’ve never had a tube slip or wiggle out of a socket. There’s ways to tighten the gripper thingies inside the tube sockets to make the tube set still.

[Ken Morgan]

Jerry, the tube sets in question were installed in TFL Bandmaster Reverb, 66 Bassman head, and a 71 Twin

[Jerry Overstreet]

This is the type retainer I refer to. Reason for concern is the dead soldier is cracked right about where this clip is. I wasn't sure if that could be caused that way.

I guess I could just bend the clips away so they don't touch the tube?

Anyway, thanks everybody for all the great input. Hope I haven't bored everybody else to death.

You have been a huge help with my understanding of the topic and maybe I'm making too much of many of the various issues and things I read on the net.

I think you have given me enough data so that I can make an informed decision for a purchase. I really appreciate this forum and the forum members taking time to give advice and share the tremendous knowledge that is available here.

[Dave Meis]

The ’bear trap’ retainer like in your pic doesn’t work well with the coin based tubes IMHO, and could cause the damage you experienced. There’s a LOT of heat involved. The spring retainers with the cap that goes over the top of the tube would be my choice..

[Bob Sigafoos]

Any tube can be installed pointing up or down. Horizontal could be problematic . It depends on how the internals of the power tubes are oriented. I’ve seen diagrams on how to orient the key slot correctly if horizontal is your choice. I built a clone of a tweed bandmaster with mis-matched 6L6 tubes installed horizontally that is still going strong after 20 years! The little tube retainers for preamp and power amp tubes are useful but I’ve never had a tube slip or wiggle out of a socket. There’s ways to tighten the gripper thingies inside the tube sockets to make the tube set still.

[Jerry Overstreet]

Update: I picked up a quad of russkie new 6n3C which were marked and the seller listed as a suitable replacement for the 6L6GC. They redplated right away right after switched from Standby. I swapped a different one into the other side of the amp where I was not having any problems and the same thing happened.

They were really reasonable and the seller has a return policy which I may do. I guess the tubes are not matched to the amp. Knowing little about tube amp innards, I'm not going to do too much. I'll probably pull the cover and have a look see for a bias pot even though the info I find indicates it is self biasing...no poking around though...wanna live.
I have meters etc. but I don't really know enough to try any measurements.

I found some info on a similar TW Provalve 60 that says the bias voltage is set by a 1N5261 Zener Diode, so probably no biasing to be done.

The amp seems to run OK with just one tube in the affected side, so I don't know if it's safe to do that. I don't notice anything unusual if it's left on and played for any length of time.

I read somewhere not to do that with a 2 tube circuit...just curious.

Since info is so scarce, I'm not sure what I'll do next...I don't think there's a problem with the amp since the replacement tubes redplate in all positions where the others don't...so, we'll see.

[Donny Hinson]

OK, I have determined these original tubes are 6L6GCR side getter beam tetrode from Shuguang as specified by Mesa Boogie...

Just as a point of information, the location, size, and shape of the "getter" has no effect whatsoever on the sound of the tube (although it can help ID the manufacturer). The getter is there just to eliminate the last traces of oxygen in the tube after it'e been evacuated and sealed.

[Jerry Overstreet]

Update: Through the process of elimination I have determined that there is a problem with the B side or second section of this amp. Closer observation indicates all tubes red plate on this side.

Since I'm not willing to pursue a timely and expensive chase, I contacted the seller and they have agreed to refund most of my investment. Same with the tube vendor.

Therefore, I'm not out a great deal of money and have learned a lot on the subject through the experience.

Special thanks to Bob Sigafoos for your most educational insight, advice, tolerance and patience with my issues and questions here.

Also to a few others who offered some helpful suggestions...Dave, Jim, Ken.

Because a conclusion has been reached, this topic may now be closed.

[Jerry Overstreet]

Close this topic please. Thanks.