removing tube hold down (spring type)

[lexington125]

I wanted to remove the front panel of my Bassman 135 this evening. Had trouble removing the two screws on the input jack side of the amp as the preamp tubes were in the way. Easy - release the 'tin' tube shields, pull the 3 12A?7 tubes and remove the two front panel screws on that side.

But on the other side, one of the 6L6GC tubes has to be removed to reach the front panel screws. But the 4 power tubes each have these spring loaded 'top-hat' hold downs that I can't seem to remove. If you look at the attached photo, there is a vertical spring on either side of the tube that is screwed down to the chassis at the tube base.



Unless I'm missing something, the two screws need to be removed, to remove the top hat, thus allowing me to pull the tube and reach the panel screws. OK, so turn the amp head upside down and the screw (bolt) on the outside is easily reached. But the other screw is behind the tube. The only way I could see this being removed (or installed) would be if the chassis was outside of the head cabinet. Just like this photo that my tech sent me when he installed the top hats.


It appears that I can NOT remove these hold downs while the chassis is in the head cab. Please tell me that I am clueless and that there is an easy way to remove these hold downs while the chassis is still in the cab. Otherwise I'm stuck - I can't take out the power amp tubes and I can't remove the front panel. That pretty much stops my cleaning effort.

I really hope my ignorance is easily over-ruled by experience. I hate to stop jobs before finishing them......

[The Dude]

Maybe I'm not getting it, but can't you just pull on the retainer and lift it up over the tube?

[Justin Thomas]

Yes, they can be removed with the chassis in. Remove the back panel, pull straight down on the round end portion, and move it to either side. There's one warning - those springs can be quite strong - don't let the retainer portion snap back against the tube glass! I've never broken a tube YET this way, but my time will come. Be really really careful, make sure the tubes are cool. A hot metal spring will make you let go real quick.

I replace the bear claws in my Fenders with this style; yours look nicer than the ones I use! I know there's not much room to work with, but it can be done - I have them in a Bassman AND a Bassman 100.

Of course, those long-envelope JJs don't help at all in an already tight head!

Justin

[lexington125]

As mentioned in the post below, those springs appear to be springs, but act more like a solid bar of metal. I bend bass strings every day, (long scale, heavy strings) but I could not get the "top hat" section to budge. Considering that I am pushing against a thin glass shell, I can't imagine that I could ever exert enough force against the 'hat' to extend the springs so that the hat clears the tube.

I'm too frustrated tonight to continue safely. Accidents happen when you get angry. Tomorrow I try again.

[lexington125]

Thanks for all of the info. Especially the warnings. Tomorrow night I will try again when less angry at the situation

One more question - there is a piece of sheet metal wrapping the side of the tube from the hat to about 3/4" down the side of the tube. Is this meant to stop the hat from sliding off the side of the tube? When I pull down on the top hat (assuming amp is still right side up) will this metal part move with the hat?

Thanks

[The Dude]

Yep, that is part of the top of the retainer. It will "move with the hat" as you say. As Justin mentioned, those long JJ's are probably why the springs feel so tight.

Edit: If they're so tight that you don't feel comfortable stretching them, Usually at the bottom of the spring they are just hooked around a metal tab (by the socket). Maybe you can just unhook them with a needle nose.

[Tom Phillips]

I wanted to remove the front panel of my Bassman 135 this evening...Unless I'm missing something...Please tell me that I am clueless and that there is an easy way to remove these hold downs while the chassis is still in the cab. Otherwise I'm stuck - I can't take out the power amp tubes and I can't remove the front panel. That pretty much stops my cleaning effort. I really hope my ignorance is easily over-ruled by experience...

Man...I always just take the chassis out of the cab before trying to remove the front grill or doing extensive tolex cleaning.

Edit: Even if you remove the power tube at the far side of the chassis, you will still have the power transformer and the rear panel side cleat blocking access to the front panel screws.

[lexington125]

Edit: If they're so tight that you don't feel comfortable stretching them, Usually at the bottom of the spring they are just hooked around a metal tab (by the socket). Maybe you can just unhook them with a needle nose.

First look made me think I had to remove the screw (bolt?) where the spring attaches to the chassis at the tube base. But looking at the photo (above), you may be right. (at work now, no access to amp) One way or another, I wll try to get them off tonight. Hopefully I can succeed without smashing a few power tubes.

[lexington125]

Man...I always just take the chassis out of the cab before trying to remove the front grill or doing extensive tolex cleaning.

Edit: Even if you remove the power tube at the far side of the chassis, you will still have the power transformer and the rear panel side cleat blocking access to the front panel screws.

1. The rear panel side cleat forces me to angle the screwdriver a bit, but only a little. The screwdriver is long enough that the power transformer is not a problem.

2. My plan has been to remove all hardware, front rear / panels, knobs, etc. and clean amp as well as possible. Then take to my tech - he removes chassis from cabinet and keeps chassis for testing and any necessary repairs. I take cabinet home to strip off tolex and re-finish. Bring re-finished cab to tech for final chassis install. As mentioned in earlier threads, when you are working in a small apt with no dedicated work space, removing chassis from head is a challenge, especially with B135, which has really huge, super heavy transformers. I dont want to add more damage to existing bent edges on faceplate.

[g1]

Thanks for all of the info. Especially the warnings. Tomorrow night I will try again when less angry at the situation

One more question - there is a piece of sheet metal wrapping the side of the tube from the hat to about 3/4" down the side of the tube. Is this meant to stop the hat from sliding off the side of the tube? When I pull down on the top hat (assuming amp is still right side up) will this metal part move with the hat?
[ATTACH=CONFIG]38422[/ATTACH]
Thanks

As mentioned, that "wing" will move with the hat. And it is also fairly easily bent, so you can bend it out so it points out to the side. This will mean you don't have to lift the hat as high off the tube.

[Enzo]

I suspect the top part is stuck to the tube. it should pop free, then it is merely a matter of pulling against the springs and moving the cap aside.

Spring retainers have been around for decades, there is nothing special about them, no tricks, you just pull them up to clear and move them aside.

[Randall]

I mean no disrespect, but why does this seem way harder than it should be? It's just a simple spring retainer. If one cannot figure this out, perhaps one should not be messing around with amps. There, I said it. No disrespect intended.

[g1]

That's a legitimate question. I think the concern is due to caution about the delicate glass. I've been queasy also about these sometimes when the springs are real stiff.
But I was also wondering the same as Enzo, maybe the top hat rubbers are stuck.

[lexington125]

And I "don't mess around with amps" _ I just want to clean up the soot / smoke so I take a semi-clean amp to the tech to test / repair any damage from the fire. As the tolex looks shot, I plan on keeping the cabinet while he works on the chassis. Hopefully, when the tech has completed his job, the cabinet will be ready (re-finished) to accept the electronics. I know better than to mess with things I don't understand.

[lexington125]

Steve (tech) or others – I’ve been making good progress cleaning up the amp. But I’ve got a question for you:
With the tall 6L6GC tubes, I don’t see how to remove the spring ‘hold down’ “top hats” while the chassis is in the amp cabinet? I thought that if I loosened the two screws at the tube base, I would be able to remove the spring “legs” but the connector at the screw is a closed loop, not an open “U” shape. I’m assuming that if I completely remove the screws, that there are nuts on the other side that will fall into the chassis? How do I remove the 6L6 tubes without pulling the chassis? There is about 1 inch of clearance between top of tube “hat” and cabinet, but the “hats” have a sheet metal leg that runs down the side of the tube almost exactly one inch – result – NO clearance to remove hat while chassis in cab. see photo.



My goal is to
• completely clean the amp,
• bring it to you
• have you remove the chassis
• you keep chassis for tests and any necessary repairs
• I take cabinet home to either remove tolex and replace, or remove and finish bare wood cab.
• I bring back clean, refinished cabinet and you mount fully tested / repaired chassis
• Amp is then good as new
But if I can’t pull 6L6 tubes, it will limit the amount of cleaning I can do before bringing the amp to you.