request for help with MB Roadster combo pre-amp tubes

[urban41]

I need some help with my Mesa Boogie Roadster combo. I love the sound of the amp, but the tubes are giving me serious headaches. Among other issues, the little spring-loaded shields around the pre-amp tubes keep popping off, especially when I'm carrying it in a car and hit a bump. They are an incredible pain to get on, and then they pop off any time they're bumped. It has been more of an issue since I replaced the tubes, so I'm guessing the threads are more worn or stripped. Also, it is a second-hand amp, so god knows why happened before me. My question is: Do I really need those spring-loaded shields on the pre-amp tubes at all? It seems to play fine without one or two missing. Are the shields there for protection or for heat issues (which might be a problem)? Any help you all can offer would be much appreciated. Thanks.

 

[Blaklynx]

I'm not sure what headaches you're getting from the tubes.... you don't really say, so can't guide/help.

As for the covers/shields, they are there for a reason. Here's four off the top of my head; may be true, may be BS:
1. It can help with RF or electrical interference
2. Since it's a combo amp, they also help to keep the tubes in place to prevent them from slipping out under vibration (gravity doesn't stop)
3. To reduce vibration which can cause wear between the pins and terminals of the connector.
4. Minor protection against breakage / pin damage if you accidentally knock a tube.

If they weren't required, why would any manufacture add them? They would want to sell equipment cheaper, not dearer.

As for your issue of the shields popping off:

1. If the shields two tabs are OK, did you push them through the slots on the chassis and give them a 1/4 to 1/2 turn? You need to do this so they don't pop off. If you did turn the shields as mentioned and they pop off, then:
2. Maybe the two tabs that stick out beyond the diameter of the cylinder body need to be bent back out. If they've flattened, they won't grip the chassis when you push the shield in even if you do turn the shield 1/4-1/2 turn.

Think of it like a bayonet mount. A DSLR has a bayonet lens mount. To lock the lens, you have to position it on the camera first and then turn to lock in position against a stop. It's the same with these shields, except they don't lock because there's no stop. If you keep on turning they will pop off at a turn of 180 degrees.

Google preamp tube shields and look at images to understand what the two tabs should look like. This will give you an idea if the tabs on your shields look the same.

-B

 

[Given To Fly]

I need some help with my Mesa Boogie Roadster combo. I love the sound of the amp, but the tubes are giving me serious headaches. Among other issues, the little spring-loaded shields around the pre-amp tubes keep popping off, especially when I'm carrying it in a car and hit a bump. They are an incredible pain to get on, and then they pop off any time they're bumped. It has been more of an issue since I replaced the tubes, so I'm guessing the threads are more worn or stripped. Also, it is a second-hand amp, so god knows why happened before me. My question is: Do I really need those spring-loaded shields on the pre-amp tubes at all? It seems to play fine without one or two missing. Are the shields there for protection or for heat issues (which might be a problem)? Any help you all can offer would be much appreciated. Thanks.

The first time I changed tubes was on my Mesa/Boogie Roadster Combo. I had all of the same frustrations too. Here are the tricks to making life good again with your Roadster:
1. When you change the tubes, turn the amp upside down. This way you are pushing everything down instead of up. I removed all the tubes as well. This gave my hand some space to work with.
2. With the amp upside down, its much easier to see how the spring-loaded shields go over the preamp tubes. This important because on some of the preamp tubes you can't really see what you are doing so you have to feel your way around so to speak. Its also helpful because when the shields pop off they go straight into your hand as opposed to somewhere inconvenient that will probably cause cuts and scrapes to your hands in order to retrieve it.
3. There should be little rubber O-rings that go around the shields and create a seal between the shields and the chassis. These keep everything in place and are much easier to install when the amp is upside down.
4. Good lighting makes everything easier.

That is how I managed changing the tubes and I hope some of the ideas help you too. Good luck!