Power tube "stem" broke off inside socket

Lovely. I just got my new Mark IV head case in, and finished transferring the chassis from my combo. Went fairly well, but as I was trying to put the power tubes back in one of them broke. Specifically, the plastic "stem" that sits in the middle of the circle of pins broke off, and is now stuck up in the center hole of the socket.

I can't get it out with a pliers (more pieces just break off). I see two screws holding the socket in place, but am very leery about taking the socket out to see if I can get the stuck plastic stem out. I'm not a tube newbie, but neither am I an amp tech.

Is there any particular suggestion anyone has, or am I resigned to take it into a tech?

Also, would the tube still be any good? The pins themselves look OK, and the bit of glass I can see beneath where the plastic "stem" broke off looks to be intact.

Edit: some pics:

pull the chassis and push it out. (easy)
vacuum may be lost on that tube... (junk)

Thanks for the quick reply, GIG4FUN.

Would it be worth it to risk trying the tube out, or could it cause possible damage if the vacuum is broke (the glass looks intact)?

SeasonOfPain said:

Thanks for the quick reply, GIG4FUN.

Would it be worth it to risk trying the tube out, or could it cause possible damage if the vacuum is broke (the glass looks intact)?

Click to expand...

see if water goes in there when you hold it under a faucet or submerse it in an icecream container full of water (LOL). If so..throw it away.

I would say try the water test, then dry the tube out inside a zip-lock bag full of silica gel packets. You know those little things you always get in shoes, etc to keep stuff dry? I saved a bunch for drying out small objects that are impossible to towel dry that you need absolutely 100% water free, IE electronics. Leave it in there overnight, pull that busted stem out with a pair of pliers, and I bet your tube is fine. A little less stable, but it's not like tubes do a lot of moving anyway...

Remove chassis and punch out the fragment like gig4fun sez, Looking at the pic showing the vacuum stem still intact inside the tube, I got a beer that says the tube is fine, don't throw it away! Use a sharpie and put a mark next to the socket where the key of the guide pin goes, then mark the side of the tube with something that will leave a distinctive scratch mark, align the two marks and carry on as if nothing happened. I have several vintage tubes that the guide pin is busted, no big deal if you get it in right.

just wanted to jump in here with this:

I just bought 16 of these. I got them today. Outstanding thing to have around. I loaded up the ata cases and am still looking the gear over...

http://www.theruststore.com/200-Gram-Rechargeable-Silica-Gel-Dehumidifier-P56C27.aspx

(I bought the 200 gram)

Very cool, thanks again for all the fast advice!

The stem was easily visible from the top of the removed chassis, and popped right out, as gig4fun predicted. I had a backup pair of Mesa STR440's that I put in until I have time to mess around testing the broken tube. I'm sure the Mesas are colder than the JJ HiGains they replaced, but for now it's working fine. I may just go ahead and order a new set of replacement tubes, as I was about due for a power re-tube anyway and need to depend on the amp for gigging purposes.

This actually happened to one of my rectifier tubes in a road king. The glass looked fine where the stem broke off, only plastic looked damaged so I risked a go at plugging it back in and turning it on. I made ABSOLUTELY certain that I had installed it the right way because the stem that broke also has the "key" that aligns the tube in the socket correctly. So after inspecting the other rectifier tube to make sure I put it in correctly, I turned it on. The amp turned on, popped fizzed, and then turned off.
Turns out I had the tube misaligned by one pin rotation worth. Lord only knows what that can do to a circuit. After sweating and cussing some, I checked the fuse - it was blown. Replaced the fuse, aligned the tube correctly (ACTUALLY correctly this time) and it turned on fine. Been working great since. Whew.

It's annoying as hell when that happens. I consider myself pretty careful in handling tubes, but I had this happen to a brand new JJ EL34 I was putting in a Marshall. Chances are the tube didn't get damaged, but as others said, you'll have to be very careful putting it in.

The Mark III manual actually a has a really good tip for this. Put it in so you think it's right, then turn the mains on, but do not take the amp off standby. If the heater on that tube lights up, you got it right. If not, you got it wrong, but the nice thing is you haven't put more than 12VDC on the tube, so you won't have fried any thing. Turn the mains off pull the tube back out and try again.

The tube will be fine. The real concern is plugging it back intot the socket in the proper orientation.

If the pin is in good enough shape epoxy it back on the tube.

If not proced with caution. If it was a valuable NOS tube I'd use it carefully. If it's a regular new production tube, I'd consider replacing it just so you don't install it incorrectly.

I used a tube with a missing indexing pin in a Fender Champ for years. I also have an old Amperex (?) 6550 that's missing it's indexing pin. It's still a keeper.

Check the link for just the thing you need.

And make sure you use that Sharpie to push out the broken piece. You don't want anything conductive near that tube socket. My 50 Caliber has 426 volts on the plates of the output tubes. Using a screwdriver or something conductive will put that voltage right into you! A "Season of Pain" indeed.

http://www.tubesandmore.com/scripts/foxweb.dll/moreinfo@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?item=P-STKY-1

stomper said:

Check the link for just the thing you need.

And make sure you use that Sharpie to push out the broken piece. You don't want anything conductive near that tube socket. My 50 Caliber has 426 volts on the plates of the output tubes. Using a screwdriver or something conductive will put that voltage right into you! A "Season of Pain" indeed.

http://www.tubesandmore.com/scripts/foxweb.dll/moreinfo@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?item=P-STKY-1

Click to expand...

I have some of those and they're a great idea, but they only work if the keyway has broken off almost flat. If it leaves a nub sticking up like the pic above - which coincidentally looks almost identical to mine - the repair dealie won't slide on all the way, and the tube won't fit all the way in the socket. You could try to break more of the base away, but that's asking for trouble.

Good to know, Bloodspoint. Thanks for the info. If they went through the troube of making a repair part, you would think they would have made it large enough to fit easily :roll:

Good Lord. 11 years later and I find this post after googling "mesa boogie tube broke off in block" because that is what I found when I went to replace the 36 year old tubes in my Mk IIB. I honestly expected "0 results. Would you like some porn instead?" So, now I need to get up the courage to remove the chassis and try to fix this. I really appreciate the footprints to follow, and especially the caution about high voltage.

Here is another thread:https://www.sevenstring.org/threads/part-of-power-tube-broken-off-in-amp.266009/
I really like the post from "Shask" who says "It is just a little piece of plastic. That is just the guide pin from the tube. You dont really even need it. They break off all the time."

Just look at the silvering on the inside of the tube. If it's turned white the glass broke, the vacuum is lost, and the tube is dead.

If the silvering is still silver, put on a socket saver and put that tube back in service. Make sure you position the socket saver correctly.

I think the tube is/was ok, but I did end up replacing it (and the others as well). I don't honestly know what the lifespan of a tube is, or if it degrades over time, but I figure the six tubes are 37 years old. I did keep the original tubes (all of them) . As for the stem piece, I removed the guts from the case (not really at all difficult) and the stem had dropped free and was just rolling around on the board. The amp does sound better, but the potentiometers are still acting up a bit, especially the presence one in the back. I imagine the next step would be to send it off for a vacation in Petaluma.