Blown preamp tube

[jc74868]

I blew the V1 tube in my KH3. Was doing some experimenting with tone, switched out the stock Ruby for a JJ. It seemed fine, but the next time I turned on my amp, that module was dead. This was during soundcheck before a show saturday. Luckily, I was able able pull off the night just using my JF Trilogy.

I just now pulled the module, and the tube was bad (whited out at the end). I replaced it, everything seems ok, but I really didn't mess with it much. I've got a show tonight, so a little apprehensive.

In some respects, I'm not too worried, because I know anything, especially electronic gear, can fail. But I have never had a preamp tube just go out like that. Has anyone else?

 

[eyeball987]

I have but it was way back in my early MTS days. I had 2 RM50 combo's and I was hot swapping mods between them to see what the differences were. I killed a couple pre's doing that.

 

[jc74868]

I have but it was way back in my early MTS days. I had 2 RM50 combo's and I was hot swapping mods between them to see what the differences were. I killed a couple pre's doing that.

I actually didn't "hot swap" them...BUT, didn't screw it down good now that I think about it. I noticed I hadn't even pushed it all the way in, so I pushed it in and screwed it down tight with the power on. Maybe that was it.

I know you're supposed to be able to "hot swap" them, but I just don't really trust that idea and usually am more careful. Maybe my carelessness was the cause.

 

[LoD21]

make sure when you are swapping tubes that you let them cool a minute before yanking. if they are too hot it is rare but possible the pins can loosen and pull out allowing air into the tube to some degree.

as for you apprehension...i would be too. i'd grab a backup head or something from a buddy just for peace of mind as backup. you want to enjoy your gig and not be paranoid the whole time.

 

[MarcoR]

I know you're supposed to be able to "hot swap" them

No, you really shouldn't.

 

[jc74868]

I know you're supposed to be able to "hot swap" them

No, you really shouldn't.

The term "hot swappable" comes directly from Randall. Something I avoid doing though, because it just doesn't seem very safe with hot tubes

 

[Mattfig]

I personally taker the extra precaution of cold swapping my modules...I will usually take some smooth stones and put them in the freezer for a few days. When I pull a module out of the bay I always use some lubricant (KY) and rubber gloves to avoid residual electrical shock risk. I then place the module on a flat surface and lay the rocks around it closely (but not touching it). I wait ten minutes while reciting the MTS Prayer and then take it to a tech to properly remove the tubes...

You can never be too careful...

 

[MarcoR]

I always use some lubricant (KY)

This is a good practice.

 

[Jaded Faith]

There's nothing to worry about at all. What you experienced was a failing tube due to an air leak. The white on the cap is the give away. Either it cracked or a leak developed at a pin. It had nothing to do with your modules or your amp, it was 100% that particular tube only. Nothing to be alarmed over.

 

[jc74868]

Amp sounded great last night. Had no issues. It was also the first night I played using my master volume boost w/attenuator pot that I slapped together a few days ago. I was really just about ready to chunk my Randall until this. It really gives it some balls. Just a tighter low end and fatter lower mids that it needed.