Temperature of a 12AX7

[TIMBO]

Hi guys, I been racking my brains for a solution to hold the tubes in loose sockets. I think that there is enough tension on the tube pins to make a good electrical contact but the retainers are loose in the socket. Tubes are upside down.

Wire retainers are an option but this means drilling holes into the chassis to hook the wire into.

The reason I ask the temperature is I was thinking of just putting a couple of small dobs of silicone sealer at the base of the tube.

They say that the silicone is heat resistances is up to 150 degrees C.

I won't put the silicone under the tube just the outer edge.

Thoughts. Thanks

[punkykatt]

Why don`t you use tube shields? They come with a base you attach the the existing 9 pin tube socket.

[tubenit]

And if (for some reason) your sockets don't have a base to accept the shields,  you can use a small L-bracket to attach to each shield and then a shallow sheet metal screw for the foot of the L-bracket to attach to the chassis.

OR ... change out the sockets for ones that will accept shields IF possible.

With respect, Tubenit

[TIMBO]

Hey punkykatt, This is an old amp and it would be a big job to replace the sockets as well some of them are 7 pin and some of the ax7 have the socket retainer inside the chassis. This is why I thought the silicone might be easier.

[TIMBO]

Thanks T, I'm even hesitant to drill a small hole to hook a wire retainer into as there is a lot of components in the area

[TIMBO]

This is the other option http://evatco.com.au/product-list/tube-retainers/retainers-tube/ without the socket ring and hooking the wire through a hole in the chassis.
Most of the problem is the tube vibrating when playing loud causing unwanted noises.

[tubeswell]

Or re-tension the socket clips by gently prising the clip sides together slightly with a small jewellers screwdriver

[HotBluePlates]

The riveted tube sockets are unfortunate... They make a lot of the easier methods of adding tube retainers unworkable.

If it were me, I'd be inclined to drill out the rivets, add nuts/bolts in their place, and use these for mounting the new retainers.

A handheld electric drill, smallish bit and drilling from outside the chassis may make this process less painful.

[TIMBO]

Some wire retainers are on there way. 

[punkykatt]

The riveted tube sockets are unfortunate... They make a lot of the easier methods of adding tube retainers unworkable.

If it were me, I'd be inclined to drill out the rivets, add nuts/bolts in their place, and use these for mounting the new retainers.

A handheld electric drill, smallish bit and drilling from outside the chassis may make this process less painful.

+1   Punkykatt

[thelonious]

TIMBO, looks like you already got your question answered well enough, but for the heck of it I took an IR thermometer to the 12AX7s in my amp and measured about 125F/52C after 10 minutes idle time. My amp is really well ventilated (read: unfinished ). I'm sure they'd get hotter in an enclosed space while driven hard, but probably not up to 150C. My EL84s on the other hand... those measured 236F/113C after the same idle time, and I've heard they get a lot hotter than that when driven hard.

[birt]

i have destroyed lots of things by drilling too deep in all kinds of projects. i always think i have enough control with a handheld drill but no...

so now i use plastic or metal tubes of different lengths to put over the drill bit so it sticks out just enough to go through the enclosure and then can't go any deeper.

[TIMBO]

Thanks guys. 

[tubeswell]

Timbo - so you tried retensioning the socket pin clamps?

[TIMBO]

Hey tubeswell, When I first got the amp and removed the tubes they came out easily not like the sockets of to day. When the amp was ready to fire up, I did push the clamps together and when I replace the tubes I believe there was enough tension on the tube pins to hold them in but I would think that in time they would loosen and the tubes drop out. I even slightly spread the tube pins out to see if that would help, it did to a degree.

I feel there is enough electrical contact not to cause noises.
The other problem is there is a lot of play between the clamps inside the sockets themselves, because of this the tubes thenselves rattle and are causing noises when those power chords are struck.

I think that birt got it with a depth gauge on the drill bit. Thanks