Ask MetaFilter questions tagged with tubes

Not so deluxe. More like deFAIL.

littlerobothead — Sat, 13 Sep 2008 15:25:06 -0800

Guitar amp issues, with a long way between me and a tech. Help me know what to say when I call! I've owned a Blues Deluxe reissue since 1996. Loved this amp to death when I first got it, and still do. I never gigged with it, just used it for practice and noodling. I put it in storage when I moved to an apartment in DC years ago, and now it's out of storage and I want to play it again.

Trouble is, when I turn it on, I get no sound. Often, the channel selector light will come on and a faint pop is heard. If I let the amp sit on standby for a half hour or so, I can play. Other times I let it warm up, and the minute I load the amp with a signal, it clips out on me.

I've fiddled with the tubes a bit, trying some replacements a friend gave me. I've also changed to fuse to no avail. This is my first tube amp, and only the second amp I ever bought, so I'm sort of a tube noob. There's no bias adjustment on this amp, so an old friend via email told me swamping tubes should be like changing a lightbulb.

Is my amp dead, or am I overlooking something?

A Series of Tubes

Tube — Sat, 14 Jun 2008 22:01:47 -0800

What is this mysterious structure? Tonight I was walking through Seward Park here in Seattle with my video camera, looking for the recently reported coyote. I didn't see any coyotes, but I did find this strange structure (Flickr video). I found three of these, just off the walking trail, all positioned under very large trees. A large funnel on top connects to a series of PVC tubes underneath. This is supported by metal stakes driven into the ground. I assume they are used to collect rainwater, perhaps for some sort of environmental quality testing. But is there some significance to their location under large trees? There were no containers found under these structures.

Why, oh why, now and this way..

tmcw — Sun, 28 Oct 2007 12:15:12 -0800

Cursing bad luck: One of the preamp tubes in my Peavey Classic 30 seemed to peter out during practice yesterday. Two hours before my first concert of the year. An awesome friend came in in the clutch, but now I'm puzzled as to what to do. (and have another show on Thursday) So, playing. It was turned fairly high up (Pre at 6-7, Post at 6-7) (note that the scale is 1 to 12). I'm playing fairly loud (with a drummer, and a loop being sent to it), and within a few seconds I lose volume. We all stop, I look at the back of the amp, and one of the three preamp tubes is not showing its beautiful glow. Playing yields a barely audible, really sad sounding chime.

So, I live with it. The weird part is that today, I remembered that perhaps the other channel on the amp is usable (I think I'm incorrect in thinking this, because it isn't a 'true' two-channel amp) Anyway, the amp seems to work, although that tube still isn't glowing. I'm afraid to test it thoroughly, because I keep reading horror stories of this sort of thing (and I've seem some scary stuff happen with vacuum tubes in a photography setting).

So, wtf do I do? I'm thinking I should retube it, and Eurotubes is insanely hyped. At $61 for a retube of 7 tubes (my amp has 4 post, 3 pre), average price seems to be pretty good relative to other shops. And they can deliver in three days.

Or should I just buy one tube? Or am I set to go with this weirdly-working setup?

I'm disregarding bias for the time being because the C30 uses EL84s which supposedly don't need to be biased. But the thing is, I only have had the amp for about 6 months, and it was brand new. So, WTF? Tubes are supposedly usable for years on end, and these only lasted a half. Am I running the preamp too high? is there anything else that could have caused this (fuses?) that I'm not looking at?

Thanks for any guidance.

Throat and ears hurt, but I'm not otherwise sick. ?

penciltopper — Fri, 05 Oct 2007 10:50:14 -0800

Sore throat/neck. Popped ears won't unpop. Not otherwise sick. What's wrong? That spot just below the jawbone, behind the Adam's apple, where the doctor feels for swollen glands?
That is sore, but not swollen.
It feels like there's a tight ring around my esophagus, just above the adams apple. Hurts to swallow.
My ears are wierd, either popped or clogged, and pinch-nose-and-blow isn't clearing them.

I've had symptoms like this before, as parts of a really bad cold or flu, but I'm not otherwise sick at the moment. My sinuses are otherwise clear, etc.

I've always had trouble with my ears popping on planes, etc. Maybe I just have narrow Eustachian tubes.

I've also been diagnosed with hypothyroidism (Hashimoto's) this year, and am taking levothyroxine for it.

In my imagination, something is inflamed/swelling inside my neck, and that's pinching the ends of my Eustachian tubes closed.

Is that even possible? I can't seem to find a good picture of where the tubes terminate at the non-ear end.

I have a doctor's appointment, but my current HMO doctor (soon to be changed) tends to diagnose everything as allergies (don't have any) or just say "It's probably nothing; it'll go away or you'll get used to it"

Educate me, please, smart-type people!

What are the toughest tubes I can get for my (most likely) inappropriate bike tires?

Bengston — Tue, 11 Sep 2007 19:03:27 -0800

What are the toughest tubes I can get for my (most likely) inappropriate bike tires? Ok, so a couple of weeks ago I decided to turn my nice old Schwinn Sports Tourer into a fixed gear bike. To do this I needed to get a new wheel set and for whatever dumb reason I decided to get another set of 27" wheels instead of switching over to the much more common 700 size. I didn't want to end up with another pair of 1-1/4" tires for the bike so I ordered some 27 x 7/8" FasGrip Slicks from Harris Cyclery. Unfortunately they are nearly impossible to get on the rims and require 2 people to push the last bit of them over the edge. Now, just a couple days after getting the bike all setup, I woke up to find a mysterious flat. Despite my ride home the night previous going off without a hitch, when I went to take the bike to school in the morning I found that the valve on the tube was nearly completely torn off. I don't want to have to buy new fatter tires to protect my tubes and end up sinking even more money into this bike, so I am looking for recommendations for a miracle tube that will be tough enough for me not to worry about.

How do you replace preamp and power tubes in a guitar amp?

atmu — Tue, 13 Mar 2007 19:06:54 -0800

How do I replace my preamp and power tubes? I have a Crate V3112. Unfortunately, it seems that my stock preamp tubes have died (the gain fades after a few minutes of playing and there is extra humming). I figured I'd replace both my preamp and power tubes.

I ordered 3 Tung-sol 12AX7's and 4 JJ EL84's to replace the stock Sovtek 12AX7A's and EL84's. Being that this is my first tube amp, I have no idea how to replace the preamp tubes and power tubes.

I understand that all amps are different, but does anyone have detailed instructions on how I can change the tubes myself? The only amp repairman I know of in San Francisco has a 2 week turnaround time.

I don't know if this matters but the new Tungsol tubes are 12AX7, while the stock Sovteks are 12AX7A. Does the extra "A" mean it's incompatible?

Do I need to get the amp professionally rebiased even if I'm replacing the tubes with the same kind?

Here are some specs in case you need them:

OUTPUT POWER RATING
30 Watts RMS @ 6 % THD, 8 ohm load, 120 VAC

POWER REQUIREMENTS
120 VAC, 60 Hz, 35VA
100/115 VAC, 50/60 Hz, 35VA
230 VAC, 50/60 Hz, 35VA

Bonus points if you know a website with pictures or diagrams explaining the installation process.

Storage for small objects

ObscureReferenceMan — Wed, 06 Sep 2006 10:41:08 -0800

Where to get plastic tubing for storage? I'm looking for plastic tubing and caps for storage of small items (small screws, nails, hooks, etc.). Size would vary between 3/8 to 1 1/2 inches in diameter, and 1-3 inches long. I thought maybe hardware stores and craft stores, but no luck. Googling has turned up nothing (I'd do a category search, but not even sure how to categorize this). This place has exactly what I want (including all kinds of caps), but you have to buy large quantities (i.e. several feet per size). I'm counting on you, since you helped me out before - in fact, this place has something close but in glass. Thanks!

What is a "starving plate" design?

goodnewsfortheinsane — Sun, 27 Aug 2006 14:55:34 -0800

In tube ciruitry, what is a "starving plate" design?

Replacing Bike Tubes

still — Mon, 17 Oct 2005 17:58:49 -0800

I need to replace the tubes on my bicycle, how should I go about doing that? It's a standard road bike with the skinny tires. The tires don't accept air and are flat—I've been told I need to replace the tubes, so here I am. The bike store charges $20 plus the tubes to replace them, I figure I could do this on my own. Help and advice? Thanks.