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tube amp maintenance


mbengs1

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how should a tube amp be taken care of? like every year' date=' does it need to be checked up?[/quote']

 

 

Nothing much with a newer amps. Preamps tubes tend to work perfectly until they don't, so have a few handy on you next gig. Power amps tubes, you can replace and give some new life back into an amp.. You can do a recap on an amp ever decade or longer. I have amps that are 30 years old and seems to be still going strong.

 

When you are moving the your amp from house to car, and then car to the stage, carry it like a baby, strap it down an secure it inside your vehicle, they tend to fly off a seat if you have to break hard.

 

If you have generous friends that are whiling to help you move gear, decline this generous offer and do it yourself. Remember your amp is not a battering ram to open a club door and people that are willing to lend a helping hand might treat your amp different then you would.

 

Knock on wood. I have been playing since the 70's and have yet to have an amp go down, except for one time. I was playing an out side get and was the first one to plug in to a wrongly wired outlet. The company messed up and sent 220 to my electrical out let. I thought the amp was toast, but an internal fuse blew. When i was gigging with and electric guitar set up I carried a spare amp.

 

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Old or new, its a matter of operating hours when it comes to tubes. For caps its a matter of non operating vs operating hours and age.

 

Older caps were only good for maybe 10 years but they also break down more quickly from non use. Tubes used to have a general lifespan and the idea was to change them before failure. Because their actual operating conditions like vibration and number of times powering them up can do more damage then just sitting there running at normal temp, the actual lifespan varies greatly.

 

There are ways a technician can test for fatigue before failure, but for a normal user, its purely best guesswork.

 

If you play regularly and notice a depreciation is sound quality after using the same tubes for a year, then changing the next set in a year might hold true if the hours you use the amp wind up being pretty close. If you only play the amp on weekends vs someone else who uses it nightly, the lifespan can be very different. I've gotten nearly 20 years out of the tubes in my Bassman head using it pretty regularly. If the same tubes were in a combo being rattled by the speakers I may have only gotten a year out of them.

 

Tube types, Tube manufacturers, and the circuits they run in a are big factors too. Even amount the same tube type you can have some tubes that sound great when you first put them in and they depreciate quickly while another set that's maybe not as good sounding may last 10 times as long.

 

Even with everything equal, you can have some tubes that just weren't made as well and fail prematurely. Like a light bulb, the heater may just decide to blow sooner.

 

In all however, tubes today are very durable and very little maintenance is needed. Many of the issues that cause failure with tube amps is similar to other amps and the abuse amps receive moving them around, sliding around in a car, hitting bumps gig to gig is usually a bigger problem getting damaged then they'd see just sitting in the same place.

 

I will say, one of the common chores I'd have to perform servicing tube amps is simply cleaning them. When the tubes heat up, the hot air rises. This draws in cool air from below which also carries dust into the amp.

 

Over time, this becomes a dirty sticky mess. Pots can become contaminated and become scratchy, tube sockets intermittent. A real nasty thing that happens with the amps which have tubes mounted on PC boards is when they get the gunk built up on them, then you get some high humidity and the gunk becomes a conductor for the high voltage. This eventually etches the board with scorch marks turning the fiberglass board into carbon which shorts everything out. The board can also just blacken from heat and become a conductor shorting things out.

 

Having PC boards in a tube amp was a really stupid design. Manufactures don't give a crap. If they get 5 years out of them, your warrantee has long since expired and they make more money repairing them.

 

Best advice if you have a PC mount tube amp, get it checked on some regular basis. Open your amp once a year and blow the dust out just like you would a computer. if you notice any of the circuit boards starting to blacken, take it to the shop before it shorts out. You can wash boards with zero residue cleaner but getting into the tight spots can be difficult so its better left to a pro.

 

Other then that, if you hear any pops or hum, decrease in fidelity, then its time for service. do it before it tanks and you'll save yourself allot of trouble and cash.

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When I was using a Twin Reverb loaded with EVM12L speakers (ancd not moving the amp myself) I had to completely retube annually. Once, I did it half way through a six-night gig and the change was so drastic it felt like my guitar strings were made out of different material.

 

In the fifteen years I played through that amp I must have paid for it a second time in the cost of the tubes.

 

My Yamaha DG80, which replaced the Twin at the turn of the century, has required absolutely zero maintenance in over fifteen years and has provided consistant sound (no degredation) every time I have used it.

 

The very thing that makes tube amps great are also their weakness. Just this past weekend, I gave away a Mesa Boogie Subway Blues because it has tubes in it and I no longer believe they are worth the hassle. The afore mentioned DG80 has all the characteristics that make tube amps great but with none of the associated issues.

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^^^^^ Tube heads don't need retubing nearly as often as a combo due to the speaker vibrations the tube see in a combo.

 

Speaker load is a big factor for power tubes. If you run a higher impedance then the amp was designed for , the tubes can do south in a mater of days or weeks. When I was a kid I didn't know much about impedance and kept blowing the tubes on my Fender head by running it at 16 ohms. Once I figured it out I never had another issue like that.

 

Preamp tubes tend to become microphonic or in many instances develop popping and noise issues depending on the brand of tube being used. Tone can depreciate a but because it happens over a long period of time you may not notice it till you put new ones in and then you get a big bump in tone.

 

I've heard some guys say they get better life out of EL34 tubes when they let the tubes cool down before moving the amp. I guess it depends on how you move the amp. Any amp I've ever owned is usually stone cold by the time I get it to the car so Its something I cant verify.

 

Heat is the big factor however. In bigger tube amps I used to install exhaust fans. They came in handy during the winters when you'd have an unheated rehearsal space. You'd get a bunch of amps in a small room going and within an hour or so the temp comes up enough to where your fingers aren't numb

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Hi everyone..as i think nothing much with a newer amps. Preamps tubes tend to work perfectly until they don't, so have a few handy on you next gig. Power amps tubes, you can replace and give some new life back into an amp.. You can do a recap on an amp ever decade or longer. I have amps that are 30 years old and seems to be still going strong.

 

http://percentagescalculator.com/

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The caps were 40+ years old in my Blackface Bassman when I replaced them about 10 years ago.

They will vary in lifespan depending on how often you use the amp. When caps get used regularly the oxidation layer on the aluminum foil plates remains thick. When amps sit not being run this oxidation layer thins and the plates short and when they do they can take out everything including the power transformer.

 

This used to be a cap.

 

IMG_1745_zpsh36b1vbz.jpg

 

 

You also have normal aging. When caps get old the electrolyte eventually leaks out like batteries.

 

The cap on the left shows the electrolyte that has leaked out. The cap on the right shows a dimple that has pushed out and is getting ready to leak. Cap manufacturers make a relief valve where the aluminum can is thin on the end.

 

 

I always inspect my power caps when Re-tubing and setting the bias. If the dimple are curved inward and you have no signs of hum, the caps are probably OK. If you see dimples, replace the caps. Most only cost you a few bucks each and they are very simple to solder new ones in. A hot glue gun can help secure them. Just be sure you discharge them before going in there. Caps hold a static charge that can be very high. Not much current but they can give you a nasty jolt. Most caps will discharge through the circuitry within a short time after the amps is shut off but its always good to be safe.

 

FT-901%20Blown%20Filter%20Caps.JPG

 

If the cap shorts and the electrolyte boils or is the cap breaks down from aging, the relief vale opens and lest the pressure out slowly so you don't have an explosion like the picture above.

 

103254-4b510ac317eb6ee43a443efb0c73689b.jpg

 

Here's some vintage Mallory caps like I had in my 60's Fender. You can see the bulges on the ends telling you they need replacement.

 

 

 

BandMaster-007.jpg

 

I don't normally touch the small non electrolytic caps in amps unless they show symptoms of needing replacement. Some of the ceramics can last 50 years and still sound as good as they did when they were new because they don't contain corrosive electrolyte. I have some glass and mica caps that have no life expectancy boundaries. Power caps are a different story, especially the old ones that contained cancer causing PCB's. you want to get rid of those before they explode and cause contamination issues.

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