18 yr old amp...time to replace stuff?

[FILTHnFEAR]

Had my H&K Tube 100 since '97. It was made in '96. I haven't had anything done to it except tube changes.

Now, it's not giving me any problems whatsoever, but I'm gonna be putting some E34l's in it here pretty soon as well as new preamp tubes and I'm wondering if I should have some things replaced. Or at least checked out when I take it to my tech.

 

[TheWarAgainstTime]

I wouldn't worry about it since it hasn't given you any problems, though a proper diagnosis certainly wouldn't hurt

 

[FILTHnFEAR]

Will do. Thanks.

 

[tedtan]

Have your tech check the capacitors. A lot of times older capacitors (around 15-20 years old) will start leaking and they can be leaking before you hear any issues with your amp. This should be a trivial and cheap thing for your tech, especially since your amp is already in for re-tubing and biasing.

 

[glpg80]

If you play the amp on a regular basis, there is no visible bulging of the electrolytic capacitors, and the tech scopes the amp post-rectification to see the worst case Vpp ripple is within tolerances for the brand of capacitors used, then nothing else needs to be done. An advantage of these guitar amps using 1950's technology is that they are damn near bulletproof and need very little care if used properly and frequently.

Normally you do not re-cap an amplifier until it needs it. I will say however, at 20 years old it is a good practice to go ahead and re-cap anyway. Preventative measurements are always a good practice. I see people all the time hunting down old EVH block letter 5150's, but those old birds are past overdue for a full overhaul. Many of them were made 1992-1996.

So yeah. The parts are not expensive, it is the labor that will get you. Talk to your tech.

 

[FILTHnFEAR]

Thanks for the replies gents.

If I was to have capacitors replaced would it improve tone even if they aren't giving me trouble yet?

And @ glpg80, just out of curiosity, why do capacitors leak and what are they leaking? Also, what is the difference between the 50's technology and modern amplification?

Dumb dumb here, if you didn't notice.

 

[glpg80]

Capacitors work due to electric fields being created internally between sandwhiched conductive material and an insulator material. Over time the insulation material breaks down. Any internal gel used to help control arc-overs/general life span can also dry up which further avalanches the problem.

There is no perfect insulator and electrons still get through simply by how electrolytic capacitors work. It is also possible to polarize the insulation material. All of these factors cause leakage current. Because the gel materials break down, the capacitors are more prone to overheating, which causes casing distortion. As time continues, the amount of heat dissipated is inversely proportionate to the efficiency of the capacitor. Eventually they can no longer store energy in the form of electric fields, which electrons are no longer attracted to the plates, and this further decreases efficiency. It's pretty much a downhill slope from there.

 

[neoclassical]

You're gonna need a cap job. They have a shelf life of 10 years and then a service life of 10-15.Those figures may not even be for new caps and not ones made to spec/quality from "the good ol' days."

 

[vick1000]

The advantage of not using FETs (solid state amps) for amplification, you can swap the old tubes for new ones anytime you wish. That leaves the capacitors as the only component with a fixed life span, in the entire circuit. Usualy the filter caps go first, you will get some 60 cycle hum coming through when they start to go bad.

 

[FILTHnFEAR]

^^^ I do notice a little bit more hum going on. Not terrible or anything, but more so than it used to.