Tech Tips: Tube Amplifier Maintenance

In our new column Tech Tips, Rich Jazmin of Jazmin Electric Co. provides some crucial and often-overlooked info about maintaining and working with your precious gear. This week, he talks about the importance of maintaining your tube amplifiers, some of the telltale signs that it might need maintenance, and some general tips to prevent major malfunctions.

Disclaimer: Tube amplifiers contain lethally high voltages that can harm or kill you if improperly handled, even if the amplifier is unplugged. Any tube amplifier work should be performed by a qualified technician.

Tube amplifiers are wonderful tools, and are just as important in a musical tone equation as the electric guitar; in some cases, they have more influence on shaping and creating your tone than the guitar itself. Plugging a high-end guitar into a small solid state practice amp, in most cases, won’t measure up to the sound of plugging an entry-level guitar into a vintage or hand-wired tube amp. Their dynamic response to the music you play is unmatched by solid state or modeling amplifiers, and are truly instruments in and of themselves. Tube amplifiers utilize lethally high voltages, the interaction between the electrons flowing through the vacuum tubes and big iron transformers lending a magical, somewhat organic playing experience that is much sought after by many guitarists.

Tube amps aren’t without fault, and like many refined instruments and machines, need periodic maintenance to perform at their best and prevent failures - just like changing your car’s oil and giving it a tune-up. With our cars, we understand that changing the oil every 3-4k miles is recommended to keep the car running as it should. However, with tube amps, we don’t have regular maintenance intervals. Despite this, it’s important to understand that maintenance still needs to be performed eventually in order to keep them running smoothly. A lot of questions arise about maintaining tube amps, since we have all been told of the danger caused by their lethally high voltages. With this in mind, here are a few points to keep in mind about tube amp ownership and maintenance.

Tubes

The namesake of the tube amp, the tubes are the first parts of the amplifier that typically first need to be addressed when an amp is starting to act up. This can happen at any time, as the tubes have limited lifespans, similar to a light bulb. They work until they don’t, and it’s difficult to predict when a tube decides that its lifespan is over. Some tubes can last for years and years, but most new production tubes seem to go south within a year or two depending on how much the amp is used and how far it’s pushed during regular use (sustained high volume use tends to wear out tubes quickly, coupled with high physical vibration). Symptoms of tubes that are starting to fail include the following: 

• Noise: Crackling, sputtering, hissing, popping
• Volume fluctuation
• No sound
• Loss of high frequencies
• Microphonics: tubes picking up physical vibration and amplifying it through the speakers, causing noise, feedback, and oscillation
• Red plating: the internal plates of the tube will glow red, distinct from the normal orange operating flow, and will dissipate more noticeable heat around the tube

Smaller preamp tubes can be replaced with no other actions required. However, the larger power tubes - depending on the type of circuit - usually need to be biased after being replaced, which should be performed by a qualified technician with specialist knowledge and proper equipment, as this action is typically performed inside the chassis of the amplifier which is home to all of those lethal operating voltages.

Filter Capacitors

The electrolytic filter capacitors in the power supply section of the amp should be replaced every 10-12 years, by a qualified technician (note: I’ve seen these capacitors go bad within a few weeks past an amplifier’s warranty period, within 3-5 years). These capacitors help to smooth out AC ripple in the B+DC voltage supply that the amplifier operates on. They are high voltage (475-1000 volts DC) and very lethal - enough to put you in the hospital (or in the dirt) if one discharges by touching it. Symptoms of failing filter capacitors include: 

• Noise: popping, crackling
• Volume fluctuation
• Amp sounding like a ring modulator or like there is an effect on the guitar signal
• Loss of low frequencies
• Sound cuts out

General Preventative Maintenance

A few simple things can be done to keep the amp running smoothly and avoid any major failures; even if your tube amplifier isn’t acting up in the ways described above, it can be a good idea to look into preventative maintenance, which is good practice for maintaining any equipment. 

Contact cleaner such as Puretronics aerosol spray or DeOxit can be used on:

• input jacks 
• speaker output jacks
• effects loop send and return jacks/preamp out
• power amp in-jacks
• tube socket pins
• reverb/vibrato jacks
• Footswitch jacks

Other essential preventative maintenance for tube amps includes cleaning to prevent debris such as pet hair, dirt, dust, or spiderwebs from accumulating on your speakers, rear cabinets on combos, or thermal vents on top of cabinets. 

We hope that these tips helped with learning the essentials of tube amp maintenance. If you’re looking for one of those qualified technicians that can safely work on your tube amps, Rich Jazmin is located in Huntington Beach, CA, and can be found at https://www.jazminelectricco.com/  and @jazmin_electric_co on Instagram.

Richard Jazmin is a specialist in guitars and tube amps, and has been playing guitar and learning to maintain them since he was in grade school. He has worked in the industry since high school, assisting Ed Sanner in his guitar and amplifier repair shop, and spent many years touring professionally with the multi-platinum industrial metal band Powerman 5000, as well as playing for Estonian pop singer KERLI. His professional career in the guitar business includes the title of head of the electronics department at LsL Instruments, training by master luthier Avi Shabat, and a few years working at Fulltone Pedals. He currently uses his 30+ years of professional electronics and fabrication experience to run Jazmin Electric Co.