Dr.Tube repairs and modifies (tube) guitar amps and other interesting music related analog (non tube) electronic audio equipment. Contrary to the vast majority of other repair shops, who find it is sufficient to repair to the level of "it works again", Dr.Tube goes the extra mile to make an amp not only "work again" but also to make it really sound good again. A subtle but huge difference!
Common guitar amp repairs at Dr.Tube are:
Replacing the tubes. Tubes are subject to wear and tear and have a limited lifetime. A guitar amp with old and worn tubes can hum, sound thin and lifeless, have difficulty "cutting through the mix" and make noise (hiss) and produce crackling noises (fried egg noise).
Replacing the electrolytic caps. Due to the way electrolytic caps are constructed and the high temperatures present in tube amps, electrolytic caps also have a limited lifetime. A guitar amp with worn and dried up electrolytics can hum, have less gain, sound dull and thin, have difficulty "cutting through the mix" and can be troubled by ghost notes. Electrolytics have a maximum life time expectancy of around 10 to 15 years. So with a lot of older amps it is high time to replace these electrolytic caps, even if they look OK.
- Bias mod:
When the power tubes are replaced the bias current (almost always) needs to be set correctly again. This is called biassing. Correct biassing is very important for good tone and a reasonable lifetime expectancy of the power tubes. In cathode biassed amps, like the VOX AC30 etc., this isn't necessary or possible. In (almost) all Mesa Boogie, most Peavey and a lot of older Fender amps there is no bias pot where there should be one. The bias mod is installing a bias potmeter (so that the bias current can be adjusted) and one or more bias measurement resistors so that the bias current can actually be measured.
- Major overhaul:
A classic old Fender, Marshall, Vox, London City (etc.) amp is often more than 30, 40 to 50 years old. Just like an old car such an amp seriously needs a major overhaul. Usually this is a combination of a retube, recap and other maintenance work. After such an overhaul the amp will sound like it did 30, 40 or 50 years ago when it came out of the factory. Dr.Tube uses new but "old style" components for repairs and maintenance so that these amps can be fixed historically and tone correct. In some cases these parts are specially made for Dr.Tube.
These kind of overhauls are often hard work but very rewarding to do.
- JBL D120F & D130F reconing:
Suitable recone kits haven't been available for these classic speakers for many years. Dr.Tube has been able to source very good recone kits for these speakers, so these speakers can shine again! See the JBL D120F & D130F Recone Service page for more information.
Some amps are easier to repair than others. Some notable troublesome amps are:
- Most modern amps
Almost all modern amps are constructed using printed circuit boards (PCB's). This PCB will (very often) need to be removed from the chassis if the need for soldering arises. This is very often the case. This isn't difficult (most of the time) but it can be quite time consuming, requiring removal of the knobs and unscrewing the potmeters and jacks. Sometimes even some wiring needs to be unsoldered first.
- Alle Mesa Boogie amps
Lots of older Mesa Boogie (and some Fender) amps use the well known VacTec VTL5C1 (and other) optocouplers to switch all sorts of matters in these amps. These optos will break down guaranteed one day. These opto's are often stacked upto 4 pieces high and the PCB's are often hard wired to other parts in the chassis, making replacement of an opto quite an arduous task. Luckily this doesn't happen too often (yet).
Almost no Mesa Boogie amp has a bias pot.
Dr.Tube has become the specialist for these troublesome Mesa Boogie jobs.
- The Fender Blues/HotRod Deluxe/DeVille's and the 1990+ amps
These amps have vulnerable PCB's and wiring and use mediocre parts at best. This can make fixing these amps time consuming at times.
- Some modern Laney amps
In some amps Laney uses SMD parts, even between the pins of the tubes on the PCB. A bad idea and a good recipe for hard to find and fix troubles.