Category Archives: Amplifiers

Bass amplifier, Guitar amplifier, Keyboard amplifier, Power amplifier

Mam … Step away from the super glue.

I just spent and extra 30 minutes time carefully extricating a jack from a circuit board so as not to damage the board because someone attempted to glue the plastic jack back together.

If something breaks on your gear super glue may sound like a good idea at the time, but 99.9% of the time it is not.

Super glue

Most of the time it just makes things 10 times worse than they already were.

It is so useless in electronic repair I don’t use even a small tube of it in two years’ time.

Do yourself a big favor and think at least twice before you try to super glue something.

Randy Morgan …..  Owner & head technician at All Service Musical Electronics Repair

Cleaning controls or “pots”


Almost every piece of equipment be it a keyboard, a mixing board, a guitar amplifier, or an effect unit has some good old fashioned potentiometers (Pots) that at some time in its life will need to be cleaned.

Cleaning controls is a pretty simple process; it is the getting to the controls to clean them that can sometimes be complicated.

Fist a warning about faders or slide controls. Do not clean them unless the absolutely need it, and only use special fader only cleaner, and finish up with some fader lube. If you use anything else the controls will become so stiff you will barely be able to operate them. Even when you use the proper products on them they will still be stiffer than they were before they were cleaned. That is why I advise not cleaning them unless it is necessary.

Fader controls unlike rotary controls can be cleaned without taking the equipment apart. You just spray the fader cleaner in the slot that shaft rides in that the knob it attached to. Then work it back and forth over its entire sweep several times, apply some fader lube in the same way, and you are done.

Cleaning rotary controls requires disassembly of the unit being worked on. Once you have accesses to the controls the process is pretty simple. Most, but not all rotary controls have a slot or other opening on the back, or side that you can spray your preferred brand of control cleaner into.

Clean the controls one at a time, do not spray them all first and then go back and rotate them as it is not nearly as effective as spraying the cleaner into the control and then immediately rotating it vigorously several times over its entire sweep.

Here at the shop we generally clean each control twice, the reason we do this is if you have to spend several ours on cleaning the controls on say a mixing board that you had to pull all the circuit boards on to get to the controls you sure as heck don’t want to have to pull it all back apart because you were not thorough in your first attempt.

A few additional notes on control cleaning.

When cleaning controls on keyboards, and synthesizers be careful not to get any control cleaner in the area of the keyboard display, or the keyboard contacts.

When cleaning controls on guitar amplifiers try not to get any cleaner on the tubes or any of the power resistors.

When cleaning controls on mixing boards there will generally be a lot of cleaner run off after cleaning the controls. Put the board on some old newspapers or something else absorbent and let the cleaner drain off before you put the cover back on it. It generally helps to do this with the mixing board left sitting in a variety of positions to facilitate draining of the excess cleaner out of the mixing board controls.

Randy Morgan …..  Owner & head technician at All Service Musical Electronics Repair

Where should I buy my tubes?

From a reputable source!

Beware! There are a lot of sources for amplifier tubes and name brand alone does not assure you are getting a quality tube.

You should as a general rule avoid the internet tube warehouse type places because often the tubes they sell are seconds of inferior quality. The initial cost may be cheaper, but the repair bill when they take your amp down will not be. The old adage of you get what you pay for defiantly applies here!

Music stores that sell tubes usually sell what they can buy cheap, sell cheap and make a good profit on. Their choice of what to carry is often not based on careful research. For this reason most music stores are not a good source for tube purchases & information about tubes.

Even some repair shops unfortunately will sell cheap inferior tubes because they feel their customers will kick about the price if they don’t do this. What a good repair shop will do is sell the best quality most reliable tube they can obtain at a reasonable cost to the customer. If this means sacrificing some business so be it, because a good repair shop will realize that quality and long term reliability will save the customer far more in the long run than the small amount of money they would save initially by using cheap inferior tubes!

Sorry if it sounds like I am a soap box here, but I am very passionate about providing quality service and reliable products to my customers.

I will never sell or use something at my shop that is not of good quality, poor quality parts make poor quality repairs, which makes for amplifiers failing in the middle of a gig …and that’s no good at all.


Randy Morgan …..  Owner & head technician at All Service Musical Electronics Repair

My new tubes make my guitar amplifier sound so much better; surely this brand must be better than what I had.

Consider the following scenario to illustrate why people think the tubes that they recently had installed in their amplifier whether it be for a guitar amplifier, a bass amplifier, or any other type of tube amplifier are so much better than the brand they had in there before. (In other words how tube rumors get started)

Most people do not change their tubes until they have a repair issue. We find that on a average most tube amplifiers we take in for repair have not had their tubes changed for 2-3 years ! After 2-3 years any set of tubes are not going to sound good in your amplifier. So pretty much no matter what tube is installed now will sound so much better that what you had that you will think the new tubes are best thing since sliced bread. In other words it is not so much the brand of tube that you installed, but the fact that you changed the tubes at all that made the amp sound so much better.


Randy Morgan …..  Owner & head technician at All Service Musical Electronics Repair

What Brand of tubes should I use?

Here is a subject that has a lot of misinformation associated with it.

There are some differences in sound between different brands of tubes you may choose to install in your amplifier. For instance as a general rule Groove tubes tend to provide a much harsher ( edgy ) sound particularly in guitar amplifiers, less so in bass amplifiers than say JJ tubes. However aside from the harshness of groove tubes I find that most of the other main stream brands are similar in sound quality. The one place I find a big difference is reliability. The tubes we use here at the shop are all pre tested and burned in for maximum reliability and sound quality. The JJ tubes that we used to prefer to use in repairs have recently dropped in reliability so we have switched to using tung-Sol tube. So far we have been having excellent results with them in all types of tube amplifiers. There are of course NOS tubes and other rare tubes that have a nice tone and a hefty price tag, but in most situations and for most people they are not worth the hefty price tag. When we do a repair we will of course use any tube that you desire for your tube amp repair, but in most situations find that our customers are very pleased with our choice of Tung-Sol tubes for their amp repair.

Randy Morgan …..  Owner & head technician at All Service Musical Electronics Repair

Tung sol tube

How often should I change my tubes?

Tube picture

If you are using your guitar amplifier or bass amplifier say 4 hours a day 5 days a week = 20 hours per week. Then you should change your tubes every 6 months if you want to maintain the best sound quality. A year ( approx 1000 hours ) should be the absolute maximum on a set of tubes. Yes, they may still light up and produce sound, but it will not be a very good sound.

Randy Morgan …..  Owner & head technician at All Service Musical Electronics Repair

Do tube amps sound better than solid state amplifiers?

Tube amplifiers seem to have garnered a lot of mystique over the years. I hope to be able to sort from of the fact from fiction for you here.

In my opinion … yes whether they are a guitar amp, a bass amp, a home stereo amp, or the more rare tube power amp they have a warmer sound, great dynamics and a more pleasant breakup than a solid state amp. The downside of course is the higher maintenance cost.

Randy Morgan …..  Owner & head technician at All Service Musical Electronics Repair

Fender reissue amps

Fender reissue

According to some people the new Fender reissue amps and the originals do not sound the same.

As of this writing Fender Offer the following reissue amplifiers: Fender 65 deluxe reissue, Blues deluxe reissue, Blues deville reissue, 59 Bassman reissue, 63 Fender reverb reissue, 65 Super reverb reissue, 65 Twin reverb reissue.

I have not had one of each in the shop for repair at the same time to compare them side by side. So I can not say one way or the other, but here are some probable reasons. For some tonal differences.

Here are some of my thoughts derived from my experience as an electronic repair shop providing tube amp repair service over the years. In the course of providing tube amp repair on both the originals and the reissues here is what I have come up with.


First of all let me state that I think Fender has done everything possible to make them as close to the originals as is possible and to my knowledge the schematic matches between the new and the old units.

Production methods and component quality have changed over the years. Resistors for example are much closer to their stated value than they used to be. Which could account for some of the reason on older amps one amp simply sounded better than the same model from the same year. In other words while the circuits were the same the tolerance factor in early component design meant the circuits operated slightly differently from amp to amp. For example a 100,000 ohm resistor with a 10% tolerance meant the resistor could be anywhere between 90,000 and 110,000 that’s a 20,000 ohm window. Capacitors fall into the same category in regards to tolerance. However before you go out searching for old carbon composition resistors and old style capacitors …. the type of resistor is not the issue it is the fact that the values varied. Carbon comp resistors are also much nosier than the new film resistors. As far as capacitors go you do not want old capacitors as they go bad just sitting on the shelf. The electrolyte in them dries up. Other possible differences may include the manufacturing process and materials used in the transformers. As well as materials and processes used to manufacture the speakers. So in summation The new reissue amps are going to all pretty much sound the same from unit to unit. The old original amps are going to have tonal variations due to looser component and manufacturing tolerances. If you want a Fender 65 deluxe , Blues deluxe , Blues deville, 59 Bassman , 63 Fender reverb, 65 Super reverb, 65 Twin reverb or any one of the other many fine amplifiers that fender has produced. Even if you buy an original it will not necessarily sound as good as your buddies down the street does. Can you tweak the new ones .. of course. There are after market transformers, speakers and different tubes that are all going to change the way it sounds. If you want one to sound the same as your buddies original down the street. You are going to have to get your buddies and yours and bring them both in to the shop. Then every resistor and capacitor will have to be measured in his and the ones in yours that are a different value due to tolerance will need to be changed to match. If after that the sound is still not where you want it. Then it would be time for the after-market output transformer, then a different speaker, and possibly different tubes. Then if it still did not sound as good we would know it was just the magic from the 60’s that made them sound so good

Randy Morgan …..  Owner & head technician at All Service Musical Electronics Repair