Monthly Archives: October 2013

Speaker phasing

This is a simple, but important topic.

Speaker

All speakers as most of you know have a positive and a negative terminal. If these terminals are hooked up backwards the speaker will still work, and if only one speaker is used you will probably not even notice the speaker is out of phase.

The problem comes into play when using more than one speaker cabinet, or multiple speakers within one cabinet.

If one of the two speakers is hooked up backwards then the two speakers will be out of phase and when played together they will sound very thin as they are essentially cancelling each other out. This is because one cone is moving out while at the same instant the other is moving in.

In cabinets with multiple speakers it is also important if you have to replace a speaker that you match it up as closely as possible to the original, or replace both at the same time. The reason is if the two speakers have different efficiencies and cone materials then the cones will move at different rates which creates another type of phasing issue.

When hooking speakers up you cannot always rely on the markings on the speakers. I have seen many speakers over the years that the positive & negative leads were labeled backwards.

The good news is that it is extremely easy to check for phasing issues and proper speaker polarity, all it takes is a 9 volt battery.

With nothing else hooked up to the speaker touch the positive lead of the battery to the positive lead of the speaker, and touch the negative lead of the battery to the negative lead of speaker. As you are looking straight into the front of the speaker it should move towards you.

The motion when the speaker pops when you hook up the battery is what you are looking for. . Do not leave the battery hooked up for more than a few seconds at a time.

When doing this with a cabinet you can simply use the input terminals of the cabinet to perform this test.

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

 

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”

Controls

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

Buyer Beware!

The internet is like the old Wild West, pretty much out of control in many respects.

If you are buying something new on the internet please check to see that who you are buying it from is an actual authorized dealer for the product. If they are not there are two possible problems.

One of them being is the product could actually be counterfeit. Yes it is true counterfeiting is not just limited to Gucci handbags any more.

The other is they are second sourcing the product which makes them the original purchaser and you are considered as far as the manufacturer is concerned to be buying it 2nd hand from the internet seller.

In either of these cases the manufacturer will not honor the warranty on the product. In the case of counterfeit products many times the manufacture will require a serial number to order repair parts and if the serial number is not in their system the will not sell the parts to repair it.

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