Power Supply Woes
Updated August 21, 2005

An often overlooked problem when any electronic device fails is mostly related to the power supply. This is often bypassed or ignored when troubleshooting a piece of electronic equipment. A power supply converts mains power into usable voltages in your equipment. Usually 5 volts and/or 12 volts and sometimes +/- 15 to 18 volts. There are some other odd voltages that may be used in your equipment but the above are the most common. This pertains to all equipment and not just your ESQ1 or similar keyboard.

There are two main types of power supplies.

1. Linear. Linear supplies are simple to implement but are inefficient as far as power transfer, and usually get warm or hot in normal operation. They are usually only about 50% efficient. This means that if your equipment requires 45 watts of power, there is about 45 watts of heat given off. They are environmentally "quiet", economical and easy to build and troubleshoot, and they use heavy and bulky steel plates, and copper coils in the power transformer. These types of power supplies have been around since the beginning.

2. Switching. Also referred to as an SMPS (switch mode power supply). They have been around for a much shorter time, with hitting the main stream electronics about 1990. They are very efficient sometimes reaching 85% or more. They run much cooler because of this. They are light weight because they do not use a power/isolation transformer. They are environmentally noisier because they actually switch power at frequencies between 60 and 300 kilohertz. Proper design must be implemented to keep noise out of the equipment and isolate the mains from your equipment.

In both types of supplies there are filter capacitors. These capacitors are like small storage devices like batteries that remove any voltage ripple components from the mains AC or the switching frequency. These capacitors have a varying useful life from 5 years to 15 years. Over that period they can and will deteriorate (change capacity value) and loose their ability to hold a charge. The effective values can change as much as 80% and make a piece of equipment almost useless with strange and illogical behavior. The extent of the behavior will be determined by the designers ability to "over design" the power supply to accommodate the continuously degrading values.

What does this mean to users of ANY type of electronic equipment? If you detect abnormal operation of your equipment, always suspect the power supply first. It is the one part of any piece of equipment that has to work the hardest.

What does that mean to ESQ1 users? It means that your ESQ1 is most likely over 15 years old and you are operating on borrowed time. This is not to say that your instrument will die immediately. You could still get a few more years of reliable use before something starts to act up on an irregular basis. It does mean that you may begin to notice strange and unusual behavior such as an erroneous display, readings that seem to change all by themselves, inconsistent operation such as the keyboard not doing the same normal sequence of events, fluctuating or flickering parameter readings, and of course, if it is power supply related, illogical and non-repeating errors. Sometimes the symptoms may go away for awhile.

Contrary to popular belief, the internal ram battery may not be the cause of the above conditions. I have a studio performance ESQ1 that has no battery at all in it and it works flawlessly with the exception of not being able to save my internal patches or user programmable parameters. I just keep all patches saved to the external cart.

The last release of the firmware, version 3.5 is very stable, without any seriously known bugs in the operating system itself. However, the firmware is located on two EPROM chips that can fail after a number of years and this failure should not be discounted.

Another aspect to consider is the mains power. Here in the U.S., the typical line voltage is 110 to 125 volts. It is amazing to see this number change from hour to hour, from day to day, and from season to season. I have seen the voltage as low as 95 volts and as high as 130 volts. Of course, the higher voltage is actually better for a failing power supply as long as heat isn't a problem. The higher input voltage overcomes the power supplies ability to regulate. If you had a weak power supply and the line voltage dipped below 105 volts, your ESQ1 could definitely start acting up. If you live in an area where the voltage is high or normal in the morning and you tested your ESQ1, you may not notice anything wrong. Let's say that during that summer evening with all the air conditioners running in your town you went to use the ESQ1, you could notice all kinds of problems with it. You're ESQ1 is a prime candidate for a power supply repair. I've seen traveling musical groups take along a voltmeter to monitor their voltage so they can eliminate mains power as their problem in troubleshooting their musical equipment problems.

One other point. The analog or audio portion of your instrument is isolated from the digital portion using a separate power supply or separate regulator portion and one cannot say that since they don't "hear" a hum on the output that all is well with the power supply. The digital portion draws significantly more power and any ripple or regulation problems will not be noticed on the audio since there is good isolation between the two supplies.

The capacitors that are in question are typically called "aluminum electrolytic" capacitors. They come in various sizes and most of them are covered with a thin plastic layer either black, dark or light blue with leads coming out of either one end or one lead out of each end. Some big capacitors such as those in power amplifiers are the size of a beer can and have screw terminals on the end. The ones we are concerned about in your ESQ1 are about 3/4 inch (2 cm) in diameter and 1 inch (2.5 cm) tall.

Typical aluminum electrolytics used in linear and SMPS power supplies. These are called radial since the leads come out of one end. The smaller ones cost about $0.30US and the large ones about $2.00US in small quantities.

In depth description of the ESQ1 Power supply.

The ESQ1 power supply is an analog (analogue for all you EU's) power supply. It uses one power transformer and has three secondary windings to derive the voltages needed. The secondaries are individually fused. Two connectors provide the power to the main board and the display board. The main board requires 5 volts for the digital logic and + and - 12 volts for the analog (audio) circuits. A voltage quadrupler boosts one of the secondary outputs to 36 volts to provide power to the fluorescent display.  There are two separate grounds to keep noise at a minimum. The 5 volt ground is called DGND (digital ground). The +/-12 volt ground is called AGND (audio or analog ground). Electrically they are the same ground but the way it is routed minimizes digital noise from getting into the audio circuits.

There are three voltage regulators, 7805 for the 5 volt supply, 7812 for the +12 volt supply, ans 7912 for the -12 volt supply. These voltage regulators are physically bolted to the rear fin heatsink. Since the demand for current is somewhat higher than the 5 volt regulator can provide, two 51 ohm resistors are shunted across the regulator to "cheat" a little and take some of the dissipated current away from the regulator. 

Two transistors are in the high voltage (36 volt) circuit to switch on the 36 volts only when the 5 volts is being supplied. The ESQ1 power supply is quite robust and once the unit has been "broken in", it should provide may years of reliable service. The weak link in the power supply (as with all supplies) are the filter capacitors. They have a life expectancy of about 10 to 15 years and will dry out eventually. When they do, the regulators will become unstable and cause erroneous operation of the ESQ1 such as flickering display, loosing patch settings, and many other illogical operations. A hum on the audio output may not be heard like other types of audio products because the +/- 12 volt supply is isolated from the 5 volt digital supply.

As a preventive measure, all the large capacitors in the power supply should be replaced at least once in the lifetime of the ESQ1. Four capacitors are a must. C1 (3300uf/25v), C8( 3300uf/25v), C17(4700uf/16v), C18(4700uf/16v).

The voltage multiplier is not as important but since you will have the power supply board out, you might as well swap them out too. C10(100uf/35v), C11(470uf/63v), C12(220uf/35v), C13(470uf/63v).

All the capacitors shouldn't cost more than US$10 total. They are polarized, meaning they must be installed the right way. If you look at the picture of the capacitors above, you will notice that there is a marked wide line going the length of the body. This is the negative (-) lead. Most times the wire leads are different lengths. The longer lead is normally the positive lead. When removing the old capacitors, note the polarity of the capacitor before you remove the old ones. Make sure you install the new ones correctly. If installed reversed, the capacitors will actually explode and leave a real mess around the board. Eyecare caution should be taken when powering the unit up for the first time after replacing capacitors.

If you have never replaced components like these, I recommend you find someone that has done something like this before. Its not worth destroying your ESQ1 by attempting to do it yourself. If you know of a friend or neighbor that is an amateur radio operator, he will most likely be able to help you out and may not even charge you for his work. Amateur radio operators are scattered all over the world and if you happen to see a home with a lot of antennas or towers, you may be in luck. Going to a TV/electronics repair shop may work but you may have to pay a stiff price for their labor. Also check out the local community college and broadcast radio station too.


This portion of the web page is incomplete at this time (April 4,2005) and I will post pictures and procedures for you to test your ESQ1 so you or someone with technical skills may be able to determine and/or repair your ESQ1 power supply.

Rick C.

(c) 2005 Rick C.